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Dahoas

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<p>I've written a backup script to make a backup of the latest modified files in 12 hours. Basically, it searches two directories for modified files (statically coded) then the <code>find</code> command is used to find the related files. A log file is then created to keep a list of the files. Later on, they are used to form a list of files and these files are used for the backup by tar.</p> <p>Let me know which parts could be developed so that I can improve on and learn new things.</p> <pre><code>#!/usr/bin/env python ''' backup script to make a backup of the files that are newer than 12 hours in the home directory see " man find " " man tar " for more information on the dates and the specific options on how to set different specifications for the selections ''' import sys import os import time if (len(sys.argv) != 2): # if argument count is different # than 2, then there is an error print "Error on usage -&gt; binary &lt;hours_count_back&gt;" quit() else: # convert to integer value hours_back = int(sys.argv[1]) message_start = "Operation is starting".center(50, '-') message_end = "Operation terminated with success".center(50,'-') # print message_start # source directories to check for backup source = [ '/home/utab/thesis', '/home/utab/Documents' ] # find files newer than 24 hours # change to the target directories newer_files = [] # log_file = "log.dat" # cmd to find newer files # than 24 hours cmd_find = "find . -type f -a -mmin " + str(-hours_back*60) + " &gt; " + log_file for directory in source: # iterate over the directories # change to the directory first os.chdir(directory) # apply the command os.system(cmd_find); # files are found with respect to the current directory # change the "." to directory for correct backups c = 0 # process log file files = [] lines = [] log_in = open(log_file,'r') # read lines without \n character while 1: l = log_in.readline() if not l: break # do not include the newline # -1 is for that lines.append(l[:-1]) # for l in lines: l_dummy = l.replace( '.', directory, 1 ) files.append(l_dummy) # extend the list with newer files newer_files.extend(files) #print newer_files print newer_files # date today = time.strftime('%Y%m%d') # current time of the date # possible to do different backups in different times of the day now = time.strftime('%H%M%S') # target_directory = "/home/utab/" target = target_directory + today + "_" + now + \ '.tgz' # do the actual back up backup_cmd = "tar -C ~ -zcvf %s %s" % ( target , ' '.join(newer_files) ) status = os.system(backup_cmd) if status == 0: print message_end else: print "Back-up failed" </code></pre>

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<p>I present you my first ever module to learn some Erlang awaiting your scrutiny . It does a word frequency count using map/reduce . I'm an Erlang noob, so I would very much like feedback about:</p> <p>Unneeded verbosity / code</p> <p>Erlang 'style' mistakes</p> <p>Things that can be done more elegantly</p> <pre><code>-module(main). -export([map/1]). -export([main/0]). -export([reducer_wrapper/1]). -export([reducer/2]). -define(NUMBER_OF_PARTITIONS, 100). main() -&gt; Lines = readlines('pg20417.txt') , lists:foreach( fun main:map/1, Lines ), start_reduce(). %% signals all reducer_wrappers that all emits are received, and the actual reduce can be started start_reduce() -&gt; lists:foreach( fun(PartitionNr) -&gt; get_reducer(PartitionNr) ! start_reduce end, lists:seq(1, ?NUMBER_OF_PARTITIONS) ). %% emits every word with cnt = 1 map(Line) -&gt; Words = string:tokens( string:to_lower(Line), " .,;:\n()?"), lists:foreach ( fun(Word) -&gt; get_reducer( Word, ?NUMBER_OF_PARTITIONS ) ! {emit, {Word, [1]}} end, Words ). %% returns the reducer Pid get_reducer( PartitionNr ) -&gt; ProcessName = list_to_atom( lists:concat( [PartitionNr, '_reducer'] ) ), case whereis( ProcessName ) of undefined -&gt; Pid = spawn(?MODULE, reducer_wrapper, [[]]), register( ProcessName, Pid ), Pid; Pid -&gt; Pid end. get_reducer( Key, NumberOfPartitions ) -&gt; get_reducer( erlang:phash2(Key) rem NumberOfPartitions + 1 ). %% the reducer wrapper proces reducer_wrapper(KeyValueTuples) -&gt; receive { emit, KeyValueTuple } -&gt; reducer_wrapper( [KeyValueTuple] ++ KeyValueTuples ); start_reduce -&gt; Dictionary = lists:foldl( fun main:reducer/2, dict:new(), KeyValueTuples ), show_all( dict:to_list(Dictionary) ) end. reducer( { Key, [Cnt] }, Dictionary ) -&gt; case dict:is_key( Key, Dictionary ) of true -&gt; dict:store( Key, dict:fetch( Key, Dictionary ) + Cnt, Dictionary ); false -&gt; dict:store( Key, Cnt, Dictionary ) end. readlines(FileName) -&gt; {ok, Device} = file:open(FileName, [read]), get_all_lines(Device, []). get_all_lines(Device, Accum) -&gt; case io:get_line(Device, "") of eof -&gt; file:close(Device), Accum; Line -&gt; get_all_lines(Device, Accum ++ [Line]) end. show_all([Head|Tail]) -&gt; io:format("~p~n", [Head]), show_all(Tail); show_all([]) -&gt; void. </code></pre>

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<p>I have a method that gets an RSS feed using LINQ to XML and returns a collection of an object that grabs only the data I need. There's really only one other method in the class I'm concerned about that you'll see in the sample -- RemoveUrlNoise.</p> <p>How do I test a method like this or change it to be more testable?</p> <pre><code> public IEnumerable&lt;PostDetails&gt; GetPostDetails(string rssUrl) { XElement feed = XElement.Load(rssUrl); var items = from item in feed.Elements("channel").Elements("item") select item; return items.Select(item =&gt; new PostDetails { Title = item.Element("title").Value, Url = RemoveUrlNoise(item.Element("guid").Value), PubDate = item.Element("pubDate").Value }).OrderBy(i =&gt; i.PubDateAsDateTime).ToList(); } </code></pre>

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<p><img src="https://i.stack.imgur.com/npc8B.gif" alt="queens"></p> <blockquote> <p>Figure 2.8: A solution to the eight-queens puzzle. The ``eight-queens puzzle'' asks how to place eight queens on a chessboard so that no queen is in check from any other (i.e., no two queens are in the same row, column, or diagonal). One possible solution is shown in figure 2.8. One way to solve the puzzle is to work across the board, placing a queen in each column. Once we have placed k - 1 queens, we must place the kth queen in a position where it does not check any of the queens already on the board. We can formulate this approach recursively: Assume that we have already generated the sequence of all possible ways to place k - 1 queens in the first k - 1 columns of the board. For each of these ways, generate an extended set of positions by placing a queen in each row of the kth column. Now filter these, keeping only the positions for which the queen in the kth column is safe with respect to the other queens. This produces the sequence of all ways to place k queens in the first k columns. By continuing this process, we will produce not only one solution, but all solutions to the puzzle.</p> <p>We implement this solution as a procedure queens, which returns a sequence of all solutions to the problem of placing n queens on an n× n chessboard. Queens has an internal procedure queen-cols that returns the sequence of all ways to place queens in the first k columns of the board.</p> </blockquote> <pre><code>(define (queens board-size) (define (queen-cols k) (if (= k 0) (list empty-board) (filter (lambda (positions) (safe? k positions)) (flatmap (lambda (rest-of-queens) (map (lambda (new-row) (adjoin-position new-row k rest-of-queens)) (enumerate-interval 1 board-size))) (queen-cols (- k 1)))))) (queen-cols board-size)) </code></pre> <blockquote> <p>In this procedure rest-of-queens is a way to place k - 1 queens in the first k - 1 columns, and new-row is a proposed row in which to place the queen for the kth column. Complete the program by implementing the representation for sets of board positions, including the procedure adjoin-position, which adjoins a new row-column position to a set of positions, and empty-board, which represents an empty set of positions. You must also write the procedure safe?, which determines for a set of positions, whether the queen in the kth column is safe with respect to the others. (Note that we need only check whether the new queen is safe -- the other queens are already guaranteed safe with respect to each other.)</p> </blockquote> <p>I found this task to be especially difficult. I think I have a working answer, but I'm sure that there is a much better way. My current solution feels like a popsicle-stick bridge held together with duct tape, poised to fall apart at any moment. I know it's messy, so I must apologize in advance. If you can't follow it let me know and I'll try to rewrite it a bit if possible. For now, though, I need to take a break! How can I improve my code?</p> <pre><code>(define (enumerate-interval i j) (if (= i j) (list j) (cons i (enumerate-interval (+ i 1) j)))) (define (filter f seq) (if (null? seq) null (if (f (car seq)) (cons (car seq) (filter f (cdr seq))) (filter f (cdr seq))))) (define (flatmap op seq) (foldr append null (map op seq))) (define (queens board-size) (define (empty-board) (map (lambda (row) (map (lambda (col) 0) (enumerate-interval 1 board-size))) (enumerate-interval 1 board-size))) (define (adjoin-position new-row k rest-of-queens) (cond ((and (= new-row 1) (= k 1)) (cons (cons 1 (cdar rest-of-queens)) (cdr rest-of-queens))) ((&gt; k 1) (cons (car rest-of-queens) (adjoin-position new-row (- k 1) (cdr rest-of-queens)))) (else (let ((adjoined (adjoin-position (- new-row 1) k (cons (cdar rest-of-queens) (cdr rest-of-queens))))) (cons (cons (caar rest-of-queens) (car adjoined)) (cdr adjoined)))))) (define (queen-cols k) (if (= k 0) (list (empty-board)) (filter (lambda (positions) (safe? k positions)) (flatmap (lambda (rest-of-queens) (map (lambda (new-row) (adjoin-position new-row k rest-of-queens)) (enumerate-interval 1 board-size))) (queen-cols (- k 1)))))) (queen-cols board-size)) (define col car) (define row cdr) (define (indexOf x seq) (define (rec i remains) (cond ((null? remains) (error "No x found in seq." x seq)) ((= (car remains) x) i) (else (rec (+ i 1) (cdr remains))))) (rec 0 seq)) (define (nth n seq) (cond ((null? seq) (error "Sequence shorter than n" seq n)) ((= n 1) (car seq)) (else (nth (- n 1) (cdr seq))))) (define (all-true seq) (cond ((null? seq) true) ((car seq) (all-true (cdr seq))) (else false))) (define (upto k rows) (if (or (= k 0) (null? rows)) null (cons (car rows) (upto (- k 1) (cdr rows))))) (define (safe? k positions) (let ((uptok-positions (upto (- k 1) positions)) (kth-position (nth k positions))) (define (col-row-coords pos) (define (process-row rownum rows) (define (process-col colnum row) (cond ((null? row) null) ((= (car row) 1) (cons rownum colnum)) (else (process-col (+ colnum 1) (cdr row))))) (if (null? rows) null (cons (process-col 1 (car rows)) (process-row (+ rownum 1) (cdr rows))))) (process-row 1 pos)) (let ((col-and-row (filter (lambda (x) (not (null? x))) (col-row-coords uptok-positions))) (k-coord (cons k (indexOf 1 kth-position)))) (define (diagonal? p1 p2) (= (abs (- (col p1) (col p2))) (abs (- (row p1) (row p2))))) (all-true (map (lambda (pos) (and (not (= (col k-coord) (col pos))) (not (= (row k-coord) (row pos))) (not (diagonal? k-coord pos)))) col-and-row))))) </code></pre> <p>EDIT: Thanks for the feedback! I have a new version here. I would appreciate any feedback you have. </p> <pre><code>(define (enumerate-interval i j) (if (&gt; i j) null (cons i (enumerate-interval (+ i 1) j)))) (define (filter f seq) (if (null? seq) null (if (f (car seq)) (cons (car seq) (filter f (cdr seq))) (filter f (cdr seq))))) (define (flatmap op seq) (foldr append null (map op seq))) (define (queens board-size) (define (empty-board) '()) (define (adjoin-position new-row k rest-of-queens) (append rest-of-queens (list (cons new-row k)))) (define (queen-cols k) (if (= k 0) (list (empty-board)) (filter (lambda (positions) (safe? k positions)) (flatmap (lambda (rest-of-queens) (map (lambda (new-row) (adjoin-position new-row k rest-of-queens)) (enumerate-interval 1 board-size))) (queen-cols (- k 1)))))) (queen-cols board-size)) (define col car) (define row cdr) (define (threatens? q1 q2) (define (diagonal? q1 q2) (= (abs (- (col q1) (col q2))) (abs (- (row q1) (row q2))))) (or (= (col q1) (col q2)) (= (row q1) (row q2)) (diagonal? q1 q2))) (define (nth n seq) (if (= n 1) (car seq) (nth (- n 1) (cdr seq)))) (define (except-nth n seq) (cond ((null? seq) '()) ((= n 1) (cdr seq)) (else (cons (car seq) (except-nth (- n 1) (cdr seq)))))) (define (safe? k positions) (define (rec me threats) (or (null? threats) (and (not (threatens? me (car threats))) (rec me (cdr threats))))) (rec (nth k positions) (except-nth k positions))) </code></pre>

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<p>Here's an interesting scenario that I encountered the other day. I did eventually reach a solution on my own. However, I'd welcome any comments and better approaches.</p> <p><strong>The requirements</strong></p> <p>I want to generate JAXB objects based on a collection of XSDs using XJC as part of a Maven build. I'll be using JAXB-RI 2.1 as the implementation.</p> <p>In addition, I want to make sure that all objects implement a signature interface (e.g. <code>MySignature</code>) which has no methods. Also, I want to avoid using <code>XmlGregorianCalendar</code> and have Joda <code>DataTime</code> instead (with a suitable adapter that I'll provide called <code>DateUtils</code> with <code>parse()</code> and <code>format()</code> methods).</p> <p>Finally, I want to be able to select certain objects to act as root elements so I'll need to selectively add <code>@XmlRootElement</code> to some objects, and I have suitable XPath expressions to locate them. </p> <p>I can't make any changes to the XSDs. </p> <p><strong>The approach</strong></p> <p><strong>Step 1</strong> - Configuring the pom.xml</p> <p>Configure Maven to use the XJC plugin as follows:</p> <pre class="lang-xml prettyprint-override"><code>&lt;build&gt; &lt;plugins&gt; &lt;plugin&gt; &lt;groupId&gt;org.jvnet.jaxb2.maven2&lt;/groupId&gt; &lt;artifactId&gt;maven-jaxb2-plugin&lt;/artifactId&gt; &lt;version&gt;0.7.4&lt;/version&gt; &lt;executions&gt; &lt;execution&gt; &lt;id&gt;generate-domain1&lt;/id&gt; &lt;goals&gt; &lt;goal&gt;generate&lt;/goal&gt; &lt;/goals&gt; &lt;configuration&gt; &lt;strict&gt;false&lt;/strict&gt; &lt;schemaIncludes&gt; &lt;value&gt;domain1.xsd&lt;/value&gt; &lt;/schemaIncludes&gt; &lt;bindingIncludes&gt; &lt;include&gt;domain1-bindings.xjb&lt;/include&gt; &lt;/bindingIncludes&gt; &lt;extension&gt;true&lt;/extension&gt; &lt;generatePackage&gt;org.example.domain1&lt;/generatePackage&gt; &lt;generateDirectory&gt;${project.build.directory}/generated-sources/domain1&lt;/generateDirectory&gt; &lt;args&gt; &lt;arg&gt;-Xannotate&lt;/arg&gt; &lt;/args&gt; &lt;plugins&gt; &lt;plugin&gt; &lt;groupId&gt;org.jvnet.jaxb2_commons&lt;/groupId&gt; &lt;artifactId&gt;jaxb2-basics&lt;/artifactId&gt; &lt;version&gt;0.6.0&lt;/version&gt; &lt;/plugin&gt; &lt;plugin&gt; &lt;groupId&gt;org.jvnet.jaxb2_commons&lt;/groupId&gt; &lt;artifactId&gt;jaxb2-basics-annotate&lt;/artifactId&gt; &lt;version&gt;0.6.0&lt;/version&gt; &lt;/plugin&gt; &lt;/plugins&gt; &lt;/configuration&gt; &lt;/execution&gt; &lt;/executions&gt; &lt;/plugin&gt; &lt;/plugins&gt; &lt;/build&gt; </code></pre> <p>The use of a dedicated execution configuration is there to allow additional mutually exclusive XSDs to be built using a different target output path. </p> <p><strong>Step 2</strong> - Configure the bindings</p> <p>Include the following as <code>src/main/resources/domain1-bindings.xjb</code>.</p> <pre class="lang-xml prettyprint-override"><code>&lt;?xml version="1.0" encoding="UTF-8" standalone="yes"?&gt; &lt;jaxb:bindings xmlns:jaxb="http://java.sun.com/xml/ns/jaxb" xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:xjc="http://java.sun.com/xml/ns/jaxb/xjc" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:annox="http://annox.dev.java.net" xsi:schemaLocation="http://java.sun.com/xml/ns/jaxb http://java.sun.com/xml/ns/jaxb/bindingschema_2_0.xsd" jaxb:extensionBindingPrefixes="xjc annox" version="2.1"&gt; &lt;jaxb:globalBindings&gt; &lt;jaxb:serializable uid="1"/&gt; &lt;!-- All generated classes must have MySignature interface (supplied in dependencies) --&gt; &lt;xjc:superInterface name="org.example.MySignature"/&gt; &lt;!-- All temporal fields are implemented as Joda DateTime and use DateUtils as an adapter --&gt; &lt;jaxb:javaType name="org.joda.time.DateTime" xmlType="xs:time" parseMethod="org.example.DateUtils.parseDateTime" printMethod="org.exmaple.DateUtils.formatDateTime" /&gt; &lt;/jaxb:globalBindings&gt; &lt;!-- Application of annotations to selected classes within schemas --&gt; &lt;!-- org.example.SomeRootType @XmlRootElement --&gt; &lt;jaxb:bindings schemaLocation="domain1.xsd" node="/xs:schema"&gt; &lt;jaxb:bindings node="xs:complexType[@name='SomeRootType']"&gt; &lt;annox:annotate&gt; &lt;annox:annotate annox:class="javax.xml.bind.annotation.XmlRootElement" name="SomeRootType"/&gt; &lt;/annox:annotate&gt; &lt;/jaxb:bindings&gt; &lt;/jaxb:bindings&gt; &lt;/jaxb:bindings&gt; </code></pre> <p><strong>Troubleshooting</strong></p> <p>If you encounter the infamous</p> <blockquote> <p>Unsupported binding namespace "". Perhaps you meant "<a href="http://annox.dev.java.net">http://annox.dev.java.net</a>"</p> </blockquote> <p>then you need to examine your <code>bindings.xjb</code> to make sure that you're using the correct namespace URIs (as defined above) and have included them into <code>extensionBindingPrefixes</code>.</p>

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<p>It seems to play up sometimes and I'm not sure if this is due to the class itself or the way I'm using it. Can someone confirm that this is a 'good' implementation of a <code>VertexArrayObject</code> class?</p> <pre><code>//The following code is public domain public class VertexArray : GraphicsResource { protected readonly int ID; DrawMode _drawMode; VertexLayout _vertexType; protected BufferUsageHint bufferUsage = BufferUsageHint.StaticDraw; int vertexCount; int vertexBufferID; public DrawMode DrawMode { get { return _drawMode; } set { _drawMode = value; } } public int VertexCount { get { return vertexCount; } } public BufferUsageHint BufferUsage { get { return bufferUsage; } set { bufferUsage = value; } } public VertexArray() : base() { ID = createVAO(); disposed = false; } public VertexArray(DrawMode drawMode) : base() { _drawMode = drawMode; ID = createVAO(); disposed = false; } int createVAO() { int id; GL.GenBuffers(1, out vertexBufferID); GL.GenVertexArrays(1, out id); GL.BindVertexArray(id); GL.BindBuffer(BufferTarget.ArrayBuffer, vertexBufferID); VenGFX.currentVAO = this; return id; } public void Bind() { if (vertexCount == 0) throw new Exception("Vertex buffer has no data, and therefore can't be used"); if (disposed) throw new ObjectDisposedException(ToString()); GL.BindVertexArray(ID); VenGFX.currentVAO = this; } public void SetData&lt;T&gt;(T[] Array) where T : struct, IVertex { GL.BindVertexArray(ID); if (Array.Length &gt; 0 &amp;&amp; Array[0].Layout != _vertexType) setVertexType(Array[0].Layout); GL.BindBuffer(BufferTarget.ArrayBuffer, vertexBufferID); GL.BufferData(BufferTarget.ArrayBuffer, (IntPtr)(Array.Length * _vertexType.SizeInBytes), Array, bufferUsage); vertexCount = Array.Length; VenGFX.currentVAO = this; } public void SetData&lt;T&gt;(T[] Array, int length) where T : struct, IVertex { GL.BindVertexArray(ID); if (Array != null &amp;&amp; Array.Length &gt; 0 &amp;&amp; Array[0].Layout != _vertexType) setVertexType(Array[0].Layout); GL.BindBuffer(BufferTarget.ArrayBuffer, vertexBufferID); GL.BufferData(BufferTarget.ArrayBuffer, (IntPtr)(length * _vertexType.SizeInBytes), Array, bufferUsage); vertexCount = length; VenGFX.currentVAO = this; } void setVertexType(VertexLayout layout) { _vertexType = layout; layout.Set(); } protected override void Release() { if (VenGFX.currentVAO == this) { GL.BindVertexArray(0); VenGFX.currentVAO = null; } int id = ID; GL.DeleteBuffers(1, ref vertexBufferID); GL.DeleteVertexArrays(1, ref id); } } </code></pre> <p>To draw with it, I write</p> <pre><code>if (mesh.VertexCount == 0) return; if (currentVAO != mesh) mesh.Bind(); GL.DrawArrays((BeginMode)(int)mesh.DrawMode, 0, mesh.VertexCount); </code></pre>

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<p>I am quite new to Java and was trying to improve my skills a little by doing a binary file reader. The choosen one was the <a href="http://en.wikipedia.org/wiki/Type-length-value" rel="nofollow">TLV</a> format. I've chosen that one for being reasonably simple, but not so simple. Also I had some concrete examples with good documentation which I could follow for decoding.</p> <p>The reader works, but I ended up with a class that seems way too big to be right. I wonder if anyone can break down this code into something more robust.</p> <pre><code>package tlv; import java.io.BufferedInputStream; import java.io.DataInputStream; import java.io.File; import java.io.FileInputStream; import java.io.FileNotFoundException; import java.io.IOException; import java.util.ArrayList; import java.util.Iterator; import tlv.errors.MissingI10ParameterException; import tlv.errors.ParseI10ParameterException; import tlv.errors.TLVFileException; /** * Represents a TLV file. * Expects class File, which represents a TLV file formated as: * [HEADER] * [LogicalBlock-1] * [DataSegmentHeader-1] * [DataSegment-1] * [DataSegmentTrailer-1] * (...) * [DataSegmentHeader-n] * [DataSegment-n] * [DataSegmentTrailer-n] * */ public class DiriTlvFile { ArrayList&lt;LogicalBlock&gt; dirisegs = new ArrayList&lt;LogicalBlock&gt;(); int tbc = 114; public DiriTlvFile(File tlv) throws TLVFileException { DataInputStream dis = null; try { // Here BufferedInputStream is added for fast reading. dis = new DataInputStream(new BufferedInputStream(new FileInputStream(tlv))); // Header data byte[] ba = new byte[3]; /* This is the fixes header added We just skip it straight away. */ dis.skipBytes(114); LogicalBlock lb = null; // Iterate over main file parts while (dis.available() &gt; 0) { if (dis.read(ba, 0, 3)!= 3) throw new TLVFileException("Error reading DataSegmentID (wrong byte count) @" + tbc); tbc += 3; String headerId = new String(ba); // File header if (headerId.equalsIgnoreCase("I01")) { lb = new LogicalBlock(); // Skip uninteresting part of header dis.skipBytes(50); tbc += 50; // Data Segment body } else if (headerId.equalsIgnoreCase("I10")) { if (lb == null) throw new TLVFileException( "Logical Block was not initiated! (Missing I01 structure in file)."); byte[] dsheader = new byte[25]; if (dis.read(dsheader, 0, 25) != 25) // Head of the DS throw new TLVFileException( "Error reading DataSegmentHeader (I10, wrong byte count) @ " + tbc); tbc += 25; int dssize = (dsheader[24] &amp; 0xFF) - 1; // Size of DS body (+the header itself?) byte[] dsbody = new byte[dssize]; // Body of DS // Read DataSegmentBody if (dis.read(dsbody, 0, dssize) != dssize) throw new TLVFileException( "Error reading DataSegmentBody (I10, wrong byte count) @ " + tbc); tbc += dssize; // Create the datasegments try { lb.addDataSegment(new I10DataSegment(headerId, dsheader, dsbody)); } catch (MissingI10ParameterException e) { // TODO - Improve this message using the mandatory parameter list from the exception throw new TLVFileException("Error parsing DataSegment body (I10) : Missing one of mandatory parameters."); } catch (ParseI10ParameterException e) { throw new TLVFileException("Error parsing DataSegment body (I10) : Could not parse DataSegmentParameters."); } } else if (headerId.equalsIgnoreCase("I03")) { // total records read byte[] trailertotrecs = new byte[3]; // Have left the loop, means it found the footer byte[] trailerbody = new byte[4]; if (dis.read(trailerbody, 0, 4) != 4) // Trailer Body throw new TLVFileException( "Error reading Trailer Body (I03, wrong byte count) @ " + tbc); tbc += 4; System.arraycopy(trailerbody, 1, trailertotrecs, 0, 3); // TODO - compare the number of records read with the information in the footer dirisegs.add(lb); } else { throw new TLVFileException("Unknown Segment ID found"); } } // dispose all the resources after using them. dis.close(); } catch (FileNotFoundException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } } public Iterator&lt;LogicalBlock&gt; getLogicalBlocks() { return dirisegs.iterator(); } public Iterator&lt;DataSegment&gt; getDataSegments(){ ArrayList&lt;DataSegment&gt; a = new ArrayList&lt;DataSegment&gt;(); Iterator&lt;LogicalBlock&gt; i = getLogicalBlocks(); while (i.hasNext()){ Iterator&lt;DataSegment&gt; j = i.next().getDataSegments(); while (j.hasNext()){ a.add((DataSegment)j.next()); } } return a.iterator(); } } </code></pre> <p>P.S.: I've omitted the other classes as they are pretty much only byte-parsing.</p>

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<pre><code>var studentRepo = new StudentRepository(); int gradeParaleloId = Convert.ToInt32(cmbGradeParalelo.SelectedValue); var students = studentRepo.FindAllStudentsFromGradeParalelo(gradeParaleloId); int year = DateTime.Now.Year; int month = Convert.ToInt32(cmbMes.SelectedIndex) + 1; AttendanceRepository attendanceRepo = new AttendanceRepository(); for (int i = 0; i &lt; students.Count; i++) { for (int j = 1; j &lt; dataGridView1.Columns.Count; j++) { DateTime date = new DateTime(year, month, j); var student = students[i]; var attendance = attendanceRepo.FindAttendance(student.StudentId, date); if (attendance == null) { attendance = new Data.Repositories.Attendance(); attendanceRepo.Add(attendance); } attendance.StudentId = student.StudentId; attendance.DateOfAttendance = date; attendance.Attended = dataGridView1[j, i].Value.ToString(); } } attendanceRepo.SaveChanges(); </code></pre> <p>My main thorn in the side is that for each day in the month, I have to query the database, and see if a record already exists in the DB for that day and student.</p> <p>The upside is that I'm putting each attendance in the datacontext and only pushing the save at the very end as a transaction of sorts. </p> <p>So I'm not inserting on every day for every student. Imagine for a class of 40 students. That's an easy \$40 * 30 = 1200\$ queries on the spot.</p> <p>Is there some way for me to streamline this? I'm more concerned about this line:</p> <pre><code>var attendance = attendanceRepo.FindAttendance(student.StudentId, date); </code></pre>

1890

<p>From <a href="http://mitpress.mit.edu/sicp/full-text/book/book-Z-H-15.html" rel="nofollow">SICP 2.2.4</a>:</p> <p>The textbook has already defined a function (right-split ...) as follows:</p> <blockquote> <pre><code>(define (right-split painter n) (if (= n 0) painter (let ((smaller (right-split painter (- n 1)))) (beside painter (below smaller smaller))))) </code></pre> </blockquote> <p>and they have indicated that there exists a procedure (up-split ...) which has much the same structure.</p> <blockquote> <p>Exercise 2.45. Right-split and up-split can be expressed as instances of a general splitting operation. Define a procedure split with the property that evaluating</p> <pre><code>(define right-split (split beside below)) (define up-split (split below beside)) </code></pre> <p>produces procedures right-split and up-split with the same behaviors as the ones already defined.</p> </blockquote> <p>I wrote the following function, but I'm not sure the best way to test it. What do you think?</p> <pre><code>(define (split step1 step2) (define (split-f painter n) (if (= n 0) painter (let ((smaller (split-f painter (- n 1)))) (step2 (step1 smaller smaller))))) split-f) (define right-split (split beside below)) (define up-split (split below beside)) </code></pre>

1895

<blockquote> <p><strong>Exercise 2.46.</strong></p> <p>A two-dimensional vector v running from the origin to a point can be represented as a pair consisting of an x-coordinate and a y-coordinate. Implement a data abstraction for vectors by giving a constructor make-vect and corresponding selectors xcor-vect and ycor-vect. In terms of your selectors and constructor, implement procedures add-vect, sub-vect, and scale-vect that perform the operations vector addition, vector subtraction, and multiplying a vector by a scalar:</p> <p>$$ (r_1, y_1) + (r_2, y_2) = (r_1 + r_2, y_1 + y_2) \\ (r_1, y_1) - (r_2, y_2) = (r_1 - r_2, y_1 - y_2) \\ s \cdot (r, y) = (sr, sy) $$</p> </blockquote> <p>I wrote the following:</p> <pre><code>(define (make-vect xcor ycor) (cons xcor ycor)) (define xcor-vect car) (define ycor-vect cdr) (define (add-vect v1 v2) (make-vect (+ (xcor-vect v1) (xcor-vect v2)) (+ (ycor-vect v1) (ycor-vect v2)))) (define (sub-vect v1 v2) (make-vect (- (xcor-vect v1) (xcor-vect v2)) (- (ycor-vect v1) (ycor-vect v2)))) (define (scale-vect v1 s) (make-vect (* (xcor-vect v1) s) (* (ycor-vect v1) s))) </code></pre> <p>Can it be improved?</p>

1896

<p>I have a class which is responsible for checking whether a website is up or down. I've made it to run asynchronously, but I would like critique if this is a good/bad way or if there is another better way to do it.</p> <pre><code>class UrlChecker { private readonly IValidationCondition _condition; private readonly Dictionary&lt;string, UrlStatus&gt; _status = new Dictionary&lt;string, UrlStatus&gt;(); private readonly object _lock = new object(); public UrlChecker(IValidationCondition condition) { _condition = condition; } public void CheckRange(IEnumerable&lt;string&gt; urls, Action&lt;Dictionary&lt;string, UrlStatus&gt;&gt; callback) { var options = new ParallelOptions {MaxDegreeOfParallelism = 5}; Parallel.ForEach(urls, options, Check); callback(_status); } private void Check(string url) { Console.WriteLine("Checking " + url); var req = (HttpWebRequest) WebRequest.Create(url); req.Timeout = 10 * 10000; // 10 seconds HttpWebResponse resp; try { resp = (HttpWebResponse)req.GetResponse(); } catch(WebException ex) { // We got an exception, consider it as down lock (_lock) _status.Add(url, UrlStatus.Down); return; } if(resp.StatusCode != HttpStatusCode.OK) { lock (_lock) _status.Add(url, UrlStatus.Down); return; } using(var reader = new StreamReader(resp.GetResponseStream())) { // Check for empty response var html = reader.ReadToEnd(); if(string.IsNullOrEmpty(html)) { lock(_lock) { _status.Add(url, UrlStatus.Down); } } // Validate against condition if(!_condition.IsValid(html)) { lock(_lock) { _status.Add(url, UrlStatus.Down); } return; } } // We reached the end without problems, it's a valid url lock(_lock) { _status.Add(url, UrlStatus.OK); } } } </code></pre> <p>It's called like so:</p> <pre><code>checker.CheckRange(urls, status =&gt; { if(status.Any(x =&gt; x.Value == UrlStatus.Down)) EmailFailing(message); }); </code></pre> <p>The second parameter is obviously a callback that's invoked when all checks are done.</p> <p>Am I locking correctly?</p> <p>Is this an acceptable way of doing it? Checking with Fiddler proves that it's working correctly, but is there a better way?</p>

1903

<p>I have been reviewing the code of a new co-worker and, although in general I think it's OK, there's a thing that causes me mixed feelings:</p> <pre><code> private void Method(...) { Thread t = new Thread(() =&gt; { // Some ~50 lines of code here }); t.Start(); } </code></pre> <p>This is no big deal, but I'm curious about what you guys think of it. Is this exactly what lambdas are for? Or just the opposite? I try to avoid any lambda which doesn't fit on a couple lines at most...</p>

1911

<p>The script is fully working, but I ask is there a better way I can do this rather than name all of the query variables, <code>$q</code>, <code>$q1</code> etc, and then use <code>if</code> <code>else</code> statements to execute the code.</p> <pre><code>&lt;?php // open the mysql connection require_once('mysqli.php'); // successful login variables $q = $dbc -&gt; prepare("SELECT * FROM accounts WHERE email = ? &amp;&amp; password = ? &amp;&amp; logcount != ''"); $q -&gt; bind_param('ss', ($_POST['email']), ($_POST['password'])); $q -&gt; execute(); $q -&gt; store_result(); // wrong password variables $q1 = $dbc -&gt; prepare("SELECT * FROM accounts WHERE email = ? &amp;&amp; password != ? &amp;&amp; logcount != ''"); $q1 -&gt; bind_param('ss', ($_POST['email']), ($_POST['password'])); $q1 -&gt; execute(); $q1 -&gt; store_result(); // not active variables $q2 = $dbc -&gt; prepare("SELECT * FROM accounts WHERE email = ? &amp;&amp; logcount = ''"); $q2 -&gt; bind_param('s', ($_POST['email'])); $q2 -&gt; execute(); $q2 -&gt; store_result(); // successful login query if ($q -&gt; num_rows == 1) { $q = $dbc -&gt; prepare("UPDATE accounts SET logcount = logcount+1 WHERE email = ?"); $q -&gt; bind_param('s', ($_POST['email'])); $q -&gt; execute(); $dbc -&gt; close(); header('location: shack'); exit(); } // wrong password query elseif ($q1 -&gt; num_rows == 1) { echo '&lt;p&gt;Your password is incorrect.&lt;/p&gt;'; } // not activated query elseif ($q2 -&gt; num_rows == 1) { echo '&lt;p&gt;Your account is not activated.&lt;/p&gt;'; } // blank email form entry elseif (empty($_POST['email'])) { echo '&lt;p&gt;You did not fill in an email on the login form.&lt;/p&gt;'; } // account not found else { echo '&lt;p&gt;An account could not be found.&lt;/p&gt;'; } // close the mysql connection $dbc -&gt; close(); ?&gt; </code></pre>

1915

<p>I've been using the following the code to store temporal error messages in <code>TempData</code>, to be displayed from my master page on production sites without any problems, but is this a good way of doing it?</p> <h2>The controller helper code:</h2> <pre><code>namespace System.Web.Mvc { public static class Controllers { public static void SetMessage(this ControllerBase controller, string message) { List&lt;string&gt; messages = controller.TempData["Messages"] as List&lt;string&gt; ?? new List&lt;string&gt;(); messages.Add(message); controller.TempData["Messages"] = messages; } public static void SetErrorMessage(this ControllerBase controller, string errorMessage) { List&lt;string&gt; messages = controller.TempData["ErrorMessages"] as List&lt;string&gt; ?? new List&lt;string&gt;(); messages.Add(errorMessage); controller.TempData["ErrorMessages"] = messages; } } } </code></pre> <h2>Example Use:</h2> <pre><code>public ActionResult Edit() { // .. do stuff this.SetMessage("You edited X."); return View(); } </code></pre> <h2>Here is the rendering code:</h2> <pre><code>&lt;% if (TempData["ErrorMessages"] != null) { %&gt; Error Messages &lt;% foreach (string s in TempData["ErrorMessages"] as List&lt;string&gt;) { %&gt;&lt;%=s%&gt;&lt;% } } if (TempData["Messages"] != null) { %&gt; Messages &lt;% foreach (string s in TempData["Messages"] as List&lt;string&gt;) { %&gt;&lt;%=s%&gt;&lt;% } } %&gt; </code></pre> <p>Can you spot any issues?</p>

1926

<p>I am making a simple transposition cipher. I am testing the program with the word "computer" with the secret key "5,2,8,3,7,1,4,6", where the encrypt method will put the 5th letter 'u' in the first position, 2nd letter 'o' in 2nd position, 8th letter 'r' in 3rd position...</p> <p>So the output would be:<br> original: computer<br> encrypted:uormecpt<br> decrypted:computer </p> <p>Right now my decrypt method is of O(n^2). How can I make this faster?</p> <p>Where char[] y would be uormecpt. The z[j] - 1 is the offset as my iterator starts from 0, but my key starts at 1.</p> <pre><code>public static char[] decrypt(char[] y, int[] z) { char[] decrypted = new char[y.length]; for (int i = 0; i &lt; y.length; i++) { for (int j = 0; j &lt; y.length; j++) { if (i == z[j]-1) decrypted[i] = y[j]; } } return decrypted; } </code></pre>

1927

<p>I have this version comparison function in java. </p> <p>Any cleaner way to write this without all the nested 'if' statements? </p> <p>Note that the suggestions must be in Java code only.</p> <pre><code>@Override public int compareTo(Version o) { int result = this.major.compareTo(o.major); if (result == 0) { result = this.minor.compareTo(o.minor); if (result == 0) { result = this.minor2.compareTo(o.minor2); if (result == 0) { result = this.suffix.compareTo(o.suffix); } } } return result; } </code></pre> <p>Edit: </p> <p>Just to be clear on the 'type' of the fields of the Version class:</p> <pre><code>Integer major, minor, minor2; String suffix; </code></pre>

1934

<p>I am trying to learn how to write good, clean, and efficient JavaScript. I consider myself a novice, at best, in JavaScript. Any comments are appreciated.</p> <p>In an effort to become a better JavaScript programmer, I am trying to write a simple JavaScript animation using HTML5's new canvas element. Functionally speaking, when the canvas is clicked, a new circle (or Ball) is added to the canvas and begins moving to the lower right corner of the canvas. When the ball hits a wall or collides with another ball, the speed at which the x and y coordinates are moving is inverted.</p> <p>Is it a good idea to be modifying the <code>this</code> object? For instance does the following pattern make sense?</p> <pre><code>function Point(I) { this.x = I.x; this.y = I.y; this.z = I.z; return this; } </code></pre> <p>Is there any reason why I shouldn't be sending a object and pulling variables off of the input object? I like the syntax for creation, but are there any problems with this pattern?</p> <pre><code>new Point({ x: 10, y: 30 }); new Point({ x: 50, y: 25 z: 3 }); </code></pre> <p><strong>Full Code</strong></p> <pre><code>&lt;!DOCTYPE html&gt; &lt;html lang="en"&gt; &lt;head&gt; &lt;meta charset="utf-8"&gt; &lt;title&gt;Ball Collision&lt;/title&gt; &lt;script src="js/modernizr-1.7.js"&gt;&lt;/script&gt; &lt;script&gt; window.onload = function () { //"use strict"; // Source: http://www.html5rocks.com/tutorials/canvas/notearsgame/ Number.prototype.clamp = function(min, max) { return Math.min(Math.max(this, min), max); }; if (Modernizr.canvas) { var canvas = document.createElement('canvas'), ctx = canvas.getContext('2d'); canvas.width = 500; canvas.height = 375; canvas.style.border = "3px solid red"; function Point(I) { console.log("Point created"); this.x = I.x; this.y = I.y; this.z = I.z; return this; } function Ball(I) { console.log("Ball created"); var SPEED_LIMIT = 10; this.point = new Point(I.point); this.radius = (I.radius &gt; 10 ? I.radius : 10); this.color = I.color; this.speed = new Point(I.speed); this.collision = false; this.mass = I.mass || 1; this.draw = function() { this.point.x = this.point.x.clamp(0 + this.radius, canvas.width - this.radius); this.point.y = this.point.y.clamp(0 + this.radius, canvas.height - this.radius); ctx.beginPath(); ctx.arc(this.point.x, this.point.y, this.radius, 0, Math.PI*2, false); ctx.closePath(); ctx.fillStyle = this.color; ctx.fill(); }; this.update = function() { this.clear(); if ( this.point.x &lt;= this.radius || this.point.x &gt;= (canvas.width - this.radius)) { this.speed.x *= -1; } if ( this.point.y &lt;= this.radius || this.point.y &gt;= (canvas.height - this.radius)) { this.speed.y *= -1; } if ( this.speed.x &gt; SPEED_LIMIT ) { this.speed.x = SPEED_LIMIT; } if ( this.speed.x &lt; SPEED_LIMIT * -1 ) { this.speed.x = SPEED_LIMIT * -1; } if ( this.speed.y &gt; SPEED_LIMIT ) { this.speed.y = SPEED_LIMIT; } if ( this.speed.y &lt; SPEED_LIMIT * -1 ) { this.speed.y = SPEED_LIMIT * -1; } this.point.x += this.speed.x; this.point.y += this.speed.y; }; this.clear = function() { ctx.beginPath(); ctx.arc(this.point.x - 1, this.point.y - 1, this.radius + 2, 0, Math.PI*2, false); ctx.closePath(); ctx.fillStyle = "#fff"; ctx.fill(); }; return this; } var balls = []; function handleCollisions() { function collide(ball1, ball2) { ball1.speed.x *= -1; ball2.speed.x *= -1; ball1.speed.y *= -1; ball2.speed.y *= -1; } function checkCollisions() { var i, j, a, b; for ( i = 0; i &lt; balls.length; i++ ) { for ( j = i+1; j &lt; balls.length; j++ ) { a = balls[i]; b = balls[j]; var dx = Math.abs(a.point.x - b.point.x); var dy = Math.abs(a.point.y - b.point.y); var d = (dx*dx)+(dy*dy); var r = (a.radius + b.radius) * (a.radius + b.radius); if ( d &lt; r &amp;&amp; ( !a.collision || !b.collision ) ) { a.collision = true; b.collision = true; collide(a, b); } else if ( d &gt; r ) { a.collision = false; b.collision = false; } } } } checkCollisions(); } function update() { balls.forEach(function(ball) { ball.update(); }); handleCollisions(); } function draw() { balls.forEach(function(ball) { ball.draw(); }); } var FPS = 30; var loop = setInterval( function() { update(); draw(); }, 1000/FPS); canvas.onclick = function(e) { var radiusAndMass = Math.floor(Math.random() * 50) + 1; var speed = Math.floor(Math.random() * 10) + 1; balls.push(new Ball({ point: { //x: Math.floor(Math.random() * canvas.width), //y: Math.floor(Math.random() * canvas.height), x: e.offsetX, y: e.offsetY }, color: "#"+((1&lt;&lt;24)*Math.random()|0).toString(16), radius: radiusAndMass, mass: radiusAndMass, speed: { x: speed, y: speed } })); }; document.getElementById('canvas-container').appendChild(canvas); } }; &lt;/script&gt; &lt;/head&gt; &lt;body&gt; &lt;div id="wrap"&gt; &lt;div id="canvas-container"&gt; &lt;/div&gt; &lt;/div&gt; &lt;/body&gt; &lt;/html&gt; </code></pre>

1940

<p>I'm working on interfacing some older positioning equipment with an arduino, but having done the majority of my work with higher level language I'm having trouble adjusting to the limitations of AVR-GCC.</p> <p>I basically have two questions: Is this a good way to parse out the strings? What can I do to optimize this code for an embedded platform?</p> <pre><code>// this is in the global scope of my program. normally accepted as bad code, // but it seems to make sense in the context of an embedded platform. // "global" cache int data[10]; void getPosition(){ // position message is always less than 25 bytes with null termination characters byte bufferIndex = 0; char buffer[25]; // read the position command from the serial port // should look like: // D20BIX+00733Y+00080S99\r\n // // and we need the X+00000 and Y+00000 parts // if (Serial.available() &gt; 0){ while (Serial.available() &gt; 0 &amp;&amp; bufferIndex &lt; 25){ buffer[bufferIndex] = Serial.read(); if (buffer[bufferIndex++] == '\n'){ buffer[bufferIndex] = '\0'; break; } } Serial.flush(); // check to see if we have good orientation on the buffer by // checking for lines starting with model identifier 'D' String input = String(buffer); if (buffer[0] == 'D' &amp;&amp; bufferIndex &lt;=24){ int x_result = data[1]; int y_result = data[4]; String check; char token_buffer[8] = {'0', '0', '0', '0', '0', '0', '0', '0' }; // scan for x, target token is X+00000 String x_token = input.substring(5, 11); check = x_token.substring(2, 6); check.toCharArray(token_buffer, 8); x_result = atoi(token_buffer); if (x_token[1] == '-'){ x_result *= -1; } // scan for y, target token is Y+00000 String y_token = input.substring(12, 18); check = y_token.substring(2, 6); check.toCharArray(token_buffer, 8); y_result = atoi(token_buffer); if (y_token[1] == '-'){ y_result *= -1; } // finalize results data[1] = x_result; data[4] = y_result; } } } </code></pre>

1942

<p>I have a form that submits to a servlet that has optional parameters. If they are empty they are just ignored. This is the template I am using:</p> <pre><code>if (!(param = (String)params.get("httpParam")).equals("")) { // Handle parameter } </code></pre> <p>It doesn't quite feel right. It <em>works</em>, but I think it could be more readable. Any suggestions?</p>

1947

<p>I have decided to go PDO and have started implementing it on one of my webprojects. I have limited programing skills but can usually pull it off with some tutorials and forums.</p> <p>Here is my code this far and it works fine but how is the code correct regarding the picking up errors, syntax, order and begintransaction etc.? Have I missunderstood anything? Is anything unneccesary?</p> <p>connect.php</p> <pre><code> &lt;?php try { $DBH = new PDO("mysql:host=$host;dbname=$database", $username, $password, array( PDO::ATTR_PERSISTENT =&gt; true )); $DBH -&gt; exec("set names utf8"); } catch(PDOException $e) { echo $e-&gt;getMessage(); } ?&gt; </code></pre> <p>query.php</p> <pre><code>try { $DBH-&gt;setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION); $DBH-&gt;beginTransaction(); $STH = $DBH-&gt;prepare('SELECT id from users where uid = :uid'); $STH-&gt;setFetchMode(PDO::FETCH_ASSOC); $STH-&gt;bindParam(':uid', $uid); // $uid value is set $STH-&gt;execute(); $uid_in_db = $STH-&gt;rowCount(); if($uid_in_db==0){ //=new user, insert info in db. $STH = $DBH-&gt;prepare("INSERT INTO USERS (uid,namn) VALUES (:uid, :name)"); $STH-&gt;bindParam(':uid', $uid); $STH-&gt;bindParam(':namn', $_POST['namn']); // a value posted form user input $STH-&gt;execute(); } $DBH-&gt;commit(); // } catch (Exception $e) { $DBH-&gt;rollBack(); echo "Fel: " . $e-&gt;getMessage(); } }else{ $error=1; } </code></pre>

1949

<p>I just wrote this small inch &lt;-> cm conversion program. It works just fine, although I know that I've done some things in a rather stupid manner and that it could be improved.</p> <pre><code>def conversion(): try: amount = int(raw_input("Please enter the value: ")) except ValueError: print "Please specify a valid amount." return conversion() answer = raw_input("Please choose between converting FROM kilograms/pounds: ") if answer == "kilograms": return amount * 2.2 elif answer == "pounds": return amount / 1.45 else: print "Please choose between kilograms and pounds." restart = raw_input("Try again? ") if restart == "yes": return conversion() elif restart == "y": return conversion() else: print "Okay, bye." return print conversion() </code></pre>

1952

<p>Below I have some jQuery code that handles footnotes. My question is actually about the formatting and indentation of the code, so I won't bother trying to explain what the code does beyond that.</p> <p>I'd like to know what patterns of indentation are considered the most maintainable and readable when chaining jQuery function calls of the form: <code>$(foo).foo(bar).foo(function(){ bar; }).foo(function(){ bar; });</code></p> <p>Here is my specific code and the formatting/indentation that I've come up with:</p> <pre><code>$('.footnote[id^="ret_"]') .removeAttr('title') .removeAttr('alt') .mouseenter(function(e) { var footnote = $('#footnote_cont_' + this.id.substring(4)).html(); $footnoteTooltip.stop(true, false); //only completely hide and change text/position if we are hovering over a different footnote if($footnoteTooltip.html() != footnote) $footnoteTooltip.hide().html(footnote).css({ left: e.pageX + 10, top: e.pageY + 15}); $footnoteTooltip.fadeTo(fadeTime, opacity); }) .mouseleave(function() { $footnoteTooltip.delay(fadeTime).fadeOut(fadeTime); }) ; </code></pre> <p>Is there a more readable way of indenting this?</p>

1957

<p>I need to get the total milliseconds to the next mid-day (12:00:00) to signal a timer that will run once a day. </p> <p>Assuming the application can be shut down and started anytime, is this code to get the milliseconds left to midday (used to set the timer) correct? (It doesn't need to be exact; it can be off by a few seconds.)</p> <pre><code>TimeSpan now = DateTime.Now.TimeOfDay; TimeSpan target = new DateTime(DateTime.Now.Year, DateTime.Now.Month, DateTime.Now.Day, 12, 0, 0).TimeOfDay; double r = target.TotalMilliseconds - now.TotalMilliseconds; if (r &gt; 0) // It's before noon ; else // It's after noon r = TimeSpan.FromTicks(TimeSpan.TicksPerDay).TotalMilliseconds + r; t = new Timer(DoWork, null, r, TimeSpan.FromTicks(TimeSpan.TicksPerDay)); </code></pre> <p>Can it be done more efficiently or in fewer lines of code?</p>

1959

<p><a href="http://www.djangoproject.com/" rel="nofollow">Django</a>, "the web framework for perfectionists with deadlines", is a Python-based framework for creating web applications.</p> <p>With a powerful object-based database mapper, a clean syntax for mapping URLs to views, a simple template language and a convenient automatically generated administration interface, Django is one of the most popular of the Python web frameworks. </p> <p>Django focuses on automating as much as possible while adhering to the <a href="http://c2.com/cgi/wiki?DontRepeatYourself" rel="nofollow">DRY principle</a>. It lets you build high-performing, elegant Web applications quickly.</p>

1965

Django is a Python-based framework for creating web applications.

1966

<p>I want to join strings together, but when doing this it often happens that there is a comma too many, and therefore I need to remove that comma. In this code, I use the <code>substring</code> to delete the two last characters.</p> <p>How can this become more elegant?</p> <pre><code>List&lt;String&gt; paramList = new ArrayList&lt;String&gt;( ); paramList.add( "param1" ); paramList.add( "param2" ); StringBuilder result = new StringBuilder(); for ( String p : paramList ) { result.append( p ).append( ", " ); } String withoutLastComma = result.substring( 0, result.length( ) - ", ".length( ) ); System.err.println( withoutLastComma ); </code></pre>

1973

<p>Could someone review an <a href="https://stackoverflow.com/questions/5644093/returning-first-result-where-case-result-x/5680184#5680184">accepted answered</a> I gave on Stack Overflow?</p> <p>The use-case is as follows:</p> <blockquote> <p>Given a messaging system where a user can receive a message from a single user and send messages to one or more users, return the most recent communication (sent or received) between a passed userId and the individual(s) that user communicated with.</p> </blockquote> <p>For the example, I have three tables:</p> <p><strong>Users</strong></p> <blockquote> <pre class="lang-none prettyprint-override"><code>id user_name 1 Walker 2 John 3 Kate </code></pre> </blockquote> <p><strong>Messages</strong></p> <blockquote> <pre class="lang-none prettyprint-override"><code>id senderid body time 1 1 ignored 1 2010-04-01 00:00:00.000 2 1 ignored 2 2010-04-02 00:00:00.000 3 3 ignored 3 2010-04-03 00:00:00.000 4 1 msg A to john and kate 2010-04-10 00:00:00.000 5 3 msg b from kate to walker and john 2010-04-11 00:00:00.000 </code></pre> </blockquote> <p><strong><code>messages_recipients</code></strong></p> <blockquote> <pre class="lang-none prettyprint-override"><code>id messageid userid 1 1 2 2 1 3 3 2 2 4 3 1 5 4 2 6 4 3 7 5 1 8 5 2 </code></pre> </blockquote> <p>The data is tailored in such a way that I want a list of communications between user Walker and the people Walker has spoken with. </p> <p>You can see a list of these messages by running the following SQL statement:</p> <pre class="lang-sql prettyprint-override"><code>SELECT u2.user_name AS Sender, u1.user_name AS Receiver, m.body, m.time FROM messages m JOIN messages_recipients mr ON m.id = mr.messageid JOIN users u1 ON mr.userid = u1.id JOIN users u2 ON m.senderid = u2.id ORDER BY time DESC </code></pre> <p>Now that we have the test scenario, the part I want reviewed: returning the most recently communicated message between Walker, John, and Kate.</p> <pre class="lang-sql prettyprint-override"><code>BEGIN DECLARE @UserId INT = 1 --A. Main Query SELECT CASE WHEN mtemp.senderid = 1 --@UserId THEN CONCAT('Message To: ', receivers.user_name) ELSE CONCAT('Message From: ' , senders.user_name) END AS MessageType, mtemp.body, mtemp.time FROM messages mtemp INNER JOIN users senders ON mtemp.senderid = senders.id INNER JOIN ( --B. Inner Query determining most recent message (based on time) -- between @UserID and the person @UserID -- Communicated with (either as sender or receiver) select userid,max(maxtime) as maxmaxtime from ( --C.1. First part of Union Query Aggregating sent/received messages on passed @UserId SELECT m2.body, kk.* FROM `messages` m2 INNER JOIN ( SELECT DISTINCT userid, MAX(m.time) AS MaxTime FROM messages m INNER JOIN messages_recipients mr ON m.id = mr.messageid AND m.senderid = 1 --@UserId GROUP BY mr.userid ) kk on m2.time = kk.MaxTime and m2.senderid = 1 --@UserId UNION --C.2. Second part of Union Query Aggregating sent/received messages on passed @UserId SELECT m1.body, jj.* FROM `messages` m1 INNER JOIN ----C.2a. Inner most query of users users who sent message to userid (SELECT DISTINCT senderid as userid, MAX(m.time) AS MaxTime FROM messages m INNER JOIN messages_recipients mr ON m.id = mr.messageid AND mr.userid = 1 --@UserId GROUP BY m.senderid) jj on m1.time = jj.MaxTime and m1.senderid = jj.userid ) MaximumUserTime group by MaximumUserTime.userid ) AggregatedData on mtemp.time = AggregatedData.maxmaxtime INNER JOIN users receivers on AggregatedData.userid = receivers.id ORDER BY `time` DESC END </code></pre> <p>To test in <code>phpMyAdmin</code>, you'll have to remove the comments and the <code>BEGIN</code>/<code>END</code> <code>DECLARE</code> statements as well. I just wanted to post this as if it would look in a procedure.</p> <p>When I run this query I get the following results:</p> <blockquote> <pre class="lang-none prettyprint-override"><code>MessageType body time Message From: Kate msg b from kate to walker and john 2010-04-11 00:00:00.000 Message To: John msg A to john and kate 2010-04-10 00:00:00.000 </code></pre> </blockquote> <p>That's the most recent communications concerning Walker among all those users who have communicated with Walker.</p> <p>Is there a better way to run this query?</p>

1981

<p>I needed to write code in WPF for a client. The application is done with prism (not my decision, they already had people working on it), so I got a sparkling clean new module to work in. Since this was my first time writing WPF code going to production, I wanted to handle the code in a good manner. I decided to go MVVM.</p> <p>I structured the module as follows (I do need to move the <code>RelayCommand</code> and <code>ViewModelBase</code>):</p> <ul> <li>Services (<code>IItemTypeService.cs</code>, <code>ItemTypeService.cs</code>)</li> <li>ViewModels (<code>ItemTypeViewModel.cs</code>, <code>ItemTypeViewModel.cs</code>, <code>RelayCommand.cs</code>, <code>ViewModelBase.cs</code>)</li> <li>Views (<code>ItemTypeAdminView.xaml</code>, <code>ItemTypeDetailView.xaml</code>)</li> </ul> <p>The <code>ViewModelBase</code> implements <code>INotifyPropertyChanged</code>.</p> <p>The <code>ItemTypeAdminView</code> is the main view. <code>ItemTypeDetailView</code> is a user control and is put into the <code>ItemTypeAdminView</code>. The <code>ItemTypeAdminView</code> will in the future be expanded with other sections, and those sections will use the same information as the <code>ItemTypeDetailView</code>.</p> <p>Therefore, I made a <code>ViewModel</code> for the <code>ItemTypeAdminView</code>, not for the <code>ItemTypeDetailView</code>. Every <code>ItemType</code> is coming from Linq2SQL (yes, I know about EF - I wasn't involved in this part), and is wrapped in a <code>ItemTypeViewModel</code> so it can implement the <code>INotifyPropertyChanged</code>.</p> <p>The code for the <code>ItemTypeAdminViewModel</code>:</p> <pre><code>public class ItemTypeAdminViewModel : ViewModelBase { #region private fields private ICollectionView collectionView; private IItemTypeService itemTypeService; #endregion #region automatic properties public ObservableCollection&lt;ItemTypeViewModel&gt; ItemTypes { get; private set; } public IEnumerable&lt;Company&gt; Companies { get; private set; } public IEnumerable&lt;CompanyGTIN&gt; CompanyGTINs { get; private set; } private Company selectedCompany; public Company SelectedCompany { get { return selectedCompany; } set { selectedCompany = value; LoadCompanyGTINs(); } } #endregion properties #region constructors public ItemTypeAdminViewModel(IItemTypeService itemTypeService) { this.itemTypeService = itemTypeService; Initialize(); } #endregion #region private methods private void Initialize() { //Should I wrap in Try/Catch? Try/Catch is expensive, must find something else... ItemTypes = new ObservableCollection&lt;ItemTypeViewModel&gt;(itemTypeService.GetItemTypes()); Companies = itemTypeService.GetCompanies(); collectionView = CollectionViewSource.GetDefaultView(ItemTypes); } private void LoadCompanyGTINs() { CompanyGTINs = itemTypeService.GetCompanyGTINs(selectedCompany.ID); OnPropertyChanged("CompanyGTINs"); } #endregion #region commands public ICommand GoToFirstItemType { get { return new RelayCommand(() =&gt; collectionView.MoveCurrentToFirst(), () =&gt; collectionView.CurrentPosition &gt;= 1); } } public ICommand GoToLastItemType { get { return new RelayCommand(() =&gt; collectionView.MoveCurrentToLast(), () =&gt; collectionView.CurrentPosition &lt; (ItemTypes.Count - 1)); } } public ICommand NextItemType { get { LoadCompanyGTINs(); return new RelayCommand(() =&gt; collectionView.MoveCurrentToNext(), () =&gt; collectionView.CurrentPosition &lt; (ItemTypes.Count - 1)); } } public ICommand PreviousItemType { get { return new RelayCommand(() =&gt; collectionView.MoveCurrentToPrevious(), () =&gt; collectionView.CurrentPosition &gt;= 1); } } #endregion } </code></pre> <p>And the code for the <code>ItemTypeDetailView</code> XAML:</p> <pre><code>&lt;Grid&gt; &lt;Grid.RowDefinitions&gt; &lt;RowDefinition Height="Auto" /&gt; &lt;RowDefinition Height="Auto" /&gt; &lt;RowDefinition Height="*" /&gt; &lt;RowDefinition Height="Auto" /&gt; &lt;/Grid.RowDefinitions&gt; &lt;Grid DataContext="{Binding ItemTypes}"&gt; &lt;Grid.ColumnDefinitions&gt; &lt;ColumnDefinition /&gt; &lt;ColumnDefinition /&gt; &lt;/Grid.ColumnDefinitions&gt; &lt;Grid.RowDefinitions&gt; &lt;RowDefinition Height="Auto" /&gt; &lt;RowDefinition Height="Auto" /&gt; &lt;RowDefinition Height="Auto" /&gt; &lt;RowDefinition Height="Auto" /&gt; &lt;RowDefinition Height="Auto" /&gt; &lt;RowDefinition Height="Auto" /&gt; &lt;RowDefinition Height="Auto" /&gt; &lt;RowDefinition Height="Auto" /&gt; &lt;RowDefinition Height="Auto" /&gt; &lt;RowDefinition Height="Auto" /&gt; &lt;RowDefinition Height="Auto" /&gt; &lt;RowDefinition Height="Auto" /&gt; &lt;RowDefinition Height="Auto" /&gt; &lt;RowDefinition Height="Auto" /&gt; &lt;/Grid.RowDefinitions&gt; &lt;TextBlock Text="Name:" /&gt; &lt;TextBox Grid.Column="2" Text="{Binding Name}" /&gt; &lt;TextBlock Grid.Row="1" Text="Description:" /&gt; &lt;TextBox Grid.Column="1" Grid.Row="1" Text="{Binding Description}" /&gt; &lt;TextBlock Grid.Row="2" Text="Manufacturer:" /&gt; &lt;ComboBox Grid.Column="1" Grid.Row="2" DisplayMemberPath="Name" ItemsSource="{Binding Path=DataContext.Companies, RelativeSource={RelativeSource FindAncestor, AncestorType=UserControl, AncestorLevel=2}}" Name="ManufacturerComboBox" SelectedItem="{Binding Mode=TwoWay, Path=DataContext.SelectedCompany, RelativeSource={RelativeSource FindAncestor, AncestorType=UserControl, AncestorLevel=2}}" SelectedValue="{Binding ManufacturerID}" SelectedValuePath="ID" /&gt; &lt;TextBlock Grid.Row="10" Text="Manufacturer Product Code:"/&gt; &lt;TextBox Grid.Column="1" Grid.Row="10" Text="{Binding ManufacturerProductCode}" /&gt; &lt;TextBlock Grid.Row="11" Text="Manufacturer Product GS1 Code:"/&gt; &lt;TextBox Grid.Column="1" Grid.Row="11" Text="{Binding ManufacturerProductGS1Code}" /&gt; &lt;TextBlock Grid.Row="12" Text="GS1GTINID:"/&gt; &lt;ComboBox DisplayMemberPath="GTIN" Grid.Column="1" Grid.Row="12" IsSynchronizedWithCurrentItem="True" ItemsSource="{Binding Path=DataContext.CompanyGTINs, RelativeSource={RelativeSource FindAncestor, AncestorType=UserControl, AncestorLevel=2}}" SelectedValue="{Binding GS1GTINID}" SelectedValuePath="ID" /&gt; &lt;/Grid&gt; &lt;Grid Grid.Row="2"&gt; &lt;StackPanel Grid.Row="4" Orientation="Horizontal"&gt; &lt;Button Command="{Binding GoToFirstItemType}"&gt;&amp;lt;&amp;lt;&lt;/Button&gt; &lt;TextBlock Margin="5,0,5,0" /&gt; &lt;Button Command="{Binding PreviousItemType}"&gt;&amp;lt;&lt;/Button&gt; &lt;TextBlock Margin="5,0,5,0" /&gt; &lt;Button Command="{Binding NextItemType}"&gt;&amp;gt;&lt;/Button&gt; &lt;TextBlock Margin="5,0,5,0" /&gt; &lt;Button Command="{Binding GoToLastItemType}"&gt;&amp;gt;&amp;gt;&lt;/Button&gt; &lt;TextBlock Margin="5,0,5,0" /&gt; &lt;Button Command="{Binding New}"&gt;New&lt;/Button&gt; &lt;/StackPanel&gt; &lt;/Grid&gt; &lt;/Grid&gt; </code></pre> <p>I am really curious about what could be improved structure/code wise and/or what should be left out.</p>

1983

<p><a href="http://www.ruby-lang.org/" rel="nofollow">Ruby</a> is an open-source, dynamic, object-oriented, interpreted language that combines the good bits from Perl, Smalltalk, and Lisp. Its primary purpose is to "help every programmer in the world to be productive, and to enjoy programming, and to be happy." Ruby focuses on simplicity and productivity.</p> <p>Ruby was initially conceived on February 24, 1993 by <a href="http://en.wikipedia.org/wiki/Yukihiro_Matsumoto" rel="nofollow">Yukihiro Matsumoto</a> ('Matz'), and version 1.0 was released in 1996. The current stable version is <a href="http://en.wikipedia.org/wiki/Ruby_%28programming_language%29#Ruby_2.2" rel="nofollow">2.2.2</a>.</p> <p>Ruby's mindshare spiked around 2005 due to Ruby on Rails, an MVC (Model, View, Controller) framework for building web applications, and usage continues to grow as of 2013 with Ruby continuing to find acceptance in the commercial marketplace.</p> <p>Ruby supports multiple programming paradigms, including functional, object oriented and imperative. It also has a dynamic type system and automatic memory management; it is therefore similar in varying respects to Smalltalk, Python, Perl, Lisp, Dylan, and CLU.</p> <p>You can download the Ruby source code from <a href="http://www.ruby-lang.org/en/downloads/" rel="nofollow">ruby-lang.org</a> or from <a href="https://github.com/ruby/ruby" rel="nofollow">GitHub</a>.</p> <h2>Naming Conventions^{<a href="http://rubylearning.com/satishtalim/ruby_names.html" rel="nofollow">1</a>}</h2> <p><strong>Ruby Names</strong> are used to refer to constants, variables, methods, classes, and modules. <em>The first character of a name helps Ruby to distinguish its intended use.</em> Certain names are reserved words and should not be used as variable, method, class, or module name. Lowercase letter means the characters "a" through "z". Uppercase letter means "A" through "Z", and digit means "0" through "9". A name is an uppercase letter, lowercase letter, or an underscore ("_"), followed by <strong><em>Name characters</em></strong> (this is any combination of upper- and lowercase letters, underscore and digits).</p> <p><strong>Variables</strong></p> <p>Variables in Ruby can contain data of any type. You can use variables in your Ruby programs <em>without any declarations</em>. Variable name itself denotes its scope (local, global, instance, etc.).</p> <ul> <li>A <strong>local</strong> variable (declared within an object) name consists of a lowercase letter (or an underscore) followed by name characters (<code>sunil</code>, <code>_z</code>, <code>hit_and_run</code>).</li> <li>An <strong>instance</strong> variable (declared within an object always "belongs to" whatever object <strong>self</strong> refers to) name starts with an "at" sign (<code>@</code>) followed by a <em>name</em> (<code>@sign</code>, <code>@_</code>, <code>@Counter</code>).</li> <li>A <strong>class</strong> variable (declared within a class) name starts with two "at" signs (<code>@@</code>) followed by a <em>name</em> (<code>@@sign</code>, <code>@@_</code>, <code>@@Counter</code>). A class variable is shared among all objects of a class. Only one copy of a particular class variable exists for a given class. Class variables used at the top level are defined in <strong>Object</strong> and behave like global variables. <em>Class variables are rarely used in Ruby programs</em>.</li> <li><strong>Global</strong> variables start with a dollar sign (<code>$</code>) followed by name characters. A global variable name can be formed using <code>$-</code> followed by any single character (<code>$counter</code>, <code>$COUNTER</code>, <code>$-x</code>). Ruby defines a number of global variables that include other punctuation characters, such as <code>$_</code> and <code>$-K</code>.</li> </ul> <p><strong>Constants</strong></p> <p>A <strong>constant</strong> name starts with an uppercase letter followed by name characters. Class names and module names are constants, and follow the constant naming conventions. Examples: <code>module MyMath</code>, <code>PI=3.1416</code>, <code>class MyPune</code>.</p> <p><strong>Method Names</strong></p> <p><strong>Method</strong> names should begin with a lowercase letter (or an underscore). <code>?</code>, <code>!</code> and <code>=</code> are the only weird characters allowed as method name suffixes (<code>!</code> or <strong>bang</strong> labels a method as dangerous - specifically, as the dangerous equivalent of a method with the same name but without the bang)</p> <p>Knowledge Base:</p> <ul> <li><a href="http://apidock.com/ruby" rel="nofollow">API (APIdock)</a></li> <li><a href="http://tryruby.org/" rel="nofollow">Try Ruby</a></li> </ul>

1986

Ruby is a multi-platform, open-source, dynamic, object-oriented, interpreted language created by Yukihiro Matsumoto (Matz) in 1993.

1987

<p><strong>Ruby on Rails</strong> is an open-source web framework that's optimized for programmer happiness and sustainable productivity. It lets you write beautiful code by favouring convention over configuration.</p> <ul> <li><a href="http://rubyonrails.org/" rel="nofollow">Ruby on Rails website</a></li> <li><a href="http://weblog.rubyonrails.org/" rel="nofollow">Riding Rails official blog</a></li> <li><a href="http://api.rubyonrails.org/" rel="nofollow">API documentation</a></li> <li><a href="http://apidock.com/" rel="nofollow">Collaborative API documentation</a></li> <li><a href="http://railsapi.com/" rel="nofollow">Rails Searchable API Doc</a></li> <li><a href="http://guides.rubyonrails.org/" rel="nofollow">Rails Guides</a></li> <li><a href="http://screencasts.com/" rel="nofollow">Rails Screencasts</a></li> <li><a href="http://github.com/rails/rails/" rel="nofollow">Rails Source Code</a></li> <li><a href="https://rails.lighthouseapp.com/projects/8994-ruby-on-rails" rel="nofollow">Rails Lighthouse Issue Tracker</a></li> </ul>

1988

Ruby on Rails is an open-source web development framework written in Ruby. If your question code is written in Ruby on Rails, tag with Ruby as the language tag. Many things are defined by convention, freeing you from having to re-invent things to stay productive.

1989

<p><a href="https://www.python.org/" rel="nofollow noreferrer">Python</a> is a <a href="https://wiki.python.org/moin/Why%20is%20Python%20a%20dynamic%20language%20and%20also%20a%20strongly%20typed%20language" rel="nofollow noreferrer">dynamic and strongly typed</a> programming language that is used for <a href="https://python.org/about/apps" rel="nofollow noreferrer">a wide range of applications</a>. It is a general-purpose, high-level programming language that is designed to emphasize usability.</p> <p>Python allows programmers to express concepts in fewer lines of code than would be possible in languages such as <a href="/questions/tagged/c" class="post-tag" title="show questions tagged &#39;c&#39;" rel="tag">c</a>, and the language has constructs intended to be used to create clear programs in a variety of domains.</p> <p>Two similar but incompatible major versions of Python are in widespread use: 2.7 is supported <a href="https://www.python.org/dev/peps/pep-0373/#id2" rel="nofollow noreferrer">until 2020</a> to run old scripts and dependencies, and version 3 first came out in 2008. Please mention the version and implementation that you are using when asking a question about Python.</p> <p>Python supports multiple programming paradigms, including object-oriented, imperative, and functional programming styles. It features a fully dynamic type system and automatic memory management, similar to that of <a href="/questions/tagged/scheme" class="post-tag" title="show questions tagged &#39;scheme&#39;" rel="tag">scheme</a>, <a href="/questions/tagged/ruby" class="post-tag" title="show questions tagged &#39;ruby&#39;" rel="tag">ruby</a>, <a href="/questions/tagged/perl" class="post-tag" title="show questions tagged &#39;perl&#39;" rel="tag">perl</a> and <a href="/questions/tagged/tcl" class="post-tag" title="show questions tagged &#39;tcl&#39;" rel="tag">tcl</a>.</p> <p>Like other <a href="https://en.wikipedia.org/wiki/Dynamic_programming_language" rel="nofollow noreferrer">dynamic languages</a>, Python is often used as a scripting language, but is also used in a wide range of non-scripting contexts. Using third-party tools, Python code can be packaged into standalone executable programs. Python interpreters are available for many operating systems.</p> <p>CPython, the reference implementation of Python, is free and open source software and has a community-based development model, as do nearly all of its alternative implementations. There are a wide variety of implementations more suited for specific environments or tasks.</p> <p>The philosophy of Python is succinctly formulated in <a href="https://python.org/dev/peps/pep-0020" rel="nofollow noreferrer"><em>The Zen of Python</em></a> written by Tim Peters, which can be revealed by issuing this command at the interactive interpreter:</p> <pre><code>&gt;&gt;&gt; import this </code></pre> <p>The documentation can also be accessed offline for your installation of Python in the following manner:</p> <ol> <li>Going into <code>Your_Python_install_dir/Doc</code>. There is a complete Python documentation present for the version of Python installed on your computer.</li> <li>Running <code>pydoc x</code> or <code>python -m pydoc x</code> from the command prompt or terminal displays documentation for module <code>x</code>.</li> </ol> <p>Unlike many other languages Python uses an indentation based syntax and this may take some getting used to for programmers familiar with braces for syntax.</p> <pre><code>&gt;&gt;&gt; from __future__ import braces File "&lt;stdin&gt;", line 1 SyntaxError: not a chance </code></pre> <p>To help with the transition, it is recommended to use a properly configured text editor created for programmers or an IDE. Python comes with a basic IDE called <a href="https://docs.python.org/2/library/idle.html" rel="nofollow noreferrer">IDLE</a> to get you started. Other popular examples are the charity-ware Vim, the free GNU <a href="/questions/tagged/emacs" class="post-tag" title="show questions tagged &#39;emacs&#39;" rel="tag">emacs</a> and <a href="/questions/tagged/eclipse" class="post-tag" title="show questions tagged &#39;eclipse&#39;" rel="tag">eclipse</a>+PyDev. Take a look at this <a href="https://en.wikipedia.org/wiki/List_of_integrated_development_environments_for_Python#Python" rel="nofollow noreferrer">IDE comparison list</a> for many other alternatives.</p> <hr> <h2>Tagging recommendation:</h2> <p>Use the <a href="/questions/tagged/python" class="post-tag" title="show questions tagged &#39;python&#39;" rel="tag">python</a> tag for all Python related questions. If you believe your question may be even more specific, you can include a version specific tag such as <a href="/questions/tagged/python-3.x" class="post-tag" title="show questions tagged &#39;python-3.x&#39;" rel="tag">python-3.x</a>.</p> <hr> <h2>References</h2> <ul> <li>Official documentation for the current stable versions: <a href="https://docs.python.org/2.7/" rel="nofollow noreferrer">2.7</a> and <a href="https://docs.python.org/3/" rel="nofollow noreferrer">3</a>.</li> <li><a href="https://en.wikipedia.org/wiki/Python_%28programming_language%29" rel="nofollow noreferrer">Python (programming language)</a> (Wikipedia)</li> <li><a href="https://wiki.python.org/moin/BeginnersGuide/Programmers" rel="nofollow noreferrer">Python for Programmers</a></li> <li><a href="http://www.tutorialspoint.com/python/python_quick_guide.htm" rel="nofollow noreferrer">Python - Quick Guide</a></li> <li><a href="https://docs.python.org/3/howto/pyporting.html" rel="nofollow noreferrer">Porting Python 2 Code to Python 3</a></li> <li>The non-profit <a href="https://www.python.org/psf/" rel="nofollow noreferrer">Python Software Foundation</a> manages <a href="https://en.wikipedia.org/wiki/CPython" rel="nofollow noreferrer">CPython</a>.</li> <li><a href="https://www.python.org/psf/" rel="nofollow noreferrer">PSF</a> License Agreement for Python <a href="https://docs.python.org/2.7/license.html" rel="nofollow noreferrer">2.7</a> and <a href="https://docs.python.org/3/license.html" rel="nofollow noreferrer">3</a></li> </ul> <hr> <h2>Popular <a href="https://wiki.python.org/moin/WebFrameworks" rel="nofollow noreferrer">web frameworks</a> based on Python</h2> <ul> <li><p><a href="https://www.djangoproject.com" rel="nofollow noreferrer"><strong>Django</strong></a></p> <p>The Web framework for perfectionists (with deadlines). Django makes it easier to build better Web apps more quickly and with less code. Django is a high-level Python Web framework that encourages rapid development and clean, pragmatic design. It lets you build high-performing, elegant Web applications quickly. Django focuses on automating as much as possible and adhering to the DRY (Don't Repeat Yourself) principle.</p></li> <li><p><a href="http://flask.pocoo.org" rel="nofollow noreferrer"><strong>Flask</strong></a></p> <p>Flask is a micro-framework for Python based on Werkzeug, Jinja 2, and good intentions.</p></li> <li><p><a href="http://www.cherrypy.org" rel="nofollow noreferrer"><strong>CherryPy</strong></a></p> <p>CherryPy is a pythonic, object-oriented web framework that enables developers to build web applications in much the same way they would build any other object-oriented Python program. This results in smaller source code developed in less time. CherryPy has been in use for over 7 years, and it is being used in production by many sites, from the simplest to the most demanding.</p></li> <li><p><a href="http://www.pylonsproject.org/projects/pyramid/about" rel="nofollow noreferrer"><strong>Pyramid</strong></a></p> <p>A lightweight Web framework emphasizing flexibility and rapid development. It combines the very best ideas from the worlds of Ruby, Python and Perl, providing a structured but extremely flexible Python web framework. It is also one of the first projects to leverage the emerging WSGI standard, which allows extensive re-use and flexibility, but only if you need it.</p></li> <li><p><a href="http://webpy.org" rel="nofollow noreferrer"><strong>web.py</strong></a></p> <p>web.py is a web framework for Python that is as simple as it is powerful. web.py is in the public domain; you can use it for whatever purpose with absolutely no restrictions. web.py lets you write web apps in Python.</p></li> <li><p><a href="http://grok.zope.org" rel="nofollow noreferrer"><strong>Grok</strong></a></p> <p>Grok is built on the existing Zope 3 libraries, but aims to provide an easier learning curve and a more agile development experience. It does this by placing an emphasis on convention over configuration and DRY (Don't Repeat Yourself).</p></li> </ul> <h2>Popular Mathematical/Scientific computing libraries in Python</h2> <ul> <li><p><a href="http://www.numpy.org" rel="nofollow noreferrer"><strong>NumPy</strong></a></p> <p>NumPy is the fundamental package for scientific computing with Python. It contains among other things:</p> <ul> <li>a powerful N-dimensional array object</li> <li>sophisticated (broadcasting) functions</li> <li>tools for integrating C/C++ and Fortran code</li> <li>useful linear algebra, Fourier transform, and random number capabilities</li> </ul> <p>These features also make it possible to use NumPy in general-purpose database applications.</p></li> <li><p><a href="http://scipy.org" rel="nofollow noreferrer"><strong>SciPy</strong></a></p> <p>SciPy is an open source library for the Python programming language consisting of mathematical algorithms and functions often used in science and engineering. SciPy includes algorithms and tools for tasks such as optimization, clustering, discrete Fourier transforms, linear algebra, signal processing and multi-dimensional image processing. SciPy is closely related to NumPy and depends on many NumPy functions, including a multidimensional array that is used as the basic data structure in SciPy.</p></li> <li><p><a href="http://matplotlib.org/" rel="nofollow noreferrer"><strong>matplotlib</strong></a></p> <p>matplotlib is a plotting library for the Python programming language and its NumPy numerical mathematics extension. It provides an object-oriented API for embedding plots into applications using general-purpose GUI toolkits like wxPython, Qt, or GTK. There is also a procedural "pylab" interface based on a state machine (like OpenGL) designed to closely resemble that of MATLAB.</p></li> <li><p><a href="http://pandas.pydata.org/" rel="nofollow noreferrer"><strong>pandas</strong></a></p> <p>pandas, the Python Data Analysis Library, is an open source, BSD-licensed library providing high-performance, easy-to-use data structures and data analysis tools for the Python programming language.</p></li> </ul> <hr> <h3>Other Sites</h3> <ul> <li><a href="http://python.org/community/lists/#tutor" rel="nofollow noreferrer">Tutor mailing list</a></li> <li><a href="http://python.org/community/lists/#python-help" rel="nofollow noreferrer">python-help mailing list</a></li> <li><a href="http://www.pycon.org" rel="nofollow noreferrer">PyCon</a></li> <li><a href="http://www.pythonweekly.com" rel="nofollow noreferrer">Python Weekly</a></li> <li><a href="http://pycoders.com" rel="nofollow noreferrer">Pycoder's Weekly</a></li> <li><a href="https://groups.google.com/forum/#!forum/comp.lang.python" rel="nofollow noreferrer">Python Google Group</a></li> </ul> <hr> <h2>Free Python programming Books</h2> <ul> <li><a href="http://en.wikibooks.org/wiki/Non-Programmer%27s_Tutorial_for_Python_2.6" rel="nofollow noreferrer">Wikibooks' Non-Programmers Tutorial for Python</a></li> <li><a href="http://docs.python.org/tutorial" rel="nofollow noreferrer">The Official Python Tutorial</a></li> <li><a href="http://www.itmaybeahack.com/homepage/books/python.html" rel="nofollow noreferrer">Building Skills in Python Version 2.6</a> (Steven F. Lott)</li> <li><a href="http://www.swaroopch.org/notes/Python" rel="nofollow noreferrer">A Byte of Python</a> (Swaroop C H.)</li> <li><a href="http://www.brpreiss.com/books/opus7/html/book.html" rel="nofollow noreferrer">Data Structures and Algorithms in Python</a> (Bruno R. Preiss)</li> <li><a href="http://www.diveintopython.net" rel="nofollow noreferrer">Dive into Python</a></li> <li><a href="http://www.diveinto.org/python3" rel="nofollow noreferrer">Dive into Python 3</a></li> <li><a href="http://www.greenteapress.com/thinkpython/thinkCSpy" rel="nofollow noreferrer">How to Think Like a Computer Scientist: Learning with Python</a> (Allen Downey, Jeff Elkner and Chris Meyers)</li> <li><a href="http://inventwithpython.com" rel="nofollow noreferrer">Invent Your Own Computer Games With Python</a> (Al Sweigart)</li> <li><a href="http://learnpythonthehardway.org" rel="nofollow noreferrer">Learn Python The Hard Way</a> (Zed A. Shaw)</li> <li><a href="http://inventwithpython.com/pygame" rel="nofollow noreferrer">Making Games with Python &amp; Pygame</a> (Albert Sweigart)</li> <li><a href="http://www.nltk.org/book" rel="nofollow noreferrer">Natural Language Processing with Python</a> (Steven Bird, Ewan Klein, and Edward Loper)</li> <li><a href="http://openbookproject.net/pybiblio" rel="nofollow noreferrer">Python Bibliotheca</a></li> <li><a href="http://openbookproject.net/py4fun" rel="nofollow noreferrer">Python for Fun</a> (Chris Meyers)</li> <li><a href="http://www.briggs.net.nz/snake-wrangling-for-kids.html" rel="nofollow noreferrer">Snake Wrangling For Kids</a> (Jason R. Briggs)</li> <li><a href="http://www.greenteapress.com/thinkpython/thinkpython.pdf" rel="nofollow noreferrer">Think Python (PDF file)</a> (Allen Downey)</li> <li><a href="http://python3porting.com" rel="nofollow noreferrer">Porting to Python 3</a> (Lennart Regebro)</li> </ul> <hr> <h2>Interactive Python learning</h2> <ul> <li><a href="http://pythonmonk.com" rel="nofollow noreferrer">Python Monk</a> - Interactive Python learning in the browser</li> <li><a href="http://www.codecademy.com/tracks/python" rel="nofollow noreferrer">Codeacademy</a> - Learn the fundamentals of Python and dynamic programming</li> <li><a href="http://www.codeskulptor.org" rel="nofollow noreferrer">CodeSkulptor</a> - Interactive online IDEfor Python programming</li> <li><a href="https://www.coursera.org/course/interactivepython" rel="nofollow noreferrer">Coursera</a> - Online course for introduction to interactive Python programming</li> <li><a href="http://www.checkio.org" rel="nofollow noreferrer">CheckiO</a> - Game world you can explore using your Python programming skills</li> <li><a href="http://www.repl.it/languages/Python" rel="nofollow noreferrer">Repl.it</a> - Online interpreter for Python that it allow saving code for later demonstration</li> </ul> <hr> <h2>Python Online Courses</h2> <ul> <li><a href="https://class.coursera.org/pythonlearn-001/auth/auth_redirector?type=login&amp;subtype=normal" rel="nofollow noreferrer">Programming for Everybody</a> - Introduction to programming using Python.</li> <li><a href="https://class.coursera.org/interactivepython-004/auth/auth_redirector?type=login&amp;subtype=normal" rel="nofollow noreferrer">An Introduction to Interactive Programming in Python</a> - The name explains itself.</li> </ul> <hr> <h2>Python for Scientists</h2> <ul> <li><a href="http://nbviewer.ipython.org/gist/rpmuller/5920182" rel="nofollow noreferrer">A Crash Course in Python for Scientists</a></li> </ul>

1994

Python is an interpreted, general-purpose high-level programming language whose design philosophy emphasizes code readability. Use the python tag for all Python related questions. If you believe your question may be even more specific, you can include a version specific tag such as python-3.x.

1995

<blockquote> <p><strong>Exercise 2.54</strong></p> <p>Two lists are said to be <code>equal?</code> if they contain equal elements arranged in the same order.</p> <p>For example,</p> <pre><code>(equal? '(this is a list) '(this is a list)) </code></pre> <p>is true, but</p> <pre><code>(equal? '(this is a list) '(this (is a) list)) </code></pre> <p>is false. To be more precise, we can define <code>equal?</code> recursively in terms of the basic <code>eq?</code> equality of symbols by saying that <code>a</code> and <code>b</code> are <code>equal?</code> if they are both symbols and the symbols are <code>eq?</code>, or if they are both lists such that <code>(car a)</code> is <code>equal?</code> to <code>(car b)</code> and <code>(cdr a)</code> is <code>equal?</code> to <code>(cdr b)</code>. Using this idea, implement <code>equal?</code> as a procedure.</p> </blockquote> <p>I wrote the following:</p> <pre><code>(define (equal? a b) (or (and (and (symbol? a) (symbol? b)) (eq? a b)) (and (null? a) (null? b)) (and (and (and (not (null? a)) (list? a)) (and (not (null? b)) (list? b))) (and (equal? (car a) (car b)) (equal? (cdr a) (cdr b)))))) </code></pre> <p>Can this be improved?</p>

1996

<blockquote> <p><strong>Exercise 2.56.</strong></p> <p>Show how to extend the basic differentiator to handle more kinds of expressions. For instance, implement the differentiation rule</p> <p>$$ \frac{d(u^n)}{dr} = nu^{n-1}(\frac{du}{dr})$$</p> <p>by adding a new clause to the deriv program and defining appropriate procedures exponentiation?, base, exponent, and make-exponentiation. (You may use the symbol ** to denote exponentiation.) Build in the rules that anything raised to the power 0 is 1 and anything raised to the power 1 is the thing itself.</p> </blockquote> <p>From the book:</p> <pre><code>(define (deriv exp var) (cond ((number? exp) 0) ((variable? exp) (if (same-variable? exp var) 1 0)) ((sum? exp) (make-sum (deriv (addend exp) var) (deriv (augend exp) var))) ((product? exp) (make-sum (make-product (multiplier exp) (deriv (multiplicand exp) var)) (make-product (deriv (multiplier exp) var) (multiplicand exp)))) </code></pre> <p>I added:</p> <pre><code> ((exponentiation? exp) (make-product (exponent exp) (make-exponentiation (base exp) (- (exponent exp) 1)))) </code></pre> <p>Book:</p> <pre><code> (else (error "unknown expression type -- DERIV" exp)))) (define (variable? x) (symbol? x)) (define (same-variable? v1 v2) (and (variable? v1) (variable? v2) (eq? v1 v2))) (define (make-sum a1 a2) (cond ((=number? a1 0) a2) ((=number? a2 0) a1) ((and (number? a1) (number? a2)) (+ a1 a2)) (else (list '+ a1 a2)))) (define (=number? exp num) (and (number? exp) (= exp num))) (define (make-product m1 m2) (cond ((or (=number? m1 0) (=number? m2 0)) 0) ((=number? m1 1) m2) ((=number? m2 1) m1) ((and (number? m1) (number? m2)) (* m1 m2)) (else (list '* m1 m2)))) (define (sum? x) (and (pair? x) (eq? (car x) '+))) (define (addend s) (cadr s)) (define (augend s) (caddr s)) (define (product? x) (and (pair? x) (eq? (car x) '*))) (define (multiplier p) (cadr p)) (define (multiplicand p) (caddr p)) </code></pre> <p>I added:</p> <pre><code>(define (exponentiation? x) (and (pair? x) (eq? (car x) '**))) (define (base s) (cadr s)) (define (exponent s) (caddr s)) (define (make-exponentiation m1 m2) (cond ((=number? m2 0) 1) ((= m2 1) m1) (else (list '** m1 m2)))) </code></pre> <p>Can this be improved?</p>

1997

<blockquote> <p>Exercise 2.57. Extend the differentiation program to handle sums and products of arbitrary numbers of (two or more) terms. Then the last example above could be expressed as</p> <p><code>(deriv '(* x y (+ x 3)) 'x)</code></p> <p>Try to do this by changing only the representation for sums and products, without changing the deriv procedure at all. For example, the addend of a sum would be the first term, and the augend would be the sum of the rest of the terms.</p> </blockquote> <p>I wrote the following solution.</p> <pre><code>(define (deriv exp var) (cond ((number? exp) 0) ((variable? exp) (if (same-variable? exp var) 1 0)) ((sum? exp) (make-sum (deriv (addend exp) var) (deriv (augend exp) var))) ((product? exp) (make-sum (make-product (multiplier exp) (deriv (multiplicand exp) var)) (make-product (deriv (multiplier exp) var) (multiplicand exp)))) ((exponentiation? exp) (make-product (exponent exp) (make-exponentiation (base exp) (- (exponent exp) 1)))) (else (error "unknown expression type -- DERIV" exp)))) (define (variable? x) (symbol? x)) (define (same-variable? v1 v2) (and (variable? v1) (variable? v2) (eq? v1 v2))) (define (make-sum . a) (define (iter sum rest) (cond ((null? rest) (if (zero? sum) '() (list sum))) ((=number? (car rest) 0) (iter sum (cdr rest))) ((number? (car rest)) (iter (+ sum (car rest)) (cdr rest))) (else (cons (car rest) (iter sum (cdr rest)))))) (let ((result (iter 0 a))) (if (= (length result) 1) (car result) (cons '+ result)))) (define (=number? exp num) (and (number? exp) (= exp num))) (define (make-product . a) (define (iter product rest) (cond ((null? rest) (if (= 1 product) '() (list product))) ((=number? (car rest) 1) (iter product (cdr rest))) ((number? (car rest)) (iter (* product (car rest)) (cdr rest))) (else (let ((result (iter product (cdr rest)))) (if (and (pair? result) (eq? (car result) 0)) (list 0) (cons (car rest) result)))))) (let ((result (iter 1 a))) (if (= (length result) 1) (car result) (cons '* result)))) (define (sum? x) (and (pair? x) (eq? (car x) '+))) (define (addend s) (cadr s)) (define (augend s) (if (&gt; (length s) 3) (cons '+ (cddr s)) (caddr s))) (define (product? x) (and (pair? x) (eq? (car x) '*))) (define (multiplier p) (cadr p)) (define (multiplicand p) (if (&gt; (length p) 3) (cons '* (cddr p)) (caddr p))) (define (exponentiation? x) (and (pair? x) (eq? (car x) '**))) (define (base s) (cadr s)) (define (exponent s) (caddr s)) (define (make-exponentiation m1 m2) (cond ((=number? m2 0) 1) ((= m2 1) m1) (else (list '** m1 m2)))) </code></pre> <p>Can it be improved? In particular, look closely at make-product and make-sum.</p>

1998

<p>I am making a website using the MVP pattern. It is a simple website, so for the repository I use Linq2SQL. My architecture is basically:</p> <p>(View - Presenter) - Service Layer - Domain Models.</p> <p>The View consists of 10 dropdownlists, and a submit button.</p> <p>Between the (View - Presenter) and the Service Layer I use DTO's to exchange information. But here is as well where my problem lies; the Service Layer gets the data from the DataContext. This data is in all sorts of types, ints, strings, etc. My View mostly needs everything in strings. Now I need to fill a DTO to send to the Presenter. The question is if I should already format everything so that it can be consumed by the presenter/view, or should the Presenter do this? For now, I have the Presenter do it, but I find the code a bit ghastly. Please review my code (p.s I am aware I should use DI - it will be applied ;-)):</p> <pre><code>using Business; using System.Collections.Generic; using Service; using DTOs; using System.Text; namespace Web { public class PredictionDetailsPresenter { private readonly IDriverService driverService; private readonly IPredictionDetailsView predictionDetailsView; private readonly IPredictionService predictionService; #region constructors public PredictionDetailsPresenter(IPredictionDetailsView predictionDetailsView) : this(predictionDetailsView, new DriverService(), new PredictionService()) { } public PredictionDetailsPresenter(IPredictionDetailsView predictionDetailsView, IDriverService driverService, IPredictionService predictionService) { this.predictionDetailsView = predictionDetailsView; this.driverService = driverService; this.predictionService = predictionService; } #endregion #region public methods public void Initialize() { predictionDetailsView.SetFirstListItemOfPositionDropDownLists(" ---Select Driver--- "); foreach (Driver driver in driverService.GetAllDrivers()) { predictionDetailsView.AddDriver(driver.Name, driver.Id.ToString()); } PredictionServiceInitializeResponse response = predictionService.Initialize("Belgian Grand Prix"); predictionDetailsView.RaceId = response.RaceId.ToString(); predictionDetailsView.DateAndTimeOfRace = response.DateAndTimeOfRace.ToString(); predictionDetailsView.RaceTitle = response.RaceTitle; predictionDetailsView.SelectedDriverIdDriverPolePosition = (response.SelectedDrivers[(int)DriverPositions.PolePosition]).ToString(); predictionDetailsView.SelectedDriverIdDriver2ndPosition = (response.SelectedDrivers[(int)DriverPositions.SecondPosition]).ToString(); predictionDetailsView.SelectedDriverIdDriver3rdPosition = (response.SelectedDrivers[(int)DriverPositions.ThirdPosition]).ToString(); predictionDetailsView.SelectedDriverIdDriver4thPosition = (response.SelectedDrivers[(int)DriverPositions.FourthPosition]).ToString(); predictionDetailsView.SelectedDriverIdDriver5thPosition = (response.SelectedDrivers[(int)DriverPositions.FifthPosition]).ToString(); predictionDetailsView.SelectedDriverIdDriver6thPosition = (response.SelectedDrivers[(int)DriverPositions.SixthPosition]).ToString(); predictionDetailsView.SelectedDriverIdDriver7thPosition = (response.SelectedDrivers[(int)DriverPositions.SeventhPosition]).ToString(); predictionDetailsView.SelectedDriverIdDriver8thPosition = (response.SelectedDrivers[(int)DriverPositions.EightPosition]).ToString(); predictionDetailsView.SelectedDriverIdDriver9thPosition = (response.SelectedDrivers[(int)DriverPositions.NinthPosition]).ToString(); predictionDetailsView.SelectedDriverIdDriver10thPosition = (response.SelectedDrivers[(int)DriverPositions.TenthPosition]).ToString(); } public void ProcessPrediction() { PredictionServiceInsertRequest predictionServiceInsertRequest = new PredictionServiceInsertRequest(); predictionServiceInsertRequest.SelectedDrivers.Add(DriverPositions.PolePosition.ToString(), new Driver { Id = int.Parse(predictionDetailsView.SelectedDriverIdDriverPolePosition), Name = predictionDetailsView.SelectedNameDriverPolePosition }); predictionServiceInsertRequest.SelectedDrivers.Add(DriverPositions.SecondPosition.ToString(), new Driver { Id = int.Parse(predictionDetailsView.SelectedDriverIdDriver2ndPosition), Name = predictionDetailsView.SelectedNameDriver2ndPosition }); predictionServiceInsertRequest.SelectedDrivers.Add(DriverPositions.ThirdPosition.ToString(), new Driver { Id = int.Parse(predictionDetailsView.SelectedDriverIdDriver3rdPosition), Name = predictionDetailsView.SelectedNameDriver3rdPosition }); predictionServiceInsertRequest.SelectedDrivers.Add(DriverPositions.FourthPosition.ToString(), new Driver { Id = int.Parse(predictionDetailsView.SelectedDriverIdDriver4thPosition), Name = predictionDetailsView.SelectedNameDriver4thPosition }); predictionServiceInsertRequest.SelectedDrivers.Add(DriverPositions.FifthPosition.ToString(), new Driver { Id = int.Parse(predictionDetailsView.SelectedDriverIdDriver5thPosition), Name = predictionDetailsView.SelectedNameDriver5thPosition }); predictionServiceInsertRequest.SelectedDrivers.Add(DriverPositions.SixthPosition.ToString(), new Driver { Id = int.Parse(predictionDetailsView.SelectedDriverIdDriver6thPosition), Name = predictionDetailsView.SelectedNameDriver6thPosition }); predictionServiceInsertRequest.SelectedDrivers.Add(DriverPositions.SeventhPosition.ToString(), new Driver { Id = int.Parse(predictionDetailsView.SelectedDriverIdDriver7thPosition), Name = predictionDetailsView.SelectedNameDriver7thPosition }); predictionServiceInsertRequest.SelectedDrivers.Add(DriverPositions.EightPosition.ToString(), new Driver { Id = int.Parse(predictionDetailsView.SelectedDriverIdDriver8thPosition), Name = predictionDetailsView.SelectedNameDriver8thPosition }); predictionServiceInsertRequest.SelectedDrivers.Add(DriverPositions.NinthPosition.ToString(), new Driver { Id = int.Parse(predictionDetailsView.SelectedDriverIdDriver9thPosition), Name = predictionDetailsView.SelectedNameDriver9thPosition }); predictionServiceInsertRequest.SelectedDrivers.Add(DriverPositions.TenthPosition.ToString(), new Driver { Id = int.Parse(predictionDetailsView.SelectedDriverIdDriver10thPosition), Name = predictionDetailsView.SelectedNameDriver10thPosition }); predictionServiceInsertRequest.RaceId = predictionDetailsView.RaceId; PredictionServiceInsertResponse response = predictionService.Insert(predictionServiceInsertRequest); if (response.Success) { predictionDetailsView.Message = "Your prediction has been inserted succesfully"; } else { StringBuilder sb = new StringBuilder(); foreach (var error in response.Errors) { sb.AppendFormat("{0}&lt;br /&gt;", error); } predictionDetailsView.Message = sb.ToString(); } } #endregion } public enum DriverPositions { PolePosition = 1, SecondPosition = 2, ThirdPosition = 3, FourthPosition = 4, FifthPosition = 5, SixthPosition = 6, SeventhPosition = 7, EightPosition = 8, NinthPosition = 9, TenthPosition = 10 } } </code></pre>

2002

<p><strong>Background</strong>:<br> This began with <a href="http://jcoglan.com/">James Colgan</a>'s <a href="https://github.com/jcoglan/lisp-dojo">Lisp-Dojo</a> for Ruby. My implementation can be found <a href="https://github.com/antarestrader/lisp-dojo">here</a>. I then moved on to <a href="http://en.wikibooks.org/wiki/Write_Yourself_a_Scheme_in_48_Hours">Write yourself a scheme in 48 hours</a>. This question has to do with one of the implementation decisions.</p> <p><strong>Code</strong>:</p> <p>My implementation of <code>eval</code> </p> <pre><code>--# The eval function takes a scope and paresed Lisp value and --# returns the resulting Lisp Value. --# String, Number and Bool return themselves. --# An Atom trys to find its self in the scope and retrun that value --# A List is evaluated using the normal Lisp rules. eval :: LispScope-&gt; LispVal -&gt; IOThrowsError LispVal eval s val@(String _) = return val eval s (Atom val) = do (liftIO $ getValue s val) &gt;&gt;= maybe (throwError $ "Value not in scope: " ++ val) (return) eval s val@(Number _) = return val eval s val@(Bool _) = return val eval scope (List (fn:lvs)) = do fun &lt;- eval scope fn case fun of Syntax f _-&gt; f scope lvs Function f _-&gt; evalMap scope lvs &gt;&gt;= f val -&gt; throwError $ (show val) ++ " is not a function" eval scope (List []) = return $ List [] eval _ badForm = throwError $ "Unrecognized form: " ++ show badForm </code></pre> <p>Note two things: 1) I do not refer to any special forms, 2) the use of Syntax for hygenic forms.</p> <p>This is a piece of code from <a href="http://en.wikibooks.org/wiki/Write_Yourself_a_Scheme_in_48_Hours">Write yourself a scheme in 48 hours</a>:</p> <pre><code>--# evaluate the "if" form eval (List [Atom "if", pred, conseq, alt]) = do result &lt;- eval pred case result of Bool False -&gt; eval alt otherwise -&gt; eval conseq </code></pre> <p>Note that in the tutorial the form is written directly into the eval function. This pattern is followed for other syntaxes like <code>define</code> and <code>lambda</code>.</p> <p><strong>Question</strong>: When I implemented my version I followed what I thought was a wise choice demonstrated in <a href="https://github.com/jcoglan/lisp-dojo/tree/jcoglan">James Colgan's solution</a> to the lisp-dojo to keep eval as simple as possible and instead to push the syntax implementations into the root scope. eg:</p> <pre><code>ifSyntax :: LispScope -&gt; [LispVal] -&gt; IOThrowsError LispVal ifSyntax s [pred, consequent, alternate] = do pred' &lt;- eval s pred case pred' of Bool False -&gt; eval s alternate otherwise -&gt; eval s consequent ifSyntax _ _ = throwError "if: Bad Syntax" ifVal = (Syntax ifSyntax $ Left "syntax (if)") --# this is then added to the initial scope </code></pre> <p><strong>I would like to know why one choice might be better then the other, and what is typical in real-world implementations.</strong></p> <p><strong>Reference</strong>:</p> <p>My definition of the <code>LispVal</code> data type:</p> <pre><code>type LispScope = Scope LispVal data Lambda = Lambda {params :: [String], body :: [LispVal]} data LispVal = Atom String | List [LispVal] | Number Integer | Real Double | String String | Function ([LispVal] -&gt; IOThrowsError LispVal) (Either String Lambda) | Syntax (LispScope -&gt; [LispVal] -&gt; IOThrowsError LispVal) (Either String Lambda) | Bool Bool | Port Handle </code></pre>

2003

<p>I just started learning how to code PHP as well as HTML and as a challenge for myself I put together a questionnaire with what I have learnt so far which isn't as much as I would like to know e.g. sessions, databases, etc. Anyhoo, I would like to get the review of peers and would appreciate any constructive suggestions, ideas, etc. Here it does... <pre><code>//Initialize page $startpage = isset($_POST['page']) ? $_POST['page'] : 1; $endpage = 11; //Initialize score $score = isset($_POST['score']) ? $_POST['score'] : 0; if(isset($_POST['submit'])) { $questions = array('question1' =&gt; 'superglobal', 'question2' =&gt; 'formsubmission', 'question3' =&gt; 'declare', 'question4' =&gt; 'symbol', 'question5' =&gt; 'statement', 'question6' =&gt; 'division', 'question7' =&gt; 'codeans', 'question8' =&gt; 'email', 'question9' =&gt; 'super', 'question10' =&gt; 'switch'); foreach($questions as $questionkey =&gt; $questionvalue) { $questionpost = isset($_POST[$questionvalue]) ? $_POST[$questionvalue] : ''; if($questionkey == 'question'.$startpage &amp;&amp; empty($questionpost)) { $errormsg = 'Please select an answer for '. $questionkey; echo $errormsg . '&lt;br /&gt;'; } } //Answers $answers = array('question1' =&gt; 'if', 'question2' =&gt; 'post', 'question3' =&gt; '$a', 'question4' =&gt; ';', 'question5' =&gt; '3', 'question6' =&gt; '%', 'question7' =&gt; 'infinite', 'question8' =&gt; 'mail', 'question9' =&gt; array('get', 'post', 'request'), 'question10' =&gt; array('break')); //Loop through post array foreach($questions as $questionkey =&gt; $questionvalue) { // echo $postkey. '=' .$postvalue; if(!empty($_POST[$questionvalue]) &amp;&amp; $questionkey == 'question'.$startpage) { //Loop through answers foreach($answers as $key =&gt; $value) { if(is_array($value)) { foreach($value as $arraykey =&gt; $arrayvalue) { if($questionkey == $key &amp;&amp; $_POST[$questionvalue][$arraykey] == $arrayvalue) { // echo $key. '=' .$arrayvalue; echo 'Your answer for '. $questionkey .' was correct'; $startpage = $startpage + 1; $score = $score + 1; break; } else if($questionkey == $key &amp;&amp; $_POST[$questionvalue][$arraykey] != $arrayvalue) { echo 'Your answer for '. $questionkey .' was incorrect'; echo $_POST[$questionvalue][$arraykey]; break; } } } else { if($questionkey == $key &amp;&amp; $_POST[$questionvalue] == $value) { // echo $key. '=' .$value. '&lt;br /&gt;'; echo 'Your answer for '. $questionkey .' was correct'; $startpage = $startpage + 1; $score = $score + 1; // echo $questionkey; // echo $key; break; } else if($questionkey == $key &amp;&amp; $_POST[$questionvalue] != $value) { echo 'Your answer for '. $questionkey .' is incorrect'; // echo $questionvalue; // echo $questionkey; // echo $key; break; } } } } } //Debug // print_r($_POST); } ?&gt; &lt;!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"&gt; &lt;html&gt; &lt;head&gt; &lt;title&gt;Questionnaire&lt;/title&gt; &lt;/head&gt; &lt;body&gt; &lt;h1&gt;Questionnaire&lt;/h1&gt; &lt;p&gt;This is a sample questionnaire that you can take and evaluate your results. Below are some tips&lt;/p&gt; &lt;ol&gt; &lt;li&gt;This questionnaire has total of 10 questions&lt;/li&gt; &lt;li&gt;Each question is worth 1 point totalling 10 points&lt;/li&gt; &lt;li&gt;There are 8 multiple choice and 2 multi-select questions&lt;/li&gt; &lt;li&gt;At the end of the questionnaire, you'll be presented with your score&lt;/li&gt; &lt;/ol&gt; &lt;form name="questionnaire" method="post" action="questionnaire.php"&gt; &lt;?php echo '&lt;input type="hidden" name="page" value="'. $startpage. '"&gt;'; echo '&lt;input type="hidden" name="score" value="' . $score .'"&gt;'; switch($startpage) { case(1): echo '&lt;div&gt; Question 1. Which one of these is a super global? &lt;br /&gt; &lt;input type="radio" name="superglobal" value="if"&gt;if &lt;input type="radio" name="superglobal" value="and"&gt;and &lt;input type="radio" name="superglobal" value="get"&gt;GET &lt;input type="radio" name="superglobal" value="array"&gt;array &lt;/div&gt;'; break; case(2): echo '&lt;div&gt; Question 2. Which one of these hides the values when submitting a form? &lt;br /&gt; &lt;input type="radio" name="formsubmission" value="get"&gt;GET &lt;input type="radio" name="formsubmission" value="send"&gt;SEND &lt;input type="radio" name="formsubmission" value="parcel"&gt;PARCEL &lt;input type="radio" name="formsubmission" value="post"&gt;POST &lt;/div&gt;'; break; case(3): echo '&lt;div&gt; Question 3. Select which one these is the correct way of declaring a variable? &lt;br /&gt; &lt;input type="radio" name="declare" value="a"&gt;a &lt;input type="radio" name="declare" value="$a"&gt;$a &lt;input type="radio" name="declare" value="%a"&gt;%a &lt;input type="radio" name="declare" value="%a"&gt;%a &lt;/div&gt;'; break; case(4): echo '&lt;div&gt; Question 4. Which symbol would you have at the end of a statemement &lt;br /&gt; &lt;input type="radio" name="symbol" value=";"&gt;; &lt;input type="radio" name="symbol" value="#"&gt;# &lt;input type="radio" name="symbol" value="*"&gt;* &lt;input type="radio" name="symbol" value="/"&gt;/ &lt;/div&gt;'; break; case(5): echo '&lt;div&gt; Question 5. Select which one of these statements is true? &lt;br /&gt; &lt;input type="radio" name="statement" value="2"&gt;a++ equals to 2 if a is 1 &lt;input type="radio" name="statement" value="3"&gt;++a is equals to 3 if a is 2 &lt;input type="radio" name="statement" value="divide"&gt;\ is the symbol for divisions &lt;input type="radio" name="statement" value="zero"&gt;0 is the value that represents true &lt;/div&gt;'; break; case(6): echo '&lt;div&gt; Question 6. Which symbol gives the remainder in a division? &lt;br /&gt; &lt;input type="radio" name="division" value=")"&gt;) &lt;input type="radio" name="division" value="}"&gt;} &lt;input type="radio" name="division" value="%"&gt;% &lt;input type="radio" name="division" value=";")&gt;; &lt;/div&gt;'; break; case(7): echo '&lt;div&gt; Question 7. What will the code below return &lt;br /&gt; &lt;pre&gt; $a=1 while($a &lt; 10) { echo $a; } &lt;/pre&gt; &lt;input type="radio" name="codeans" value="one"&gt;1 &lt;input type="radio" name="codeans" value="zero"&gt;0 &lt;input type="radio" name="codeans" value="infinite"&gt;infinite loop &lt;input type="radio" name="codeans" value="3"&gt;3 &lt;/div&gt;'; break; case(8): echo '&lt;div&gt; Question 8. What function can you use to send an email &lt;br /&gt; &lt;input type="radio" name="email" value="mail"&gt;mail &lt;input type="radio" name="email" value="email"&gt;email &lt;input type="radio" name="email" value="mailto"&gt;mailto &lt;input type="radio" name="email" value="send"&gt;send &lt;/div&gt;'; break; case(9): echo '&lt;div&gt; Question 9. Which of the following are super-globals?&lt;br /&gt; &lt;input type="checkbox" name="super[]" value="get"&gt;GET &lt;input type="checkbox" name="super[]" value="post"&gt;POST &lt;input type="checkbox" name="super[]" value="request"&gt;REQUEST &lt;input type="checkbox" name="super[]" value="process"&gt;PROCESS &lt;/div&gt;'; break; case(10): echo '&lt;div&gt; Question 10. Which of the following are true to exit a switch statement? &lt;br /&gt; &lt;input type="checkbox" name="switch[]" value="exit"&gt;exit &lt;input type="checkbox" name="switch[]" value="die"&gt;die &lt;input type="checkbox" name="switch[]" value="drop"&gt;drop &lt;input type="checkbox" name="switch[]" value="break"&gt;break &lt;/div&gt;'; break; case(11): echo 'Congratulations, you have completed the test and you scored.'. $score; break; } ?&gt; &lt;?php if($startpage &lt; $endpage) { echo '&lt;div&gt;&lt;input type="submit" name="submit" value="submit"&gt;&lt;/div&gt;'; } ?&gt; &lt;/form&gt; &lt;/body&gt; &lt;/html&gt; </code></pre>

2004

<p>How can I make this sort faster and better?</p> <pre><code>function OrderBy(a,b) { if (a &lt; b) return -1; if (a &gt; b) return 1; return 0; } SortBy = function($th) { var $tbody = $th.closest('tbody'); var $table = $tbody.parent(); $tbody.detach(); $('#Processing').show('fast',function () { var column = $th.index(); var rows = $tbody.find('tr').get(); rows.sort(function(rowA,rowB) { var keyA = $(rowA).children('td').eq(column).text(); var keyB = $(rowB).children('td').eq(column).text(); return OrderBy(keyA,keyB); }); $.each(rows, function(index,row) { $tbody.append(row); }); $table.append($tbody); }); }; </code></pre>

2006

<pre><code>if params[:package] city_ids = [] city = params[:package].delete 'city' city_ids &lt;&lt; city if city.to_i &gt; 0 cities = params[:package].delete 'cities' city_ids += cities if cities.class == Array &amp;&amp; cities.length &gt; 0 params[:package][:cities] = city_ids.map{ |c| City.get(c) }.compact end </code></pre>

2007

<p>I had some difficulty with this problem, so I'm sure there is a better way. Here is the question from <a href="http://mitpress.mit.edu/sicp/full-text/book/book-Z-H-16.html" rel="nofollow">SICP</a>:</p> <blockquote> <p><strong>Exercise 2.58</strong></p> <p>Suppose we want to modify the differentiation program so that it works with ordinary mathematical notation, in which + and * are infix rather than prefix operators. Since the differentiation program is defined in terms of abstract data, we can modify it to work with different representations of expressions solely by changing the predicates, selectors, and constructors that define the representation of the algebraic expressions on which the differentiator is to operate.</p> <p><strong>a.</strong> Show how to do this in order to differentiate algebraic expressions presented in infix form, such as</p> <pre><code>(x + (3 * (x + (y + 2)))) </code></pre> <p>To simplify the task, assume that + and * always take two arguments and that expressions are fully parenthesized.</p> <p><strong>b.</strong> The problem becomes substantially harder if we allow standard algebraic notation, such as</p> <pre><code>(x + 3 * (x + y + 2)) </code></pre> <p>which drops unnecessary parentheses and assumes that multiplication is done before addition. Can you design appropriate predicates, selectors, and constructors for this notation such that our derivative program still works?</p> </blockquote> <p>I wrote the following solution to part b (some parts came from the text):</p> <pre><code>(define (deriv exp var) (cond ((number? exp) 0) ((variable? exp) (if (same-variable? exp var) 1 0)) ((sum? exp) (make-sum (deriv (addend exp) var) (deriv (augend exp) var))) ((product? exp) (make-sum (make-product (multiplier exp) (deriv (multiplicand exp) var)) (make-product (deriv (multiplier exp) var) (multiplicand exp)))) (else (error "unknown expression type -- DERIV" exp)))) (define (variable? x) (symbol? x)) (define (same-variable? v1 v2) (and (variable? v1) (variable? v2) (eq? v1 v2))) (define (join op seq) (foldr (lambda (a b) (cons a (if (null? b) b (cons op b)))) null seq)) (define (make-sum . a) (define (iter sum rest) (cond ((null? rest) (if (zero? sum) '() (list sum))) ((=number? (car rest) 0) (iter sum (cdr rest))) ((number? (car rest)) (iter (+ sum (car rest)) (cdr rest))) (else (cons (car rest) (iter sum (cdr rest)))))) (let ((result (iter 0 a))) (cond ((null? result) 0) ((= (length result) 1) (car result)) (else (join '+ result))))) (define (=number? exp num) (and (number? exp) (= exp num))) (define (make-product . a) (define (iter product rest) (cond ((null? rest) (if (= 1 product) '() (list product))) ((=number? (car rest) 1) (iter product (cdr rest))) ((number? (car rest)) (iter (* product (car rest)) (cdr rest))) (else (let ((result (iter product (cdr rest)))) (if (and (pair? result) (eq? (car result) 0)) (list 0) (cons (car rest) result)))))) (let ((result (iter 1 a))) (cond ((null? result) 1) ((eq? (length result) 1) (car result)) (else (join '* result))))) (define (sum? x) (and (pair? x) (or (member '+ x) (and (eq? 1 (length x)) (pair? (car x)) (pair? (member '+ (car x))))))) (define (items-before op seq) (if (eq? (cadr seq) op) (list (car seq)) (cons (car seq) (items-before op (cdr seq))))) (define (items-after op seq) (if (eq? (car seq) op) (cdr seq) (items-after op (cdr seq)))) (define (addend s) (if (and (eq? (length s) 1) (pair? (car s))) (addend (car s)) (let ((result (items-before '+ s))) (if (eq? 1 (length result)) (car result) result)))) (define (augend s) (if (and (eq? (length s) 1) (pair? (car s))) (augend (car s)) (let ((result (items-after '+ s))) (if (eq? 1 (length result)) (car result) result)))) (define (product? x) (define (no-plus-just-times seq) (not (member '+ seq)) (pair? (member '* seq))) (and (pair? x) (or (and (no-plus-just-times x)) (and (eq? (length x) 1) (pair? (car x)) (no-plus-just-times (car x)))))) (define (multiplier p) (if (and (eq? (length p) 1) (pair? (car p))) (multiplier (car p)) (car p))) (define (multiplicand p) (if (eq? (length p) 1) (if (pair? (car p)) (multiplicand (car p)) (car p)) (caddr p))) </code></pre> <p>How can this be improved?</p>

2009

<p>For web-uploading of Cyrillic-named images, I've written the script below:</p> <pre><code>#!/usr/bin/python # coding=utf-8 import os import argparse import shutil class Error: pass class FolderError(Error): pass def copytranstree (src, dst): names = os.listdir( src ) try: os.makedirs( dst ) except WindowsError: pass errors = [] for name in names: srcname = os.path.join( src, name ) dstname = os.path.join( dst, ''.join([translit.get(x, x) for x in name.decode( input_parametres.encoding ).lower()]).encode( input_parametres.encoding ) ) try: if os.path.isdir( srcname ): copytranstree( srcname, dstname ) else: shutil.copy2( srcname, dstname ) except (IOError, os.error), why: errors.append( ( srcname, dstname, str( why ) )) except Error, err: errors.extend( err.args[0] ) try: shutil.copystat( src, dst ) except WindowsError: pass except OSError, why: errors.extend( (src, dst, str(why) ) ) if errors: raise Error( errors ) parser = argparse.ArgumentParser(description='Copy directory tree with transliterated pathnames') parser.add_argument('-e','--encoding', help='File system encoding', default='utf-8') parser.add_argument('-s','--src', help='Source folder name', default='./' ) parser.add_argument('-d','--dst', help='Destination folder name', default='./') input_parametres = parser.parse_args() translit = dict(zip(u"абвгдеёзийклмнопрстуфхьъ", "abvgdeeziyklmnoprstufh'~")) translit.update({u'ц': 'tz', u'ч': 'ch', u'ш': 'sh', u'ы': 'yi', u'э': 'ye', u'ю': 'ju', u'я': 'ja', u' ': '_'}) src = os.path.abspath( input_parametres.src ) dst = os.path.abspath( input_parametres.dst ) if not os.path.exists( dst ): dstname = ''.join([translit.get(x, x) for x in dst.decode( input_parametres.encoding ).lower()]).encode( input_parametres.encoding ).lower() os.makedirs( dstname ) dst = os.path.abspath( dstname ) if not os.path.exists( src ) or os.path.isfile( dst ): raise FolderError() copytranstree( src, dst ) </code></pre> <p>The script transliterates and copies a tree of files from a source folder to destination, considering encoding passed to the script (UTF for Ubuntu, CP121 for Windows).</p> <p>Any ideas for common improvement of structure for Linux OS?</p>

2011

<p>From <a href="http://mitpress.mit.edu/sicp/full-text/book/book-Z-H-16.html" rel="nofollow">SICP</a>:</p> <blockquote> <p>Exercise 2.60. We specified that a set would be represented as a list with no duplicates. Now suppose we allow duplicates. For instance, the set {1,2,3} could be represented as the list (2 3 2 1 3 2 2). Design procedures element-of-set?, adjoin-set, union-set, and intersection-set that operate on this representation. How does the efficiency of each compare with the corresponding procedure for the non-duplicate representation? Are there applications for which you would use this representation in preference to the non-duplicate one?</p> </blockquote> <p>I wrote the following solution (some parts came from the book):</p> <pre><code>(define (element-of-set? x set) (cond ((null? set) false) ((equal? x (car set)) true) (else (element-of-set? x (cdr set))))) (define adjoin-set cons) (define (intersection-set set1 set2) (cond ((or (null? set1) (null? set2)) '()) ((element-of-set? (car set1) set2) (cons (car set1) (intersection-set (cdr set1) set2))) (else (intersection-set (cdr set1) set2)))) (define (union-set set1 set2) (cond ((null? set1) set2) ((null? set2) set1) (else (cons (car set1) (union-set (cdr set1) set2)))))1) </code></pre>

2012

<p>From <a href="http://mitpress.mit.edu/sicp/full-text/book/book-Z-H-16.html" rel="nofollow">SICP</a>:</p> <blockquote> <p><strong>Exercise 2.61</strong></p> <p>Give an implementation of adjoin-set using the ordered representation. By analogy with element-of-set? show how to take advantage of the ordering to produce a procedure that requires on the average about half as many steps as with the unordered representation.</p> </blockquote> <pre><code>(define (adjoin-set x set) (define (rec subset) (cond ((null? subset) (list x)) ((&gt; x (car subset)) (cons (car subset) (rec (cdr subset)))) (else (cons x subset)))) (if (element-of-set? x set) set (rec set))) </code></pre> <p>Can this be improved?</p>

2013

<p>I've just finished the Ruby Koans and one of the last projects was creating a Proxy class that sends methods to another class. I was wondering whether you would change anything about my solution (if there's something wrong or a better way to do it). I'm still a beginner and I want to get better.</p> <pre><code>require File.expand_path(File.dirname(__FILE__) + '/edgecase') # Project: Create a Proxy Class # # In this assignment, create a proxy class (one is started for you # below). You should be able to initialize the proxy object with any # object. Any messages sent to the proxy object should be forwarded # to the target object. As each message is sent, the proxy should # record the name of the method send. # # The proxy class is started for you. You will need to add a method # missing handler and any other supporting methods. The specification # of the Proxy class is given in the AboutProxyObjectProject koan. class Proxy attr_reader(:messages) def method_missing(method_name, *args, &amp;block) if @methods_to_pass.include?(method_name.to_s) @messages &lt;&lt; method_name @object.__send__(method_name, *args, &amp;block) else super(method_name, *args, &amp;block) end end def called?(method_name) @messages.include?(method_name) end def number_of_times_called(method_name) @messages.count(method_name) end def initialize(target_object) @methods_to_pass, @messages = [], [] @object = target_object @object.class.instance_methods(true).each { |method_name| @methods_to_pass &lt;&lt; method_name; method_name } end end # The proxy object should pass the following Koan: # class AboutProxyObjectProject &lt; EdgeCase::Koan def test_proxy_method_returns_wrapped_object # NOTE: The Television class is defined below tv = Proxy.new(Television.new) assert tv.instance_of?(Proxy) end def test_tv_methods_still_perform_their_function tv = Proxy.new(Television.new) tv.channel = 10 tv.power assert_equal 10, tv.channel assert tv.on? end def test_proxy_records_messages_sent_to_tv tv = Proxy.new(Television.new) tv.power tv.channel = 10 assert_equal [:power, :channel=], tv.messages end def test_proxy_handles_invalid_messages tv = Proxy.new(Television.new) assert_raise(NoMethodError) do tv.no_such_method end end def test_proxy_reports_methods_have_been_called tv = Proxy.new(Television.new) tv.power tv.power assert tv.called?(:power) assert ! tv.called?(:channel) end def test_proxy_counts_method_calls tv = Proxy.new(Television.new) tv.power tv.channel = 48 tv.power assert_equal 2, tv.number_of_times_called(:power) assert_equal 1, tv.number_of_times_called(:channel=) assert_equal 0, tv.number_of_times_called(:on?) end def test_proxy_can_record_more_than_just_tv_objects proxy = Proxy.new("Code Mash 2009") proxy.upcase! result = proxy.split assert_equal ["CODE", "MASH", "2009"], result assert_equal [:upcase!, :split], proxy.messages end end # ==================================================================== # The following code is to support the testing of the Proxy class. No # changes should be necessary to anything below this comment. # Example class using in the proxy testing above. class Television attr_accessor :channel def power if @power == :on @power = :off else @power = :on end end def on? @power == :on end end # Tests for the Television class. All of theses tests should pass. class TelevisionTest &lt; EdgeCase::Koan def test_it_turns_on tv = Television.new tv.power assert tv.on? end def test_it_also_turns_off tv = Television.new tv.power tv.power assert ! tv.on? end def test_edge_case_on_off tv = Television.new tv.power tv.power tv.power assert tv.on? tv.power assert ! tv.on? end def test_can_set_the_channel tv = Television.new tv.channel = 11 assert_equal 11, tv.channel end end </code></pre>

2015

<p>From <a href="http://mitpress.mit.edu/sicp/full-text/book/book-Z-H-16.html" rel="nofollow">SICP</a>:</p> <blockquote> <p><strong>Exercise 2.65</strong></p> <p>Use the results of exercises 2.63 and 2.64 to give (n) implementations of union-set and intersection-set for sets implemented as (balanced) binary trees.41</p> </blockquote> <p>I wrote the following answer:</p> <pre><code>(define (union-set a b) (define (rec set1 set2) (cond ((null? set1) set2) ((null? set2) set1) ((= (car set1) (car set2)) (cons (car set1) (union-set (cdr set1) (cdr set2)))) ((&gt; (car set1) (car set2)) (cons (car set1) (union-set (cdr set1) set2))) (else (cons (car set2) (rec set1 (cdr set2)))))) (let ((ls-result (rec (tree-&gt;list a) (tree-&gt;list b)))) (partial-tree ls-result (length ls-result)))) (define (intersection-set a b) (define (rec set1 set2) (cond ((or (null? set1) (null? set2)) '()) ((= (car set1) (car set2)) (cons (car set1) (rec (cdr set1) (cdr set2)))) ((&gt; (car set1) (car set2)) (rec set1 (cdr set2))) ((&gt; (car set2) (car set1)) (rec (cdr set1) set2)))) (let ((ls-result (rec (tree-&gt;list a) (tree-&gt;list b)))) (partial-tree ls-result (length ls-result)))) </code></pre> <p>Is this answer ok? Could it be better?</p>

2018

<p>I'm writing a function with the following signature:</p> <pre><code>(Ord a) =&gt; [a] -&gt; [Int] </code></pre> <p>It's semantics is to find an order-preserving mapping from list of objects to list of <code>Int</code>s.</p> <p>The version of mine:</p> <pre><code>import Data.List import Data.Map (Map, (!)) import qualified Data.Map as Map renumber :: (Ord a) =&gt; [a] -&gt; [Int] renumber list = let mapping = buildmapping list Map.empty in map (mapping!) list where -- buildmapping :: (Ord a) =&gt; [a] -&gt; Map a Int -&gt; Map a Int buildmapping list mapping = let mapped = Map.keys mapping (rest, nextindex) = if (null mapped) then (list, 1) else (filter (&gt; maximum mapped) list, (1+) $ maximum $ Map.elems mapping) in case rest of [] -&gt; mapping -- nothing left, return _ -&gt; buildmapping rest $ Map.insert (minimum rest) nextindex mapping </code></pre>

2019

<p>I have ext_scaffold (<code>question.js</code>). When I row click I get answers on this question, so</p> <pre><code>'rowselect': function(sm, row, rec) { store = new Ext.data.Store({ proxy: new Ext.data.HttpProxy({ url: '/answers/index_all_for_question_id/' + rec.data.id + '?format=ext_json', method: 'GET'}), reader: new Ext.data.JsonReader({ root: 'answers', id: 'id', totalProperty: 'results' }, [ {name: 'text', mapping: 'answer.text'}, {name: 'email', mapping: 'answer.respondent.email'} ]) }); grid = Ext.getCmp('answers_grid'); grid.reconfigure(store, new Ext.grid.ColumnModel([ {id: 'text', header: "Answer &amp;darr;", width: 500, sortable: true, dataIndex: 'text'}, {id: 'email', header: "Email", width: 300, sortable: true, dataIndex: 'email'} ])); grid.store.load(); scaffoldPanel.selectedRecordId = rec.data.id; scaffoldPanel.getFormPanel().getForm().loadRecord(rec); } </code></pre> <p>and I have another admin file where grids (answer):</p> <pre><code> var answers_datastore = new Ext.data.Store({ autoLoad: true, proxy: new Ext.data.HttpProxy({ url: '/answers/index_all_for_question_id/&lt;%= @questions.first.id %&gt;?format=ext_json', method: 'GET'}), reader: new Ext.data.JsonReader({ root: 'answers', id: 'id', totalProperty: 'results' },[ {name: 'text', mapping: 'answer.text'}, {name: 'email', mapping: 'answer.respondent.email'} ]) }); var answersGrid = new Ext.grid.GridPanel({ id: 'answers_grid', store: answers_datastore, frame: true, columns: [ {id: 'text', header: "Answer &amp;darr;", width: 500, sortable: true, dataIndex: 'text'}, {id: 'email', header: "Email", width: 300, sortable: true, dataIndex: 'email'} ], listeners: { rowdblclick: function(answersGrid, rowI, event) { Ext.MessageBox.show({ title: "Answer" , msg: "A", closable: true, autowidth: true }); } }, stripeRows: true, title:'Answers' }); </code></pre> <p>How to avoid duplication?</p>

2021

<p>From <a href="http://mitpress.mit.edu/sicp/full-text/book/book-Z-H-16.html" rel="nofollow">SICP</a>:</p> <blockquote> <p>Exercise 2.66. Implement the lookup procedure for the case where the set of records is structured as a binary tree, ordered by the numerical values of the keys.</p> </blockquote> <p>I wrote the following:</p> <pre><code>(define key car) (define make-record cons) (define value cadar) (define (lookup given-key set-of-records) (cond ((null? set-of-records) false) ((equal? given-key (key (car set-of-records))) (car set-of-records)) ((&lt; given-key (key (car set-of-records))) (lookup given-key (left-branch set-of-records))) (else (lookup given-key (right-branch set-of-records))))) </code></pre> <p>(The following part is from the book)</p> <pre><code>(define (entry tree) (car tree)) (define (left-branch tree) (cadr tree)) (define (right-branch tree) (caddr tree)) (define (make-tree entry left right) (list entry left right)) (define (list-&gt;tree elements) (car (partial-tree elements (length elements)))) (define (partial-tree elts n) (if (= n 0) (cons '() elts) (let ((left-size (quotient (- n 1) 2))) (let ((left-result (partial-tree elts left-size))) (let ((left-tree (car left-result)) (non-left-elts (cdr left-result)) (right-size (- n (+ left-size 1)))) (let ((this-entry (car non-left-elts)) (right-result (partial-tree (cdr non-left-elts) right-size))) (let ((right-tree (car right-result)) (remaining-elts (cdr right-result))) (cons (make-tree this-entry left-tree right-tree) remaining-elts)))))))) </code></pre> <p>How can my answer be improved?</p>

2024

<p>The <code>ConcurrentDictionary&lt;T,V&gt;</code> in .NET 4.0 is thread safe but not all methods are atomic.</p> <p><a href="http://msdn.microsoft.com/en-us/library/dd997369.aspx">This</a> points out that:</p> <blockquote> <p>... not all methods are atomic, specifically <code>GetOrAdd</code> and <code>AddOrUpdate</code>. The user delegate that is passed to these methods is invoked outside of the dictionary's internal lock.</p> </blockquote> <p><strong>Example Problem:</strong></p> <p>It is possible for the delegate method to be executed more than once for a given key.</p> <pre><code>public static readonly ConcurrentDictionary&lt;int, string&gt; store = new ConcurrentDictionary&lt;int, string&gt;(); [TestMethod] public void UnsafeConcurrentDictionaryTest() { Thread t1 = new Thread(() =&gt; { store.GetOrAdd(0, i =&gt; { string msg = "Hello from t1"; Trace.WriteLine(msg); Thread.SpinWait(10000); return msg; }); }); Thread t2 = new Thread(() =&gt; { store.GetOrAdd(0, i =&gt; { string msg = "Hello from t2"; Trace.WriteLine(msg); Thread.SpinWait(10000); return msg; }); }); t1.Start(); t2.Start(); t1.Join(); t2.Join(); } </code></pre> <p>The result shown in the Trace window shows "<strong>Hello from t1</strong>" and "<strong>Hello from t2</strong>". This is NOT the desired behavior for most implementations that we are using and confirms the problem noted in the MSDN link above. What we want is for only <em>one</em> of those delegates to be executed.</p> <p><strong>Proposed Solution:</strong></p> <p>I have to use the delegate overloads of these methods which led me to investigate this matter further. I stumbled onto <a href="http://kozmic.pl/2010/08/06/concurrentdictionary-in-net-4-not-what-you-would-expect/">this post</a> which suggests using the <code>Lazy&lt;T&gt;</code> class to ensure the delegate is only invoked once. With that in mind I wrote the following extension methods to mask the adding of a <code>Lazy&lt;T&gt;</code> wrapper to the value.</p> <pre><code>public static V GetOrAdd&lt;T, U, V&gt;(this ConcurrentDictionary&lt;T, U&gt; dictionary, T key, Func&lt;T, V&gt; valueFactory) where U : Lazy&lt;V&gt; { U lazy = dictionary.GetOrAdd(key, (U)new Lazy&lt;V&gt;(() =&gt; valueFactory(key))); return lazy.Value; } public static V AddOrUpdate&lt;T, U, V&gt;(this ConcurrentDictionary&lt;T, U&gt; dictionary, T key, Func&lt;T, V&gt; addValueFactory, Func&lt;T, V, V&gt; updateValueFactory) where U : Lazy&lt;V&gt; { U lazy = dictionary.AddOrUpdate(key, (U)new Lazy&lt;V&gt;(() =&gt; addValueFactory(key)), (k, oldValue) =&gt; (U)new Lazy&lt;V&gt;(() =&gt; updateValueFactory(k, oldValue.Value))); return lazy.Value; } </code></pre> <p><strong>Testing Solution:</strong></p> <p>Executing the same test above using a <code>ConcurrentDictionary</code> that has a Lazy value results in the value delegate ONLY being executed once (you either see "<strong>Hello from t1</strong>" or "<strong>Hello from t2</strong>")! </p> <pre><code>public static readonly ConcurrentDictionary&lt;int, Lazy&lt;string&gt;&gt; safeStore = new ConcurrentDictionary&lt;int, Lazy&lt;string&gt;&gt;(); </code></pre> <p>So it seems that this approach accomplished the goal.</p> <p>What do you think of this approach?</p>

2025

<p>I have two elements on my page:</p> <pre><code>&lt;ul id="VerticalMenu&gt;&lt;/ul&gt; &lt;ul id="AccordionMenu"&gt;&lt;/ul&gt; </code></pre> <p>I'm calling some JSON with jQuery and loading elements in the <code>div</code>s. I'm curious if there are things I can be doing more efficiently, and better ways to use selectors and JSON.</p> <pre><code>$().ready(function() { //Load sections GetCarlineSections(_BucketID); }); function GetCarlineSections(bucketID) { //Get section json list $.ajax( { type: "POST", url: _ApplicationRootURL + 'GetChildBucketList', //Call the ActionResult to return the JSON object data: 'parentID=' + bucketID, success: function (sections) { //'sections' is an array of JSON objects returned by GetChildBucketList $(sections).each(function () { $('#VerticalMenu') //Append each item to the #VerticalMenu &lt;ul&gt; .append( $('&lt;li/&gt;') //Append a new &lt;li&gt; element to &lt;ul&gt; #VerticalMenu .addClass('Section') .html( $('&lt;h4/&gt;') //Create a new &lt;h4&gt; inside of the &lt;li&gt; .addClass(this.BucketName) .html(this.BucketName) .click({ parentID: this.BucketID }, function (event) { //Attach a click event to the &lt;h4&gt; element $('#AccordionMenu').empty(); GetSectionSubSections(event.data.parentID); //Event.data.parentID is the id of the bucket represented by this &lt;h4&gt; element }) ) ); }); } }); } function GetSectionSubSections(bucketID) { $.ajax( { type: "POST", url: _ApplicationRootURL + 'GetChildBucketList', data: 'parentID=' + bucketID, success: function (SubSections) { //SubSections are the children buckets of Section, local var bucketID $(SubSections).each(function () { $('#AccordionMenu') .append( $('&lt;li/&gt;') .addClass('SubSection') .html( $('&lt;h4/&gt;') .addClass(this.SEOURLName) .html(this.BucketName) .click({ parentID: this.BucketID }, function (event) { //Eventdata parentID passes the SubSectionID to the event object GetSubSectionHeadlines(this, event.data.parentID) }) ) ); }); } }); } function GetSubSectionHeadlines(parentElement, SubSectionID) { //Get the Headlines based on the parent SubSection $(parentElement).after($('&lt;ul/&gt;').addClass(parentElement.className)); $.ajax({ type: 'POST', url: _ApplicationRootURL + 'GetChildBucketList', data: 'parentID=' + SubSectionID, success: function (Headlines) { $(Headlines).each(function () { $('ul.' + parentElement.className).prepend( $('&lt;li/&gt;') .html(this.BucketName) ) }) } }); } </code></pre>

2028

<p>This journey started with a quest to <a href="https://stackoverflow.com/questions/1297020/creating-the-shortest-possible-case-insensitive-verification-number">create the shortest possible case-insensitive verification number</a>. Based on the answers there, I worked out a <a href="https://stackoverflow.com/questions/1300846/classic-asp-vbscript-implementation-of-crawfords-base32-encoding">Classic ASP/VBScript implementation of Crockford's Base32 Encoding</a> and it has served me well so far.</p> <p>Out of semi-idle curiosity, I was wondering if there was a way to further improve the performance. To be clear: it works, and it runs more than fast enough. I am planning to use it more extensively and since I never heard back on a better way, I was hoping for a second set of eyes to say "yes, it's as good as it's going to get" or "here's how to make it more awesome" or whatever.</p> <p>So you don't have to go back to the latter Stack Overflow question to see the code, here it is:</p> <pre><code>'Base32 encoding functions for shorter, less confusing verification numbers Const kBase32Digits = "0123456789abcdefghjkmnpqrstvwxyz" Function ToBase32(ByVal lInput) Dim lModulo, sTemp Do Until lInput = 0 lModulo = lInput Mod 32 sTemp = Mid(kBase32Digits, lModulo + 1, 1) &amp; sTemp lInput = lInput \ 32 Loop ToBase32 = sTemp End Function Function FromBase32(ByVal sInput) Dim sTemp, sR, i,iY,lLen, zMultiplier sTemp = LCase(sInput) sTemp = Replace(sTemp,"o","0") sTemp = Replace(sTemp,"i","1") sTemp = Replace(sTemp,"l","1") sTemp = Replace(sTemp,"u","v") zMultiplier = 1 lLen = Len(sTemp) For i = lLen To 1 Step -1 sR = Mid(sTemp, i, 1) iY = InStr(1, kBase32Digits, sR, vbTextCompare) - 1 FromBase32 = FromBase32 + iY * zMultiplier zMultiplier = zMultiplier * 32 Next End Function </code></pre>

2029

<p>I don't have any questions about this piece of code; it compiles just fine in Visual Studio 2010. I just wanted to post it to see if anyone has any good ideas on how to simplify it, or pointing out any bad practices I have have done.</p> <pre><code>// Tic Tac Toe Game #include &lt;iostream&gt; #include &lt;iomanip&gt; using namespace std; class TicTacToe { private: char Board[3][3]; int play(); void playermove(); int turn(int); int check (int, int); void boardProgress(char x[][3]); int Winner(char x[][3]); int player1, player2, draw, player,winner,done; int row, col; public: int TG, T1, T2, TD; void intBoard(); int Stats(int); char playAgain(char); }playBall; int main() { playBall.TG = 0,playBall.T1 = 0,playBall.T2 = 0,playBall.TD = 0; int Winner = 0; // This will only display when the program is first run cout &lt;&lt; "You, are about to witness the program of the century.\n\n"; char done = false; while (!done) { // This will display before each game cout &lt;&lt; "COMMENCE TIC TAC TOE!!!!\n\n" "Ladies first, please pick the row then the column (1 through 3).\n\n"; // Play a game and remember who won (if anyone) playBall.intBoard(); //If you want to play again or not done = playBall.playAgain(done); } // Finish cout &lt;&lt; "\n\nThank you for playing!\n"; system ("pause"); return 0; } void TicTacToe::intBoard() { done = false; winner = 0; player = 2; player1 = 1; player2 = 2; draw = 3; int i,k; for (k=0;k&lt;3;k++) { for (i=0;i&lt;3;i++) { Board[k][i]=0; } } play(); } int TicTacToe::play() { int done = false; boardProgress(Board); while(!done) { playermove(); boardProgress(Board); done = Winner(Board); } Stats(winner); return 0; } void TicTacToe::playermove() { int answer = false; while (answer == false) { cout &lt;&lt;"Row: "; cin &gt;&gt; row; row--; cout &lt;&lt;"Colume: "; cin &gt;&gt; col; col--; answer = check(row,col); } player = turn(player); if (player == 1) Board[row][col] = 'X'; else if (player == 2) Board[row][col] = 'O'; else cout&lt;&lt; "Failed."; } int TicTacToe::check(int row, int col) { if(Board[row][col] == 0) { return true; } else if (Board[row][col] != 0) { cout &lt;&lt;"Can go there, Dude!\n\n"; return false; } else { cout&lt;&lt; "Going through Check"; Winner(Board); } return false; } int TicTacToe::turn(int player) { switch(player) { case 1: player = 2; { cout&lt;&lt;"\nPlayers 1 turn.\n\n"; break; } case 2: player = 1; { cout&lt;&lt;"\nPlayers 2 turn.\n\n"; break; } } return player; } int TicTacToe::Winner(char x[][3]) { winner = 0; int count = 0; int a = row; int b = col; for (a=0;a&lt;3;a++) { for (b=0;b&lt;3;b++) { if (Board[a][b]==0) { count++; } } } if (count &gt; 0) { int row, col, r, c, d, ro, co, dO; for (row=0; row&lt;3; row++) { r=0; ro=0; for (col=0; col&lt;3; col++) { if(x[row][col]=='X') r++; if(x[row][col]=='O') ro++; if (ro==3) { winner=2; } if (r==3) { winner=1; } } } for (col=0; col&lt;3; col++) { r=0; ro=0; for (row=0; row&lt;3; row++) { if(x[row][col]=='X') r++; if(x[row][col]=='O') ro++; if (ro==3) { winner=2; } if (r==3) { winner=1; } } } if (x[0][0]=='X' &amp;&amp; x[1][1]=='X' &amp;&amp; x[2][2]=='X') { winner=1; } else if (x[0][0]=='O' &amp;&amp; x[1][1]=='O' &amp;&amp; x[2][2]=='O') { winner=2; } else if (x[2][0]=='X' &amp;&amp; x[1][1]=='X' &amp;&amp; x[0][2]=='X') { winner=1; } else if (x[2][0]=='O' &amp;&amp; x[1][1]=='O' &amp;&amp; x[0][2]=='O') { winner=2; } } else if (count == 9) { cout &lt;&lt; "Its a draw, Bummer."; winner = 3; } else { cout&lt;&lt; "Next Player go, MEOW!\n\n"; } if (winner &gt; 0) { done = true; } return done; } int TicTacToe::Stats(int winner) { playBall.TG++; switch(winner) { case 1: T1++; { break; } case 2: T2++; { break; } case 3: TD++; { break; } } cout&lt;&lt;"You have played this many games: " &lt;&lt; TG; cout&lt;&lt;"\nPlayer1 won has won: " &lt;&lt; T1 &lt;&lt; " games."; cout&lt;&lt;"\nPlayer2 won has won: " &lt;&lt; T2 &lt;&lt; " games."; cout&lt;&lt;"\nYou have had: " &lt;&lt; TD &lt;&lt; " draws."; return 0; } char TicTacToe::playAgain(char done) { cout &lt;&lt;"\n\nWanna play again!?\n\n"; cout &lt;&lt;"Y/N: "; cin &gt;&gt; done; if(done == 'Y' || done == 'y') { done = false; } else { done = true; } return done; } void TicTacToe::boardProgress(char x[][3]) { cout &lt;&lt; " | | \n"; cout &lt;&lt; " " &lt;&lt; x[0][0] &lt;&lt; " | " &lt;&lt; x[0][1] &lt;&lt; " | " &lt;&lt; x[0][2] &lt;&lt;" \n"; cout &lt;&lt; " _____|_____|_____\n"; cout &lt;&lt; " | | \n"; cout &lt;&lt; " " &lt;&lt; x[1][0] &lt;&lt; " | " &lt;&lt; x[1][1] &lt;&lt; " | " &lt;&lt; x[1][2] &lt;&lt;" \n"; cout &lt;&lt; " _____|_____|_____\n"; cout &lt;&lt; " | | \n"; cout &lt;&lt; " " &lt;&lt; x[2][0] &lt;&lt; " | " &lt;&lt; x[2][1] &lt;&lt; " | " &lt;&lt; x[2][2] &lt;&lt;" \n"; cout &lt;&lt; " | | \n"; } </code></pre>

2032

<p>I've found this implementation on the web:</p> <blockquote> <pre><code>void insertSort(int a[], int length) { int i, j, value; int k=0; for(i = 1; i &lt; length; i++) { value = a[i]; for (j = i - 1; j &gt;= 0 &amp;&amp; a[j] &gt; value; j--) { a[j + 1] = a[j]; k++; } a[j+1] = value; } printf("k=%d", k); } </code></pre> </blockquote> <p>I have written this:</p> <pre><code>#include &lt;stdio.h&gt; #define SIZE 8 int array1[SIZE] = {77, 33, 44, 11, 88, 22, 66, 55}; void PrintArray() { int i = 0; printf("\n"); for(i=0 ; i&lt;SIZE ; i++) { printf("%d, ", array1[i]); } } void Insert(int insertPosition, int insertElementIndex) { int temp = array1[insertElementIndex]; int i = 0; for(i=insertElementIndex ; i&gt;=insertPosition ; i--) { array1[i] = array1[i-1]; } array1[insertPosition] = temp; } void InsertionSort() { int i = 0; int j = 0; int k = 0; for(i=0 ; i&lt;SIZE ; i++) { for(j=0 ; j&lt;=i ; j++) { if(array1[i] &lt; array1[j]) { Insert(j, i); PrintArray(); } k++; } } printf("k=%d", k); } main() { PrintArray(); InsertionSort(); //insertSort(array1, SIZE); PrintArray(); getch(); } </code></pre> <p>Is there any problem with this implementation?</p>

2034

<p>I want to split my helpers in different modules (and files), but I found some problems which I got around with the following solution:</p> <pre><code># app/helpers/application_helper.rb module ApplicationHelper include ApplicationContainer # ... end # app/helpers/partials/application_container.rb module ApplicationContainer # ... end </code></pre> <p>In particular at the beginning I was looking to have a file <code>/app/helpers/_application_container_helper.rb</code> that gave me <code>uninitialized constant ApplicationHelper::ApplicationContainer</code> (and different other errors playing around it), but right now I'm not even sure that makes sense. Any Idea or suggestions? </p>

2037

<p>This example comes from <a href="https://stackoverflow.com/questions/5761117/testing-if-colors-equal">a code snippet posted on Stack Overflow</a>:</p> <pre><code>private double brickVal(Color c) { if (c == Color.RED) { return 10.0; } else if (c == Color.ORANGE) { return 8.0; } else if (c == Color.YELLOW) { return 6.0; } else if (c == Color.GREEN) { return 4.0; } else if (c == Color.CYAN) { return 2.0; } else if (c == Color.MAGENTA) { return 1.0; } else { return 1.0; } } </code></pre> <p>Is the use of <code>==</code> here correct / best practice?</p>

2039

<pre><code>string s = Clipboard.GetText().Replace("\r", " "); string[] lines = s.Split('\n'); int row = dgView.CurrentCell.RowIndex; int col = dgView.CurrentCell.ColumnIndex; int linesCount = lines.Count(); if ((row + linesCount) - dgView.RowCount &gt; 0) dgView.Rows.Add((row + linesCount) - dgView.RowCount); asyncSqlResultsViewer.publicToolStripProgressBar.Maximum = linesCount; asyncSqlResultsViewer.publicToolStripProgressBar.Step = 1; asyncSqlResultsViewer.publicToolStripProgressBar.Visible = true; dgView.ReadOnly = true; foreach (string line in lines) { if (line.Length &gt; 0) { string[] cells = line.Split('\t'); for (int i = 0; i &lt; cells.GetLength(0); ++i) { if (col + i &lt; dgView.ColumnCount) { dgView[col + i, row].Value = cells[i]; } else { break; } } row++; } else { break; } asyncSqlResultsViewer.publicToolStripProgressBar.PerformStep(); } </code></pre> <p>It is ridiculously slow. Pasting 500 rows with 5 columns takes about 30 seconds. Please take into consideration that there might be already data in the <code>DataGridView</code> and I don't necessarily want to override it (it all depends on the starting cell). So I don't know how could I use a <code>DataTable</code> and assign it as <code>DataSource</code> in case you had that idea.</p>

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<p>From the text:</p> <blockquote> <p>Exercise 2.68. The encode procedure takes as arguments a message and a tree and produces the list of bits that gives the encoded message.</p> </blockquote> <pre><code>(define (encode message tree) (if (null? message) '() (append (encode-symbol (car message) tree) (encode (cdr message) tree)))) </code></pre> <blockquote> <p>Encode-symbol is a procedure, which you must write, that returns the list of bits that encodes a given symbol according to a given tree. You should design encode-symbol so that it signals an error if the symbol is not in the tree at all. Test your procedure by encoding the result you obtained in exercise 2.67 with the sample tree and seeing whether it is the same as the original sample message.</p> </blockquote> <p>The textbook provides the following definitions:</p> <pre><code>(define (make-leaf symbol weight) (list 'leaf symbol weight)) (define (leaf? object) (eq? (car object) 'leaf)) (define (symbol-leaf x) (cadr x)) (define (weight-leaf x) (caddr x)) (define (make-code-tree left right) (list left right (append (symbols left) (symbols right)) (+ (weight left) (weight right)))) (define (left-branch tree) (car tree)) (define (right-branch tree) (cadr tree)) (define (symbols tree) (if (leaf? tree) (list (symbol-leaf tree)) (caddr tree))) (define (weight tree) (if (leaf? tree) (weight-leaf tree) (cadddr tree))) (define (decode bits tree) (define (decode-1 bits current-branch) (if (null? bits) '() (let ((next-branch (choose-branch (car bits) current-branch))) (if (leaf? next-branch) (cons (symbol-leaf next-branch) (decode-1 (cdr bits) tree)) (decode-1 (cdr bits) next-branch))))) (decode-1 bits tree)) (define (choose-branch bit branch) (cond ((= bit 0) (left-branch branch)) ((= bit 1) (right-branch branch)) (else (error "bad bit -- CHOOSE-BRANCH" bit)))) (define (adjoin-set x set) (cond ((null? set) (list x)) ((&lt; (weight x) (weight (car set))) (cons x set)) (else (cons (car set) (adjoin-set x (cdr set)))))) (define (make-leaf-set pairs) (if (null? pairs) '() (let ((pair (car pairs))) (adjoin-set (make-leaf (car pair) ; symbol (cadr pair)) ; frequency (make-leaf-set (cdr pairs)))))) (define sample-tree (make-code-tree (make-leaf 'A 4) (make-code-tree (make-leaf 'B 2) (make-code-tree (make-leaf 'D 1) (make-leaf 'C 1))))) (define sample-message '(0 1 1 0 0 1 0 1 0 1 1 1 0)) (define (encode message tree) (if (null? message) '() (append (encode-symbol (car message) tree) (encode (cdr message) tree)))) </code></pre> <p>And I wrote the following answer:</p> <pre><code>(define (member? x set) (not (equal? (member x set) false))) (define (encode-branch symbol tree) (let ((left (left-branch tree)) (right (right-branch tree))) (cond ((member? symbol (symbols left)) (list 0 left)) ((member? symbol (symbols right)) (list 1 right)) (else (error "Symbol is not a member of either left or right branches of the tree - can't encode" symbol tree))))) (define (encode-symbol symbol tree) (if (leaf? tree) '() (let ((new-branch (encode-branch symbol tree))) (cons (car new-branch) (encode-symbol symbol (cadr new-branch)))))) </code></pre> <p>How can I improve my solution?</p>

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<p>From <a href="http://mitpress.mit.edu/sicp/full-text/book/book-Z-H-16.html#%_thm_2.69" rel="nofollow">SICP</a>:</p> <blockquote> <p>Exercise 2.69. The following procedure takes as its argument a list of symbol-frequency pairs (where no symbol appears in more than one pair) and generates a Huffman encoding tree according to the Huffman algorithm.</p> <pre><code>(define (generate-huffman-tree pairs) (successive-merge (make-leaf-set pairs))) </code></pre> <p>Make-leaf-set is the procedure given above that transforms the list of pairs into an ordered set of leaves. Successive-merge is the procedure you must write, using make-code-tree to successively merge the smallest-weight elements of the set until there is only one element left, which is the desired Huffman tree. (This procedure is slightly tricky, but not really complicated. If you find yourself designing a complex procedure, then you are almost certainly doing something wrong. You can take significant advantage of the fact that we are using an ordered set representation.)</p> </blockquote> <p>I wrote the following solution:</p> <pre><code>(define (generate-huffman-tree pairs) (successive-merge (make-leaf-set pairs))) (define (successive-merge leaf-set) (define (iter result leaf-subset) (if (null? leaf-subset) result (let ((first-leaf (car leaf-subset))) (iter (make-code-tree first-leaf result) (cdr leaf-subset))))) (iter (make-code-tree (car leaf-set) (cadr leaf-set)) (cddr leaf-set))) </code></pre> <p>Is this a good answer? Can it be improved?</p>

2046

<p>What would be a prettier/faster way to do handling of multiple errors in Ruby? Here is the code I am working with:</p> <pre><code>begin response = session.get url rescue Patron::HostResolutionError puts "Error resolving remote host." exit 1 rescue Patron::PartialFileError puts "File size mismatch. (Host reported a file size, but the actual file is of different size)" exit 1 rescue Patron::TimeoutError puts "Operation timed out." exit 1 rescue Patron::TooManyRedirects puts "Tried redirecting too many times." exit 1 rescue Patron::URLFormatError puts "Error with the URL format" exit 1 rescue Patron::UnsupportedProtocol puts "This URL is using a protocol that we cannot handle." exit 1 rescue Patron::ConnectionFailed puts "Error connecting to host. Check your internet connection." exit 1 end </code></pre>

2049

<p>The <a href="http://en.wikipedia.org/wiki/Tiny_Encryption_Algorithm" rel="noreferrer">TEA</a> is a very simple encryption algorithm requiring little time and space - perfect for embedded systems. There are extensions to it, and every version has its flaws (WEP was based on it), but for casual protection it's perfect.</p> <p>Also, the encrypt and decrypt routines are exactly as found from Wikipedia, so I don't expect anyone to check that I'm following the TEA correctly - I'm more interested in the block routines I've added, though if you notice something about the TEA routines it would be good to know.</p> <p><strong>tea.h</strong></p> <pre><code>#ifndef __TEA.H__ #define __TEA.H__ #include &lt;stdint.h&gt; void encrypt (uint32_t* v, uint32_t* k); void decrypt (uint32_t* v, uint32_t* k); void encryptBlock(uint8_t * data, uint32_t * len, uint32_t * key); void decryptBlock(uint8_t * data, uint32_t * len, uint32_t * key); #endif </code></pre> <p><strong>tea.c</strong></p> <pre><code>#include "tea.h" /* encryptBlock * Encrypts byte array data of length len with key key using TEA * Arguments: * data - pointer to 8 bit data array to be encrypted - SEE NOTES * len - length of array * key - Pointer to four integer array (16 bytes) holding TEA key * Returns: * data - encrypted data held here * len - size of the new data array * Side effects: * Modifies data and len * NOTES: * data size must be equal to or larger than ((len + 7) / 8) * 8 + 8 * TEA encrypts in 8 byte blocks, so it must include enough space to * hold the entire data to pad out to an 8 byte boundary, plus another * 8 bytes at the end to give the length to the decrypt algorithm. * * - Shortcut - make sure that data is at least len + 15 bytes in size. */ void encryptBlock(uint8_t * data, uint32_t * len, uint32_t * key) { uint32_t blocks, i; uint32_t * data32; // treat the data as 32 bit unsigned integers data32 = (uint32_t *) data; // Find the number of 8 byte blocks, add one for the length blocks = (((*len) + 7) / 8) + 1; // Set the last block to the original data length data32[(blocks*2) - 1] = *len; // Set the encrypted data length *len = blocks * 8; for(i = 0; i&lt; blocks; i++) { encrypt(&amp;data32[i*2], key); } } /* decryptBlock * Decrypts byte array data of length len with key key using TEA * Arguments: * data - pointer to 8 bit data array to be decrypted - SEE NOTES * len - length of array * key - Pointer to four integer array (16 bytes) holding TEA key * Returns: * data - decrypted data held here * len - size of the new data array * Side effects: * Modifies data and len * NOTES: * None */ void decryptBlock(uint8_t * data, uint32_t * len, uint32_t * key) { uint32_t blocks, i; uint32_t * data32; // treat the data as 32 bit unsigned integers data32 = (uint32_t *) data; // Find the number of 8 byte blocks blocks = (*len)/8; for(i = 0; i&lt; blocks; i++) { decrypt(&amp;data32[i*2], key); } // Return the length of the original data *len = data32[(blocks*2) - 1]; } /* encrypt * Encrypt 64 bits with a 128 bit key using TEA * From http://en.wikipedia.org/wiki/Tiny_Encryption_Algorithm * Arguments: * v - array of two 32 bit uints to be encoded in place * k - array of four 32 bit uints to act as key * Returns: * v - encrypted result * Side effects: * None */ void encrypt (uint32_t* v, uint32_t* k) { uint32_t v0=v[0], v1=v[1], sum=0, i; /* set up */ uint32_t delta=0x9e3779b9; /* a key schedule constant */ uint32_t k0=k[0], k1=k[1], k2=k[2], k3=k[3]; /* cache key */ for (i=0; i &lt; 32; i++) { /* basic cycle start */ sum += delta; v0 += ((v1&lt;&lt;4) + k0) ^ (v1 + sum) ^ ((v1&gt;&gt;5) + k1); v1 += ((v0&lt;&lt;4) + k2) ^ (v0 + sum) ^ ((v0&gt;&gt;5) + k3); } /* end cycle */ v[0]=v0; v[1]=v1; } /* decrypt * Decrypt 64 bits with a 128 bit key using TEA * From http://en.wikipedia.org/wiki/Tiny_Encryption_Algorithm * Arguments: * v - array of two 32 bit uints to be decoded in place * k - array of four 32 bit uints to act as key * Returns: * v - decrypted result * Side effects: * None */ void decrypt (uint32_t* v, uint32_t* k) { uint32_t v0=v[0], v1=v[1], sum=0xC6EF3720, i; /* set up */ uint32_t delta=0x9e3779b9; /* a key schedule constant */ uint32_t k0=k[0], k1=k[1], k2=k[2], k3=k[3]; /* cache key */ for (i=0; i&lt;32; i++) { /* basic cycle start */ v1 -= ((v0&lt;&lt;4) + k2) ^ (v0 + sum) ^ ((v0&gt;&gt;5) + k3); v0 -= ((v1&lt;&lt;4) + k0) ^ (v1 + sum) ^ ((v1&gt;&gt;5) + k1); sum -= delta; } /* end cycle */ v[0]=v0; v[1]=v1; } </code></pre> <p><strong>Issues so far:</strong></p> <p><strong>Coding</strong></p> <ul> <li>Using <a href="https://stackoverflow.com/questions/47882/what-is-a-magic-number-and-why-is-it-bad">magic numbers</a> in encrypt and decrypt routines - use #defines instead - Kyle</li> <li>If the 64 bit encoding functions aren't used outside this module, their prototypes should be in the code, not header - Simon</li> <li>Add sanity checking to input - Rob</li> <li>Require that input len is a multiple of 8 bytes - making a requirement we can't enforce or check is a recipe for corruption - Rob</li> </ul> <p><strong>Style</strong></p> <ul> <li>Using K&amp;R brace style in some places, ANSI in others - consistency - Simon</li> <li>The long descriptive comment is more useful for the end user if it's in the header file (Header for usage, code for implementation) - Rob</li> </ul> <hr> <p><strong>EDIT:</strong></p> <p>Someone asked for the implementation I indicated in the original post, so here it is. Note that I've not cleaned it up for presentation.</p> <p>To decode a file use <code>decode inputfilename outputfilename</code>. To encode a file use <code>decode inputfilename outputfilename e</code>. ANSI C implementation, so it should work anywhere, although the algorithm itself might be endian dependant.</p> <p>THE DECRYPTED FILE WILL NOT EXACTLY MATCH THE ORIGINAL FILE. This particular implementation leaves a number of null bytes on the end of the decrypted file that were not present in the original. For my application this was acceptable and simplified my particular usage, but you are likely going to need to modify this for your use.</p> <p>It uses a fixed key on line 4.</p> <pre><code>#include &lt;stdio.h&gt; typedef unsigned long uint32_t; const uint32_t TEAKey[4] = {0x95a8882c, 0x9d2cc113, 0x815aa0cd, 0xa1c489f7}; void encrypt (uint32_t* v, const uint32_t* k); void decrypt (uint32_t* v, const uint32_t* k); void btea(uint32_t *v, int n, uint32_t const k[4]); void simpleencrypt(unsigned char * buffer); void simpledecrypt(unsigned char * buffer); int main(int argc, char **argv) { FILE *fpin, *fpout; int bytecount; unsigned char buffer[9], bufferin[9], bufferout[9]; int i; if(argc &lt; 3) { printf("Use: %s [filenameinput] [filenameoutput]\n", argv[0]); return 0; } if( (fpin = fopen(argv[1], "rb")) == NULL) { printf("Problem opening input file %s.\n", argv[1]); return 0; } if( (fpout = fopen(argv[2], "wb")) == NULL) { printf("Problem opening output file %s.\n", argv[2]); return 0; } bytecount = 0; while(fread(buffer, 1, 8, fpin) == 8) { if(argc&gt;3) { for(i=0;i&lt;8;i++) { bufferin[i] = buffer[i]; } simpleencrypt(buffer); for(i=0;i&lt;8;i++) { bufferout[i] = buffer[i]; } simpledecrypt(bufferout); for(i=0;i&lt;8;i++) { if(bufferin[i] != bufferout[i]) { printf("Internal decode test failed.\n"); } } } else { simpledecrypt(buffer); } fwrite(buffer, 1, 8, fpout); bytecount+=8; } if (!feof(fpin)) { printf("Unexpected input file error encountered.\n"); } fclose(fpin); fclose(fpout); printf("%s complete, %i bytes total\n",((argc&gt;3) ? "Encrypt" : "Decrypt"), bytecount); return 0; } void simpleencrypt(unsigned char * buffer) { uint32_t datablock[2]; datablock[0] = (buffer[0] &lt;&lt; 24) | (buffer[1] &lt;&lt; 16) | (buffer[2] &lt;&lt; 8) | (buffer[3]); datablock[1] = (buffer[4] &lt;&lt; 24) | (buffer[5] &lt;&lt; 16) | (buffer[6] &lt;&lt; 8) | (buffer[7]); encrypt (datablock, TEAKey); buffer[0] = (char) ((datablock[0] &gt;&gt; 24) &amp; 0xFF); buffer[1] = (char) ((datablock[0] &gt;&gt; 16) &amp; 0xFF); buffer[2] = (char) ((datablock[0] &gt;&gt; 8) &amp; 0xFF); buffer[3] = (char) ((datablock[0]) &amp; 0xFF); buffer[4] = (char) ((datablock[1] &gt;&gt; 24) &amp; 0xFF); buffer[5] = (char) ((datablock[1] &gt;&gt; 16) &amp; 0xFF); buffer[6] = (char) ((datablock[1] &gt;&gt; 8) &amp; 0xFF); buffer[7] = (char) ((datablock[1]) &amp; 0xFF); } void simpledecrypt(unsigned char * buffer) { uint32_t datablock[2]; datablock[0] = (buffer[0] &lt;&lt; 24) | (buffer[1] &lt;&lt; 16) | (buffer[2] &lt;&lt; 8) | (buffer[3]); datablock[1] = (buffer[4] &lt;&lt; 24) | (buffer[5] &lt;&lt; 16) | (buffer[6] &lt;&lt; 8) | (buffer[7]); decrypt (datablock, TEAKey); buffer[0] = (char) ((datablock[0] &gt;&gt; 24) &amp; 0xFF); buffer[1] = (char) ((datablock[0] &gt;&gt; 16) &amp; 0xFF); buffer[2] = (char) ((datablock[0] &gt;&gt; 8) &amp; 0xFF); buffer[3] = (char) ((datablock[0]) &amp; 0xFF); buffer[4] = (char) ((datablock[1] &gt;&gt; 24) &amp; 0xFF); buffer[5] = (char) ((datablock[1] &gt;&gt; 16) &amp; 0xFF); buffer[6] = (char) ((datablock[1] &gt;&gt; 8) &amp; 0xFF); buffer[7] = (char) ((datablock[1]) &amp; 0xFF); } /* encrypt * Encrypt 64 bits with a 128 bit key using TEA * From http://en.wikipedia.org/wiki/Tiny_Encryption_Algorithm * Arguments: * v - array of two 32 bit uints to be encoded in place * k - array of four 32 bit uints to act as key * Returns: * v - encrypted result * Side effects: * None */ void encrypt (uint32_t* v, const uint32_t* k) { uint32_t v0=v[0], v1=v[1], sum=0, i; /* set up */ uint32_t delta=0x9e3779b9; /* a key schedule constant */ uint32_t k0=k[0], k1=k[1], k2=k[2], k3=k[3]; /* cache key */ for (i=0; i &lt; 32; i++) { /* basic cycle start */ sum += delta; v0 += ((v1&lt;&lt;4) + k0) ^ (v1 + sum) ^ ((v1&gt;&gt;5) + k1); v1 += ((v0&lt;&lt;4) + k2) ^ (v0 + sum) ^ ((v0&gt;&gt;5) + k3); } /* end cycle */ v[0]=v0; v[1]=v1; } /* decrypt * Decrypt 64 bits with a 128 bit key using TEA * From http://en.wikipedia.org/wiki/Tiny_Encryption_Algorithm * Arguments: * v - array of two 32 bit uints to be decoded in place * k - array of four 32 bit uints to act as key * Returns: * v - decrypted result * Side effects: * None */ void decrypt (uint32_t* v, const uint32_t* k) { uint32_t v0=v[0], v1=v[1], sum=0xC6EF3720, i; /* set up */ uint32_t delta=0x9e3779b9; /* a key schedule constant */ uint32_t k0=k[0], k1=k[1], k2=k[2], k3=k[3]; /* cache key */ for (i=0; i&lt;32; i++) { /* basic cycle start */ v1 -= ((v0&lt;&lt;4) + k2) ^ (v0 + sum) ^ ((v0&gt;&gt;5) + k3); v0 -= ((v1&lt;&lt;4) + k0) ^ (v1 + sum) ^ ((v1&gt;&gt;5) + k1); sum -= delta; } /* end cycle */ v[0]=v0; v[1]=v1; } #define DELTA 0x9e3779b9 #define MX ((z&gt;&gt;5^y&lt;&lt;2) + (y&gt;&gt;3^z&lt;&lt;4)) ^ ((sum^y) + (k[(p&amp;3)^e] ^ z)); void btea(uint32_t *v, int n, uint32_t const k[4]) { uint32_t y, z, sum; unsigned p, rounds, e; if (n &gt; 1) { /* Coding Part */ rounds = 6 + 52/n; sum = 0; z = v[n-1]; do { sum += DELTA; e = (sum &gt;&gt; 2) &amp; 3; for (p=0; p&lt;n-1; p++) y = v[p+1], z = v[p] += MX; y = v[0]; z = v[n-1] += MX; } while (--rounds); } else if (n &lt; -1) { /* Decoding Part */ n = -n; rounds = 6 + 52/n; sum = rounds*DELTA; y = v[0]; do { e = (sum &gt;&gt; 2) &amp; 3; for (p=n-1; p&gt;0; p--) z = v[p-1], y = v[p] -= MX; z = v[n-1]; y = v[0] -= MX; } while ((sum -= DELTA) != 0); } } </code></pre>

2050

<p>5 years ago, when i was in love with <code>VB</code>, I created this simple program to detect if a file is virus or not.</p> <p>What I'd like is to see if you can help me optimize it, speed-wise.</p> <p>I open an executable file in a rich textbox control and use the <code>Instr</code> method to search for occurrences of predefined string. The problem is that the <code>Instr</code> method is damn slow when searching files as small as 512KB.</p> <p>Can the speed be enhanced?</p> <pre><code>If InStr(1, rt.Text, "scripting.filesystemobject") Then It does something with FSO End If If InStr(1, rt.Text, "thisprogramcannotberunindosmode") Or InStr(1, rt.Text, "thisprogrammustberununderwin32") Then Probably a DOS program Else looks like a GUI program End If If InStr(1, rt.Text, "hkey_local_machine") Then Does something with registry End If If InStr(1, rt.Text, "hkey_users") Then Does something with registry End If If InStr(1, rt.Text, "hkey_current_user") Then Does something with registry End If If InStr(1, rt.Text, "hkey_classes_root") Then Does something with registry End If If InStr(1, rt.Text, "hkey_current_config") Then Does something with registry End If </code></pre>

2059

<p>In my nested <code>for</code> loops below, it is sometimes necessary to exit the outer loop and then continue program execution. Since loop labels and other goto-like constructions are heavily discouraged, I'm a bit afraid of raptors. Is this usage OK? Is there a better way to structure the program?</p> <pre><code>my @objects = load_objects(); OUTER: for my $obj ( @objects ) { for my $element ( @{$obj-&gt;elements} ) { if ( is_case_1( $element ) ) { ... } elsif ( is_case_2( $element ) ) { ... } else { warn "invalid element: $element"; last OUTER; } stuff_that_assumes_valid_element( $element ); } stuff_that_assumes_valid_object( $obj ); } store_objects( @objects ); </code></pre>

2060

<p>I am new to Rails and have a system that needs to process transactions.</p> <p>A user can enter a transaction to which one or more users are tied. These users owe some amount of money to the person making the transaction. For example, Bill might buy lunch for 4 friends and the bill is $125. They decide to split the bill 5 ways, so each owes $25. Bill would enter a total of $125 and enter each friend (including himself) as owing $25 to the transaction.</p> <p>I have code in my controller and in my model to accomplish this goal, but I don't really know if I am using transactions and locking correctly. Also, is this the intended way to have this information in the controller?</p> <p>I am using a transaction since all of these actions must occur together or fail (atomicity) and I need locking in case multiple users try to submit at the same time (isolation).</p> <p>Maybe I should let the db on the backend handle locking? Does it do that already - say, MySQL?</p> <p><strong>trans_controller.rb</strong></p> <pre><code>class TransController &lt; ApplicationController # POST trans/ def create @title = "Create Transaction" trans_successful = false # Add the transaction from the client @tran = Tran.new(params[:tran]) # Update the current user @tran.submitting_user_id = current_user.id # Update the data to the database # This call commits the transaction and transaction users # It also calls a method to update the balances of each user since that isn't # part of the regular commit (why isn't it?) begin @tran.transaction do @tran.save! @tran.update_user_balances trans_successful = true end rescue end # Save the transaction if trans_successful flash[:success] = 'Transaction was successfully created.' redirect_to trans_path else flash.now[:error] = @tran.errors.full_messages.to_sentence render 'new' end end </code></pre> <p><strong>tran.rb</strong></p> <pre><code>class Tran &lt; ActiveRecord::Base has_many :transaction_users, :dependent =&gt; :destroy, :class_name =&gt; 'TransactionUser' belongs_to :submitting_user, :class_name =&gt; 'User' belongs_to :buying_user, :class_name =&gt; 'User' accepts_nested_attributes_for :transaction_users, :allow_destroy =&gt; true validates :description, :presence =&gt; true, :length =&gt; {:maximum =&gt; 100 } #validates :total, :presence =&gt; true validates_numericality_of :total, :greater_than =&gt; 0 validates :submitting_user_id, :presence =&gt; true validates :buying_user_id, :presence =&gt; true #validates_associated :transaction_users validate :has_transaction_users? validate :has_correct_transaction_user_sum? validate :has_no_repeat_users? def update_user_balances # Update the buying user in the transaction self.buying_user.lock! # Update the user's total, since they were in the transction self.buying_user.update_attribute :current_balance, self.buying_user.current_balance - self.total # Add an offsetting transaction_user for this record buying_tran_user = TransactionUser.create!(:amount =&gt; -1 * self.total, :user_id =&gt; self.buying_user_id, :tran =&gt; self) #if buying_tran_user.valid? # raise "Error" #end # Loop through each transaction user and update their balances. Make sure to lock each record before doing the update. self.transaction_users.each do |tu| tu.user.lock! tu.user.update_attribute :current_balance, tu.user.current_balance + tu.amount end end def has_transaction_users? errors.add :base, "A transcation must have transaction users." if self.transaction_users.blank? end def has_correct_transaction_user_sum? sum_of_items = 0; self.transaction_users.inspect self.transaction_users.each do |key| sum_of_items += key.amount if !key.amount.nil? end if sum_of_items != self.total errors.add :base, "The transcation items do not sum to the total of the transaction." end end def has_no_repeat_users? user_array = [] self.transaction_users.each do |key| if(user_array.include? key.user.email) errors.add :base, "The participant #{key.user.full_name} has been listed more than once." end user_array &lt;&lt; key.user.email end end end </code></pre>

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<p>My friend does a bunch of Java work (commandline, still toying around) and I notice a bunch of try/catch blocks like this:</p> <pre><code> try { double a = Double.parseDouble(secondInput); } catch(NumberFormatException nFE) { System.out.println("The input was not an integer."); try { Thread.sleep(1997); } catch (InterruptedException e) { // TODO Auto-generated catch block e.printStackTrace(); } System.exit(0); } </code></pre> <p>Which, IMO doesn't look very pretty. And I'm wondering what the "better" way to write this code would be.</p>

2076

<p>I have a simple quantity display function that runs for every product displayed in our catalog. The <code>MaxQtyDisplay</code> value is set in our web.config file. Part of me thinks the function is as streamlined as possible and part of me thinks it can be improved upon somewhere. Because this function is called many, many times in our web application I would like it be optimized as best it could.</p> <p>What could be done to improve it?</p> <pre><code>Private Shared Function CalculateQtyDisplay(ByVal x As Double, ByVal y As Double) As Double Dim q As Double = x - y If q &gt; 0 And q &lt;= My.Settings.MaxQtyDisplay Then Return q ElseIf q &gt; My.Settings.MaxQtyDisplay Then Return My.Settings.MaxQtyDisplay Else Return 0 End If End Function </code></pre>

2093

<p>This is a jQuery plug-in I've created that relies on jQuery UI's tabs plug-in. It adds some framework specific logic when setting up tabs:</p> <ol> <li>Fixes a bug in jQuery that appears when an id/class contains a "."</li> <li>Manages the tab state using a framework specific cookie API (does not use the jQuery cookie plugin)</li> <li>Exposes a couple of options for transition behavior</li> </ol> <p>I'd love to get some suggestions on how to improve this, as it'll be used widely in the framework.</p> <pre><code>(function ($) { $.fn.dnnTabs = function (options) { var opts = $.extend({}, $.fn.dnnTabs.defaultOptions, options), $wrap = this; $(document).ready(function () { // Patch for Period in IDs (jQuery bug) $.ui.tabs.prototype._sanitizeSelector = function (hash) { // we need this because an id may contain a ":" or a '.' return hash.replace(/:/g, "\\:").replace(/\./g, "\\\."); }; var id = 'dnnTabs-' + $wrap.selector.replace('#', '').replace('.', ''); if (opts.selected === -1) { var tabCookie = dnn.dom.getCookie(id); if (tabCookie) { opts.selected = tabCookie; } if (opts.selected === -1) { opts.selected = 0; } } $wrap.tabs({ show: function (event, ui) { dnn.dom.setCookie(id, ui.index, 1, '/', '', false); }, selected: opts.selected, fx: { opacity: opts.opacity, duration: opts.duration } }); }); return $wrap; }; $.fn.dnnTabs.defaultOptions = { opacity: 'toggle', duration: 'fast', selected: -1 }; })(jQuery); </code></pre>

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<p>I am new to the world of coding as well as XHTML and PHP. As a way to gain more experience as well as to put theory into practice including a way to challenge myself, I put together the following code that calculates values a user enters into a form. </p> <p>This was to test my knowledge regarding PHP's own functions but also creating custom functions. I am sure the code can be improved and would appreciate any advise. </p> <p>The one thing I was unable to do was to only display the result and to hide the form once it has been posted preferably on the same page i.e. not redirecting the user to another page.</p> <p>I have also tried to keep business logic and presentation as much as possible.</p> <p><em>Appreciate any advise as well as constructive criticism.</em></p> <p><strong>Main Page Code - Calculator.php</strong></p> <pre><code>&lt;?php require_once('includes/base.php'); require_once('functions.php'); ?&gt; &lt;!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"&gt; &lt;html&gt; &lt;head&gt; &lt;title&gt;Calculator&lt;/title&gt; &lt;/head&gt; &lt;body&gt; &lt;h1&gt;Calculator Instructions&lt;/h1&gt; &lt;p&gt;Below are instructions on using the calculator&lt;/p&gt; &lt;ol&gt; &lt;li&gt;You must specify 2 values in the fields below&lt;/li&gt; &lt;li&gt;You must select an arithmetic operator which includes the list below &lt;ul&gt; &lt;li&gt;Multiply&lt;/li&gt; &lt;li&gt;Divide&lt;/li&gt; &lt;li&gt;Modulus&lt;/li&gt; &lt;li&gt;Add&lt;/li&gt; &lt;li&gt;Subtract&lt;/li&gt; &lt;/ul&gt; &lt;/li&gt; &lt;li&gt;Simply submit the form once you have specified 2 values and selected arithmetic operator&lt;/li&gt; &lt;/ol&gt; &lt;h2&gt;Calculator&lt;/h2&gt; &lt;div&gt; &lt;?php if(isset($_POST['submit'])) { echo mycalculator(); } ?&gt; &lt;/div&gt; &lt;form name="calculator" method="post" action="calculator.php"&gt; &lt;div&gt; Field 1: &lt;br /&gt; &lt;input type="input" name="field1" value="&lt;?php if(isset($_POST['field1'])) { echo $_POST['field1']; } ?&gt;" /&gt; &lt;/div&gt; &lt;div&gt; Field 2: &lt;br /&gt; &lt;input type="input" name="field2" value="&lt;?php if(isset($_POST['field2'])) { echo $_POST['field2']; } ?&gt;" /&gt; &lt;/div&gt; &lt;div&gt; Select an arithmetic operator: &lt;br /&gt; &lt;select name="field3"&gt; &lt;option value=""&gt;Please select an option&lt;/option&gt; &lt;?php echo myselect(); ?&gt; &lt;/select&gt; &lt;/div&gt; &lt;div&gt; &lt;/div&gt; &lt;div&gt; &lt;input type="submit" name="submit" value="submit" /&gt; &lt;input type="reset" name="reset" value="reset" /&gt; &lt;/div&gt; &lt;/form&gt; &lt;/body&gt; &lt;/html&gt; </code></pre> <p><strong>Define and Set directory and path - Base.php</strong></p> <pre><code>&lt;?php //Retrieve parent directory $parentdirectory = dirname(dirname(__FILE__)); $unixpath = str_replace('\\', '/', $parentdirectory); //Define root directory define('BASE_DIRECTORY', $parentdirectory); //Set includes directory ini_set('include_path', $parentdirectory.'\includes'); ?&gt; </code></pre> <p><strong>Business Logic - Functions.php</strong></p> <pre><code>&lt;?php //Generate arithmetic menu function myselect () { //Define arithmetic operators $selectarray = array('multiply', 'divide', 'modulus', 'add', 'subtract'); $status = ''; foreach($selectarray as $seletkey =&gt; $selectvalue) { if($_POST['field3'] == $selectvalue) { $status = 'selected'; } else { $status = ''; } echo '&lt;option value="'.$selectvalue.'" '.$status.'&gt;'.$selectvalue.'&lt;/option&gt;'; } } //Validate if form has been submitted if(isset($_POST['submit'])) { //Generate errors if form is not completed function mycalculator() { //Instatiate form fields, error messages and arithmetic operators $formfields = array('a' =&gt; 'field1', 'b' =&gt; 'field2', 'c' =&gt; 'field3'); // $formfieldkeys = array_values($formfields); $formfieldkeys = array_combine(range(1, count($formfields)), array_values($formfields)); //Instantiate error messages array $errormsg = array(); //Validate if form field has been set foreach($formfieldkeys as $formfieldkey =&gt; $formfieldvalue) { $formfield = isset($_POST[$formfieldvalue]) ? $_POST[$formfieldvalue] : ''; //Return error message if(empty($formfield)) { $errormsg = 'Please specify a value for field '.$formfieldkey.'&lt;br /&gt;'; /* Return error message for the specific field concerned using array_values $errormsg = 'Please specify a value for field '.($formfieldkey + 1).'&lt;br /&gt;'; */ echo $errormsg; } //Validate if the values being posted for fields 1 - 2 are numeric if(in_array($formfieldvalue, array('field1','field2'))) { if(!is_numeric($formfield)) { $errormsg = 'You must provide a numeric value for field '.$formfieldkey.'&lt;br /&gt;'; /* Return error message for the specific field concerned using array_values $errormsg = 'You must provide a numeric value for field '.($formfieldkey + 1).'&lt;br /&gt;'; */ echo $errormsg; } } if(!empty($formfield)) { //Extract individual array values // extract($formfields); // $field1 = $_POST[$a]; // $field2 = $_POST[$b]; // $field3 = $_POST[$c]; //Dynamic Variables ${"field{$formfieldkey}"} = $_POST[$formfieldvalue]; if(!empty($field1) &amp;&amp; !empty($field2) &amp;&amp; !empty($field3)) { if($field3 == 'multiply') { $calculate = $field1 * $field2; // echo $calculate; } elseif($field3 == 'divide') { $calculate = $field1 / $field2; // echo $calculate; } elseif($field3 == 'modulus') { $calculate = $field1 % $field2; // echo $calculate; } elseif($field3 == 'add') { $calculate = $field1 + $field2; // echo $calculate; } elseif($field3 == 'subtract') { $calculate = $field1 - $field2; // echo $calculate; } else { $calculate = 'error'; } if($calculate &gt; 0) { return 'The answer is '.$calculate; } } } } } //Debug // print_r($_POST); } ?&gt; </code></pre>

2097

<p><strong>Edit:</strong></p> <p>The purpose of this method is to search a specific directory for a given file type, ex. (*.txt, *.pdb, *.exe") then move the file(s) to a given destination directory and delete the original file from the source directory.</p> <p>Is there a better way to write the following code?:</p> <pre><code>/// &lt;summary&gt; /// Moves a specific file type from a given /// source directory to a destination directory. /// &lt;/summary&gt; /// &lt;param name="sourceDir"&gt;The source directory.&lt;/param&gt; /// &lt;param name="destDir"&gt;The destination directory.&lt;/param&gt; /// &lt;param name="fileExt"&gt;Type of file to be moved.&lt;/param&gt; private static void MoveFilesToDirectory(string sourceDir, string destDir, string fileExt) { try { if ( !Directory.Exists(sourceDir) ) { Console.WriteLine("{0} does not exist.", sourceDir); return; } if ( !Directory.Exists(destDir) ) { Directory.CreateDirectory(destDir); } foreach ( String dir in Directory.GetDirectories(sourceDir) ) { foreach ( String file in Directory.GetFiles(dir, fileExt) ) { string fileName = Path.GetFileName(file); string moveFileTo = Path.Combine(destDir, fileName); if ( !File.Exists(moveFileTo) ) { Directory.Move(file, moveFileTo); } File.Delete(file); } MoveFilesToDirectory(dir, destDir, fileExt); } } catch ( IOException ex ) { Console.WriteLine(ex.Message); } } </code></pre>

2101

<p>In a controller (PHP, CodeIgniter) I'm adding scripts &amp; css to variables to be used in the view output. My initial coding looked like this:</p> <pre><code>private function _add_script($path, $where = self::ADD_LAST) { $html = "&lt;script src='$path'&gt;&lt;/script&gt;\n"; switch($where) { case self::ADD_LAST: array_push($this-&gt;_data['script'], $html); break; case self::ADD_FIRST: array_unshift($this-&gt;_data['script'], $html); break; } } private function _add_css($path, self::ADD_LAST) { $html = " &lt;link rel='stylesheet' href='$path'&gt;\n"; switch($where) { case self::ADD_LAST: array_push($this-&gt;_data['css'], $html); break; case self::ADD_FIRST: array_unshift($this-&gt;_data['css'], $html); break; } } </code></pre> <p>Well, I noticed that these two are basically just repeating themselves, so I immediately rewrote them into this format:</p> <pre><code>private function _add_script($path, $where = self::ADD_LAST) { $html = "&lt;script src='$path'&gt;&lt;/script&gt;\n"; $this-&gt;_add_external('script', $html, $where); } private function _add_css($path, $where = self::ADD_LAST) { $html = "&lt;link rel='stylesheet' href='$path'&gt;\n"; $this-&gt;_add_external('css', $html, $where); } private function _add_external($type, $html, $where) { switch($where) { case self::ADD_LAST: array_push($this-&gt;_data[$type], $html); break; case self::ADD_FIRST: array_unshift($this-&gt;_data[$type], $html); break; } } </code></pre> <p>Does the second version seem like the way to go? Or perhaps a 3rd alternative. The requirements call for being able to add elements to the list either before or after all other elements already in the list.</p>

2112

<p>I'm currently using an Open Source FTP library in all my projects as I've never managed to code a decent <strong>FTP Helper Library</strong> based on the C# 4.0 API.</p> <p>What do you think about this approach? I'm not quite versed in TDD but ideally I'd like to make this class as testable as possible.</p> <pre><code>public void DownloadFile(string host, string file, string user, string pass, string path) { if (!String.IsNullOrWhiteSpace(host) &amp;&amp; !String.IsNullOrWhiteSpace(file)) { Uri addr = new Uri(host + file); using (WebClient client = new WebClient()) { if (!String.IsNullOrWhiteSpace(user) &amp;&amp; !String.IsNullOrWhiteSpace(pass)) { client.Credentials = new NetworkCredential(user, pass); } if (!String.IsNullOrWhiteSpace(path)) { client.DownloadFile(addr, path); } } } } </code></pre>

2114

<p>I am a newbie to Python and have started object-oriented programming recently. I have implemented a "Rock Paper Scissors" application in OOP. I would like for you to evaluate my code, and tell me where can I improve my code and how I can better organize the functionality.</p> <pre><code>import random class RockPaperScissors(object): def setUserOption(self,val): self.__option = val def getValueFromList(self,option): l = ['rock','scissors','paper'] return l[option] def __getRandomValue(self,max): val = random.randint(1,max) return self.getValueFromList(val-1) def __getResult(self,t): self.__d = {('rock','scissors'):'rock breaks scissors - User has won',('rock','paper'):'rock is captured by paper - User has won',('scissors','paper'):'Scissors cut paper - User has won', ('scissors','rock'):'rock breaks scissors - Computer won',('paper','rock'):'rock is captured by paper - Computer won',('paper','scissors'):'Scissors cut paper - Computer won'} return self.__d[t] def __computeResult(self,computerOption): if computerOption == self.__option: return 'The user and computer choose the same option' else: return self.__getResult((self.__option,computerOption)) def printResult(self): computerOption = self.__getRandomValue(3) print 'User choice: ',self.__option print 'Computer choice: ',computerOption print self.__computeResult(computerOption) if __name__ == "__main__": print 'Welcome to rock paper scissors' print '1. Rock, 2. Paper, 3. Scissor' val = int(raw_input('Enter your choice Number: ')) if val &gt;=1 and val &lt;= 3: obj = RockPaperScissors() obj.setUserOption(obj.getValueFromList(val-1)) obj.printResult() else: raise ValueError('You are supposed to enter the choice given in the menu') </code></pre>

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<p>This essentially reads a specially-structured file from the scanner and then parses random phrases and prints them:</p> <pre><code>{ &lt;start&gt; &lt;greeting&gt; &lt;object&gt; } { &lt;greeting&gt; hello bonjour aloha } { &lt;object&gt; world universe multiverse } </code></pre> <p>Possible random phrases could be: "hello world", "bonjour universe", etc...</p> <p>Does anyone have some ideas as to how I might decrease the runtime? I heard you could run your code in parallel using multiple threads but was both unsure exactly how to do this and whether it would help at all? The slightest increase in runtime would be beneficial (having a little competition to see who can do it the fastest).</p> <p>It is not considered cheating so long as I do the majority of the programming, so please just point me in the right direction and provide suggestions.</p> <pre><code>package comprehensive; import java.io.File; import java.io.FileNotFoundException; import java.util.ArrayList; import java.util.HashMap; import java.util.Random; import java.util.Scanner; /** * Generates random phrases by reading the specified grammar file * and outputting the number of phrases specified by the user. * @author Jun Tang and John Newsome * */ public class RandomPhraseGenerator { public static HashMap&lt;String,ArrayList&lt;String&gt;&gt; map; public static void main(String[] args) throws FileNotFoundException{ Scanner k = new Scanner(new File(args[0])); int numPhrases = Integer.parseInt(args[1]); addKeys(k); while(numPhrases &gt; 0){ parseStrings(); numPhrases--; } } /** * Assimilates all of the keys and their associated values into map (a public static hashmap). * @param scan The scanner that is reading from the specified file. */ public static void addKeys(Scanner scan){ map = new HashMap&lt;String, ArrayList&lt;String&gt;&gt;(); while(scan.hasNextLine()){ if(scan.nextLine().equals("{")){ String key = scan.nextLine(); map.put(key, new ArrayList&lt;String&gt;()); String next = scan.nextLine(); while(!next.equals("}")){ map.get(key).add(next); next = scan.nextLine(); } } } } /** * Parses random String phrases from map and prints them. * Must already have assimilated keys and values prior by using the addKeys() method. */ public static void parseStrings(){ Random random = new Random(); StringBuilder strBuf = new StringBuilder((map.get("&lt;start&gt;").get(0))); int firstInstance = strBuf.indexOf("&lt;", 0); int secondInstance = strBuf.indexOf("&gt;", firstInstance); while(firstInstance &gt;= 0 &amp;&amp; secondInstance &gt;= 0){ String nonTerminal = strBuf.substring(firstInstance, secondInstance+1); strBuf.replace(firstInstance, secondInstance+1, (map.get(nonTerminal).get(random.nextInt(map.get(nonTerminal).size())))); firstInstance = strBuf.indexOf("&lt;", firstInstance); secondInstance = strBuf.indexOf("&gt;", firstInstance); } System.out.println(strBuf); } } </code></pre>

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<p>From <a href="http://mitpress.mit.edu/sicp/full-text/book/book-Z-H-18.html" rel="nofollow">SICP</a>:</p> <blockquote> <p><strong>Exercise 2.82</strong></p> <p>Show how to generalize apply-generic to handle coercion in the general case of multiple arguments. One strategy is to attempt to coerce all the arguments to the type of the first argument, then to the type of the second argument, and so on. Give an example of a situation where this strategy (and likewise the two-argument version given above) is not sufficiently general. (Hint: Consider the case where there are some suitable mixed-type operations present in the table that will not be tried.)</p> </blockquote> <p>I wrote this part before:</p> <pre><code>(define fn-registry '()) (define (get op param-types) (define (rec entry . rest) (define (all-equal a b) (if (symbol? a) (eq? a b) (and (= (length a) (length b)) (let loop ((x a) (y b)) (or (null? x) (and (eq? (car x) (car y)) (loop (cdr x) (cdr y)))))))) (let ((op-entry (car entry)) (param-types-entry (cadr entry)) (function-entry (caddr entry))) (if (and (eq? op-entry op) (all-equal param-types-entry param-types)) function-entry (if (null? rest) false (apply rec rest))))) (apply rec fn-registry)) (define (put op param-types fn) (set! fn-registry (cons (list op param-types fn) fn-registry))) </code></pre> <p>I wrote this coercion-registry code for this exercise:</p> <pre><code>(define coercion-registry '()) (define (put-coercion t1 t2 fn) (set! coercion-registry (cons (list t1 t2 fn) coercion-registry))) (define (get-coercion t1 t2) (define (rec entry . reg) (define t1-entry car) (define t2-entry cadr) (define fn-entry caddr) (cond ((and (eq? t1 (t1-entry entry)) (eq? t2 (t2-entry entry))) (fn-entry entry)) ((null? reg) false) (else (apply rec reg)))) (apply rec coercion-registry)) </code></pre> <p>This function takes any set of arguments and coerces them to be the same type:</p> <pre><code>(define (make-set . args) (define (rec tested current remains) (define (coerce-all to-type result items) (if (null? items) result (let ((t1-&gt;t2 (get-coercion (type-tag (car items)) to-type))) (cond ((eq? (type-tag (car items)) to-type) (coerce-all to-type (cons (car items) result) (cdr items))) ((not t1-&gt;t2) false) (else (coerce-all to-type (append result (list (t1-&gt;t2 (car items)))) (cdr items))))))) (let ((coerced-all (coerce-all (type-tag current) '() (append tested (cons current remains))))) (cond (coerced-all coerced-all) ((null? remains) false) (else (rec (append tested (list current)) (car remains) (cdr remains)))))) (rec '() (car args) (cdr args))) </code></pre> <p>I made some changes to apply-generic as well:</p> <pre><code>(define (apply-generic op . args) (let ((type-tags (map type-tag args))) (let ((proc (get op type-tags))) (if proc (apply proc (map contents args)) (let ((coerced-args (apply make-set args))) (if coerced-args (apply apply-generic (cons op coerced-args)) (error "No method found for these types" (list op type-tags)))))))) </code></pre> <p>This came from a previous activity:</p> <pre><code>(define (square x) (* x x)) (define (attach-tag type-tag contents) (if (or (symbol? contents) (number? contents)) contents (cons type-tag contents))) (define (type-tag datum) (cond ((pair? datum) (car datum)) ((number? datum) 'scheme-number) ((symbol? datum) 'scheme-symbol) (else (error "Bad tagged datum -- TYPE-TAG" datum)))) (define (contents datum) (cond ((pair? datum) (cdr datum)) ((or (number? datum) (symbol? datum)) datum) (else (error "Bad tagged datum -- CONTENTS" datum)))) (define (add x y) (apply-generic 'add x y)) (define (sub x y) (apply-generic 'sub x y)) (define (mul x y) (apply-generic 'mul x y)) (define (div x y) (apply-generic 'div x y)) (define (equ? x y) (apply-generic 'equ? x y)) (define (=zero? x) (apply-generic '=zero? x)) (define (install-scheme-number-package) (define (tag x) (attach-tag 'scheme-number x)) (put 'add '(scheme-number scheme-number) (lambda (x y) (tag (+ x y)))) (put 'sub '(scheme-number scheme-number) (lambda (x y) (tag (- x y)))) (put 'mul '(scheme-number scheme-number) (lambda (x y) (tag (* x y)))) (put 'div '(scheme-number scheme-number) (lambda (x y) (tag (/ x y)))) (put 'make 'scheme-number (lambda (x) (tag x))) (put 'equ? '(scheme-number scheme-number) =) (put '=zero? '(scheme-number) zero?) 'done) (define (make-scheme-number n) ((get 'make 'scheme-number) n)) (define (install-rational-package) ;; internal procedures (define (numer x) (car x)) (define (denom x) (cdr x)) (define (make-rat n d) (let ((g (gcd n d))) (cons (/ n g) (/ d g)))) (define (add-rat x y) (make-rat (+ (* (numer x) (denom y)) (* (numer y) (denom x))) (* (denom x) (denom y)))) </code></pre> <p>I added just this one function as part of what I needed in order to test apply-generic: </p> <pre><code>(put 'add-em '(rational rational rational rational) (lambda (a b c d) (add-rat a (add-rat b (add-rat c d))))) </code></pre> <p>More code from a previous activity:</p> <pre><code> (define (sub-rat x y) (make-rat (- (* (numer x) (denom y)) (* (numer y) (denom x))) (* (denom x) (denom y)))) (define (mul-rat x y) (make-rat (* (numer x) (numer y)) (* (denom x) (denom y)))) (define (div-rat x y) (make-rat (* (numer x) (denom y)) (* (denom x) (numer y)))) (define (equ?-rat x y) (and (= (numer x) (numer y)) (= (denom x) (denom y)))) (define (=zero?-rat x) (zero? (numer x))) ;; interface to rest of the system (define (tag x) (attach-tag 'rational x)) (put 'add '(rational rational) (lambda (x y) (tag (add-rat x y)))) (put 'sub '(rational rational) (lambda (x y) (tag (sub-rat x y)))) (put 'mul '(rational rational) (lambda (x y) (tag (mul-rat x y)))) (put 'div '(rational rational) (lambda (x y) (tag (div-rat x y)))) (put 'equ? '(rational rational) equ?-rat) (put '=zero? '(rational) =zero?-rat) (put 'make 'rational (lambda (n d) (tag (make-rat n d)))) 'done) (define (make-rational n d) ((get 'make 'rational) n d)) (define (real-part z) (apply-generic 'real-part z)) (define (imag-part z) (apply-generic 'imag-part z)) (define (magnitude z) (apply-generic 'magnitude z)) (define (angle z) (apply-generic 'angle z)) (define (install-complex-package) ;; imported procedures from rectangular and polar packages (define (make-from-real-imag x y) ((get 'make-from-real-imag 'rectangular) x y)) (define (make-from-mag-ang r a) ((get 'make-from-mag-ang 'polar) r a)) ;; internal procedures (define (add-complex z1 z2) (make-from-real-imag (+ (real-part z1) (real-part z2)) (+ (imag-part z1) (imag-part z2)))) (define (sub-complex z1 z2) (make-from-real-imag (- (real-part z1) (real-part z2)) (- (imag-part z1) (imag-part z2)))) (define (mul-complex z1 z2) (make-from-mag-ang (* (magnitude z1) (magnitude z2)) (+ (angle z1) (angle z2)))) (define (div-complex z1 z2) (make-from-mag-ang (/ (magnitude z1) (magnitude z2)) (- (angle z1) (angle z2)))) (define (equ?-complex z1 z2) (and (= (real-part z1) (real-part z2)) (= (imag-part z1) (imag-part z2)))) (define (=zero?-complex z) (and (zero? (real-part z)) (zero? (imag-part z)))) ;; interface to rest of the system (define (tag z) (attach-tag 'complex z)) (put 'add '(complex complex) (lambda (z1 z2) (tag (add-complex z1 z2)))) (put 'sub '(complex complex) (lambda (z1 z2) (tag (sub-complex z1 z2)))) (put 'mul '(complex complex) (lambda (z1 z2) (tag (mul-complex z1 z2)))) (put 'div '(complex complex) (lambda (z1 z2) (tag (div-complex z1 z2)))) (put 'make-from-real-imag 'complex (lambda (x y) (tag (make-from-real-imag x y)))) (put 'make-from-mag-ang 'complex (lambda (r a) (tag (make-from-mag-ang r a)))) (put 'equ? '(complex complex) equ?-complex) (put '=zero? '(complex) =zero?-complex) 'done) (define (install-polar-package) ;; internal procedures (define (magnitude z) (car z)) (define (angle z) (cdr z)) (define (make-from-mag-ang r a) (cons r a)) (define (real-part z) (* (magnitude z) (cos (angle z)))) (define (imag-part z) (* (magnitude z) (sin (angle z)))) (define (make-from-real-imag x y) (cons (sqrt (+ (square x) (square y))) (atan y x))) (define (equ? x y) (and (= (magnitude x) (magnitude y)) (= (angle x) (angle y)))) (define (=zero? x) (zero? (magnitude x))) ;; interface to the rest of the system (define (tag x) (attach-tag 'polar x)) (put 'real-part '(polar) real-part) (put 'imag-part '(polar) imag-part) (put 'magnitude '(polar) magnitude) (put 'angle '(polar) angle) (put 'equ? '(polar polar) equ?) (put '=zero? '(polar) =zero?) (put 'make-from-real-imag 'polar (lambda (x y) (tag (make-from-real-imag x y)))) (put 'make-from-mag-ang 'polar (lambda (r a) (tag (make-from-mag-ang r a)))) 'done) (define (install-rectangular-package) ;; internal procedures (define (real-part z) (car z)) (define (imag-part z) (cdr z)) (define (make-from-real-imag x y) (cons x y)) (define (magnitude z) (sqrt (+ (square (real-part z)) (square (imag-part z))))) (define (angle z) (atan (imag-part z) (real-part z))) (define (make-from-mag-ang r a) (cons (* r (cos a)) (* r (sin a)))) (define (equ? x y) (and (= (real-part x) (real-part y)) (= (imag-part x) (imag-part y)))) (define (=zero? x) (and (zero? (real-part x)) (zero? (imag-part x)))) ;; interface to the rest of the system (define (tag x) (attach-tag 'rectangular x)) (put 'real-part '(rectangular) real-part) (put 'imag-part '(rectangular) imag-part) (put 'magnitude '(rectangular) magnitude) (put 'angle '(rectangular) angle) (put 'equ? '(rectangular rectangular) equ?) (put '=zero? '(rectangular) =zero?) (put 'make-from-real-imag 'rectangular (lambda (x y) (tag (make-from-real-imag x y)))) (put 'make-from-mag-ang 'rectangular (lambda (r a) (tag (make-from-mag-ang r a)))) 'done) (define (make-complex-from-real-imag x y) ((get 'make-from-real-imag 'complex) x y)) (define (make-complex-from-mag-ang r a) ((get 'make-from-mag-ang 'complex) r a)) (install-rational-package) (install-scheme-number-package) (install-complex-package) (install-polar-package) (install-rectangular-package) </code></pre> <p>Register the coercion:</p> <pre><code>(put-coercion 'scheme-number 'rational (lambda (a) (make-rational a 1))) </code></pre> <p>And finally, the test:</p> <pre><code>(apply-generic 'add-em (make-rational 3 4) 2 3 4) </code></pre> <p>There is more code in here than would be necessary to test only the new functionality. I found it easier to test the new apply-generic by including the code from previous examples. I'm sorry that it may make it a bit harder to follow exactly what I'm asking here, but please do your best to give me feedback.</p> <p>How can I improve this code?</p>

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<p>I've been rolling around several ideas or approaches in my head, and none seem any more useful or "right" than another. I'm sure this is extremely objective but I'm looking for a close-to-definitive answer on the object oriented approach to large block string storage and output in PHP. Given the following example, how could I change my approach in a way that might cause Zeev Suraski to pat me on the back and say Mazel Tov (beside using HTML5)?</p> <pre><code>&lt;?php class OutputConstructor extends ContentRetriever // Or whatever I decide to name it { protected $htmlHeadBlock; public function __construct() { $this-&gt;setHtmlHeadBlock(); } protected function setHtmlHeadBlock() { ob_start(); ?&gt; &lt;!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"&gt; &lt;html xmlns="http://www.w3.org/1999/xhtml"&gt; &lt;head&gt; &lt;meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /&gt; &lt;title&gt;&lt;?php echo $this-&gt;pageTitle; ?&gt;&lt;/title&gt; &lt;link rel="shortcut icon" href="images/favicon.ico" type="image/x-icon" /&gt; &lt;link rel="icon" href="images/favicon.ico" type="image/x-icon" /&gt; &lt;meta name="description" content="&lt;?php echo $this-&gt;pageDescription; ?&gt;" /&gt; &lt;meta name="keywords" content="&lt;?php echo $this-&gt;pageKeywords; ?&gt;" /&gt; &lt;link type="text/css" rel="stylesheet" href="css/style.css" /&gt; &lt;script type="text/javascript" src="js/functions.js"&gt;&lt;/script&gt; &lt;/head&gt; &lt;?php $this-&gt;htmlHeadBlock = ob_get_clean(); } public function getHtmlHeadBlock() { return $this-&gt;htmlHeadBlock; } } // End of OutputConstructor ?&gt; </code></pre> <p>The general theme I'm going with in this example class is that on construction, html is stored in a variable via output buffer and then returned by a public method. When evaluating this code, consider that the html will not be static. Page title, description, keywords and the such will be subbed out with dynamic property references. My overall question is: In object oriented programming, ideally where should the output be stored? PHP's <code>DOMDocument</code> class, however useful, doesn't really answer this question for me. Also in this instance, is there any best practice trade-off between using an output buffer and heredoc syntax? Thanks in advance for your guidance!</p>

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<p>I have the following construction in the program:</p> <pre><code> while(true) { &lt;...&gt; try { JobManager.markJobCompleted(unitOfWork.getSqlFactory(), jobId, dataOut); } catch (DbLogicException e) { logger.error(JobManager.CANNOT_MARK_JOB_COMPLETED + jobId, e); try { unitOfWork.rollback(); } catch (DbLogicException e1) { logger.error(UnitOfWork.CANNOT_ROLLBACK_TRANSACTION, e1); unitOfWork.closeSilently(); return; } continue; } &lt;...&gt; } </code></pre> <p>So, the logic is the following:</p> <ol> <li>Trying to mark the job completed</li> <li>If we fail, try to rollback transaction and proceed to next job item</li> <li>If transaction rollback failed, something is seriously wrong here, aborting everything</li> </ol> <p>This construction looks a little clumsy to me. Is there a way to refactor it so it would become... beautiful?</p>

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<p>I finished the Ruby chapter in <a href="http://pragprog.com/titles/btlang/seven-languages-in-seven-weeks" rel="nofollow"><em>Seven Languages in Seven Weeks</em></a>. It tries to make you familiar with the core concepts of several languages rather quickly. Dutifully I did all exercises, but most likely they can be improved to be more Ruby-like. I'll post my code samples one by one, so I can apply things learned in previous questions to later questions.</p> <p>Day 1</p> <blockquote> <p>Write a program that picks a random number. Let a player guess the number, telling the player whether the guess is too low or too high.</p> </blockquote> <pre><code>range = (0..10) to_guess = range.min + rand(range.max - range.min) guessed = false while !guessed puts "Guess a number, between #{range.min} and #{range.max}" guess = gets int = guess.to_i if int == to_guess puts 'Correct!' guessed = true else puts int &gt; to_guess ? 'Lower' : 'Higher' end end </code></pre> <hr> <p>After sepp2k's comments:</p> <pre><code>class Range def size self.end - self.begin end end range = 0..10 to_guess = range.begin + rand(range.size) guessed = false until guessed puts "Guess a number, between #{range.begin} and #{range.end}" guess = gets int = guess.to_i if int == to_guess puts 'Correct!' guessed = true else puts int &gt; to_guess ? 'Lower' : 'Higher' end end </code></pre>

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<p>As an exercise, I've implemented a simple reader macro in Common Lisp (using SBCL). It converts Octal (unsigned integers only) into numbers.</p> <p>Usage:</p> <pre><code>* #z1234 668 </code></pre> <p>The code:</p> <pre><code>(defun oct-string-to-number (string) "Converts an octal string to a number. Only digits from 0 - 7 are accepted; sign or decimal point symbols will cause oct-to-number to fail" (setq place 1) (setq result 0) (setq digits '(#\0 #\1 #\2 #\3 #\4 #\5 #\6 #\7)) (loop for char across (reverse string) do (setq pos (position char digits)) (setq result (+ result (* pos place))) (setq place (* 8 place))) result) (defun slurp-octal-digits (stream) (setq string (make-array 0 :element-type 'character :fill-pointer 0 :adjustable t)) "Slurps all digits from 0 - 7 from a stream into a string, stopping at EOF, no data, or a non-digit character." (setq digits '(#\0 #\1 #\2 #\3 #\4 #\5 #\6 #\7)) (with-output-to-string (out) (loop do (setq char (read-char stream)) (setq isnum nil) (if char (progn (setq isnum (find char digits)) (if isnum (vector-push-extend char string) (unread-char char stream)))) while (not (eq nil isnum)))) string) (defun octal-string-transformer (stream subchar args) "Slurps an octal number from stream, and converts it to a number. Number must be an unsigned integer." (setq oct-string (slurp-octal-digits stream)) (oct-string-to-number oct-string)) ;; Sets #z to call octal-string-transformer, so e.g. #z1234 will evaluate to 668. Use #z as SBCL has #o already :-) (set-dispatch-macro-character #\# #\z #'octal-string-transformer) </code></pre> <p>I'm quite new to Common Lisp, so I'd greatly appreciate feedback on everything: formatting, style, idiom, correctness :-)</p> <p><em>Edited to add:</em> Actually, the formatting in the pasted code snippet is rendered oddly; indentation that is present when I edit vanishes when I submit. So maybe be a bit gentle with feedback about the formatting ;-)</p>

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<p>In <a href="https://stackoverflow.com/questions/5801586/idiomatic-haskell-for-database-abstraction">this</a> post I asked about what would be idiomatic haskell database abstraction. I had been thinking for it a while, and the first answer was similar to what I had in mind, and I wrote a proof-of-concept of it. Discarding the abomination that is the schema, what would you change, and why?</p> <p>Database.hs</p> <pre><code>{-# LANGUAGE GeneralizedNewtypeDeriving #-} module Database ( runDB , quickQuery , prepare , execute , fetchRowAl , DB (..) , module Database.HDBC.SqlValue ) where import qualified Database.HDBC as H import Database.HDBC.SqlValue import Database.HDBC.Sqlite3 import Control.Monad.Reader newtype DB a = D (ReaderT Connection IO a) deriving (Monad, MonadReader Connection, MonadIO) runDB :: FilePath -&gt; DB b -&gt; IO b runDB path (D x) = do c &lt;- connectSqlite3 path mkSchema c r &lt;- runReaderT x c H.disconnect c return r mkSchema conn = do tables &lt;- H.getTables conn unless ("Location" `elem` tables) $ do H.handleSqlError $ H.quickQuery' conn "CREATE TABLE Location (location TEXT PRIMARY KEY)" [] return () unless ("Person" `elem` tables) $ do H.handleSqlError $ H.quickQuery' conn (unwords [ "CREATE TABLE Person" , "(id INTEGER PRIMARY KEY AUTOINCREMENT," , "name TEXT NOT NULL," , "age INT NOT NULL," , "location TEXT," , "FOREIGN KEY (location) REFERENCES Location (location))"]) [] return () quickQuery :: String -&gt; [SqlValue] -&gt; DB [[SqlValue]] quickQuery q v = ask &gt;&gt;= \c -&gt; liftIO $ H.quickQuery c q v prepare :: String -&gt; DB H.Statement prepare q = ask &gt;&gt;= \c -&gt; liftIO $ H.prepare c q execute :: H.Statement -&gt; [SqlValue] -&gt; DB Integer execute stmt v = liftIO $ H.execute stmt v fetchRowAl :: H.Statement -&gt; DB (Maybe [(String, SqlValue)]) fetchRowAl = liftIO . H.fetchRowAL </code></pre> <p>Model.hs</p> <pre><code>module Model where import Database data Person = Person (Maybe Int) String Int Location newtype Location = Location String deriving (Eq) instance Eq Person where (Person _ a b c) == (Person _ a' b' c') = a == a' &amp;&amp; b == b' &amp;&amp; c == c' saveLocation :: Location -&gt; DB () saveLocation (Location x) = quickQuery "INSERT OR IGNORE INTO Location VALUES (?)" [toSql x] &gt;&gt; return () retrieveLocation :: String -&gt; DB (Maybe Location) retrieveLocation x = do r &lt;- quickQuery "SELECT location FROM Location WHERE location=?" [toSql x] case r of [] -&gt; return Nothing [[y]] -&gt; return $ Just $ Location $ fromSql y savePerson :: Person -&gt; DB () savePerson (Person _ n a l@(Location loc)) = do saveLocation l quickQuery "INSERT INTO Person (name, age, location) VALUES (?, ?, ?)" [toSql n, toSql a, toSql loc] return () retrievePersons name = do r &lt;- quickQuery "SELECT id, name, age, location FROM Person WHERE name=?" [toSql name] let persons = map makePerson r return persons where makePerson [sid, sname, sage, slocation] = Person (fromSql sid) (fromSql sname) (fromSql sage) (Location (fromSql slocation)) </code></pre> <p>tests.hs</p> <pre><code>import Test.HUnit import Test.Framework.Providers.HUnit import Test.Framework (defaultMain, testGroup) import System.Directory import Database.HDBC (quickQuery') import Control.Monad.Reader import Control.Applicative import Data.Maybe import Database import Model runTest f = runDB "/tmp/test.db" f &lt;* removeFile "/tmp/test.db" testConnected = runTest $ do c &lt;- ask r &lt;- liftIO $ quickQuery' c "SELECT 'foo' AS value" [] liftIO $ assertBool "Return value should not be empty" (length r &gt; 0) testQuickQuery = runTest $ do [[x]] &lt;- quickQuery "SELECT ? AS value" [toSql "foo"] liftIO $ assertBool "quickQuery" (fromSql x == "foo") testPrepared = runTest $ do stmt &lt;- prepare "SELECT ? AS value" execute stmt [toSql "foo"] (Just r) &lt;- fetchRowAl stmt let (Just x) = lookup "value" r liftIO $ assertBool "prepared" (fromSql x == "foo") testRetrieveLocationNothing = runTest $ do r &lt;- retrieveLocation "Turku" liftIO $ assertBool "Location nothing" (isNothing r) testSaveLocation = runTest $ do let turku = Location "Turku" saveLocation turku (Just loc) &lt;- retrieveLocation "Turku" liftIO $ assertBool "loc == turku" (loc == turku) testSavePerson = runTest $ do let person = Person Nothing "Person" 25 $ Location "Turku" savePerson person [per] &lt;- retrievePersons "Person" liftIO $ assertBool "model == db" $ validate person per where validate _ (Person Nothing _ _ _) = False validate a b = a == b tests = [ testGroup "Database" [ testCase "connected" testConnected , testCase "quickQuery" testQuickQuery , testCase "testPrepared" testPrepared ] , testGroup "Model" [ testCase "saveLocation" testSaveLocation , testCase "savePerson" testSavePerson , testCase "testRetrieveLocationNothing" testRetrieveLocationNothing ] ] main = defaultMain tests </code></pre>

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<p>I finished the Ruby chapter in <a href="http://pragprog.com/titles/btlang/seven-languages-in-seven-weeks" rel="nofollow noreferrer">Seven Languages in Seven Weeks</a>. It tries to make you familiar with the core concepts of several languages rather quickly. Dutifully I did all exercises, but most likely they can be improved to be more Ruby-like.</p> <blockquote> <p>Write a simple grep that will print the lines of a file having any occurrences of a phrase anywhere in that line (in my example 'bleh'). Include line numbers.</p> </blockquote> <pre><code>File.open( 'grepFile.txt', 'r' ) do |file| lines = [] line_number = 1 file.readlines.each do |line| lines[line_number] = line line_number += 1 end lines.each_index do |i| line = lines[i] puts "line #{i.to_s}: #{line}" if line =~ /bleh/ end end </code></pre>

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<p>I finished the Ruby chapter in <a href="http://pragprog.com/titles/btlang/seven-languages-in-seven-weeks" rel="nofollow noreferrer">Seven Languages in Seven Weeks</a>. It tries to make you familiar with the core concepts of several languages rather quickly. Dutifully I did all exercises, but most likely they can be improved to be more Ruby-like.</p> <blockquote> <p>Given: a CSV file structured with a first line with headers and subsequent rows with data.</p> <pre><code>one, two lions, tigers </code></pre> <p>Create a module which loads the header and values from a CSV file, based on the name of the implementing class. (RubyCSV -> "rubycsv.txt") Support an <code>each</code> method which returns a <code>CsvRow</code> object. Use <code>method_missing</code> to return the value for the column for a given heading. E.g. usage which will print "lions":</p> <pre><code>m = RubyCsv.new m.each { |row| p row.one } </code></pre> </blockquote> <p>My implementation:</p> <pre><code>class CsvRow attr :row_hash def initialize( row_hash ) @row_hash = row_hash end def method_missing( name, *args ) @row_hash[ name.to_s ] end end module ActsAsCsv attr_accessor :headers, :csv_contents def self.included( base ) base.extend ClassMethods end module ClassMethods def acts_as_csv include InstanceMethods end end module InstanceMethods def read @csv_contents = [] filename = self.class.to_s.downcase + '.txt' file = File.new( filename ) @headers = file.gets.chomp.split( ', ' ) file.each do |row| @csv_contents &lt;&lt; row.chomp.split( ', ' ) end end def initialize read end def each @csv_contents.each do |content| hash = {} @headers.zip( content ).each { |i| hash[ i[0] ] = i[1] } yield CsvRow.new hash end end end end class RubyCsv # No inheritance! You can mix it in. include ActsAsCsv acts_as_csv end </code></pre>

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<p>I have been working with C# for quite some time but relatively new to the concepts of lambdas and Linq. I was working with a Linq To SQL example and trying to write a generic solution for executing a search against a collection of entities (eg. list of <code>Customer</code> objects) where the search parameter will be specified by passing a partially filled object of the entity class itself. I was doing this just to ensure that a person does not have to go on specifying different overloads for different searches based on the entity class attributes and trying to write a generic solution which will cater to any entity class. </p> <p>Hence I used reflection and an array of predicates to successively apply the Where clauses to the collection.</p> <h2>Client App</h2> <pre><code>using (CustomerManager oCustomerManager = new CustomerManager()) { IEnumerable&lt;Customer&gt; customers = oCustomerManager.Load(); Customer oSearchCustomer = new Customer(); oSearchCustomer.City = "London"; oSearchCustomer.ContactName = "Thomas Hardy"; IEnumerable&lt;Customer&gt; customerList = oCustomerManager.Search(oSearchCustomer); foreach (Customer customer in customerList) { Console.WriteLine(customer.ToString()); } } </code></pre> <h2>Manager Class</h2> <pre><code>public IEnumerable&lt;Customer&gt; Search(Customer searchObject) { IEnumerable&lt;Customer&gt; customers = DataContext.Customers; List&lt;Func&lt;Customer, bool&gt;&gt; result = DataContext.Customers.GenerateFilterClause&lt;Customer&gt;(searchObject); foreach (var item in result) { customers = customers.Where(item); } return customers; } </code></pre> <h2>Extension Method Utility Class</h2> <pre><code>public static class UtilityExtensions { public static List&lt;Func&lt;T, bool&gt;&gt; GenerateFilterClause&lt;T&gt;(this IEnumerable&lt;T&gt; collection, T searchEntity) { List&lt;Func&lt;T, bool&gt;&gt; whereFilterList = new List&lt;Func&lt;T, bool&gt;&gt;(); Func&lt;T, bool&gt; predicate = null; var propertyList = searchEntity.GetType().GetProperties(); foreach (PropertyInfo p in propertyList) { if (p.GetCustomAttributes(false).OfType&lt;ColumnAttribute&gt;().Count() &gt; 0) { string propName = p.Name; var searchVal = searchEntity.GetType().GetProperty(propName).GetValue(searchEntity,null); if (searchVal != null) { predicate = new Func&lt;T, bool&gt;(entity =&gt; propertyWhereClause(entity, searchEntity, propName, searchVal)); whereFilterList.Add(predicate); } } } return whereFilterList; } private static bool propertyWhereClause&lt;T&gt;(T obj, T searchEntity, string propertyName, object searchVal) { return obj.GetType().GetProperty(propertyName).GetValue(obj, null).Equals(searchVal); } } </code></pre> <p>While the solution is working, I have two specific questions:</p> <ul> <li>What are the drawbacks of this solution? I was hoping to have inputs regarding performance and cleaner way to rewrite the code.</li> <li>Can anyone suggest a more efficient and better solution? That would help me to understand the proper way to utilize the power of lambdas and Linq.</li> </ul>

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<p>Both functions look fairly similar to each other, but they are different in the type of string. I have 6 functions like this and all differ only in the "string cmd". Any ideas on how I can put it all into one?</p> <pre><code>public void getFrmSingProgTbl(int flg) { if (flg == 1) { object[] astatus = new object[1]; astatus = td.CheckOk(td.t1snd); string status = (string)astatus[0]; if (status == "true") { string cmd = getCurrTime() + "|" + "part-type" + "|" + t1prtNameTxt.Text + "\n"; cmd += getCurrTime() + "|" + "operation-type" + "|" + t1oprNameTxt.Text + "\n"; string showCmd = "Part Type - " + t1prtNameTxt.Text + "\nOperation - " + t1oprNameTxt.Text; if (MessageBox.Show(showCmd, "Confirm", MessageBoxButtons.YesNo) == DialogResult.Yes) { HandleAfterSend(td.t1snd, td.t1stp, flg, td.t1btn); sndData(cmd,1); } } else { this.ActiveControl = (TextBox)astatus[1]; MessageBox.Show(status, "Error"); } } else if (flg == 2) { object[] astatus = new object[1]; astatus = td.CheckOk(td.t1stp); string status = (string)astatus[0]; if (status == "true") { string cmd = getCurrTime() + "|" + "part-count-good" + "|" + t1gpTxt.Text + "\n"; cmd += getCurrTime() + "|" + "part-count-bad" + "|" + t1bpTxt.Text + "\n"; string showCmd = "Good Parts - " + t1gpTxt.Text + "\nBad Parts - " + t1bpTxt.Text; if (td.CheckNumeric(td.t1stp)) { if (MessageBox.Show(showCmd, "Confirm", MessageBoxButtons.YesNo) == DialogResult.Yes) { HandleAfterSend(td.t1stp, td.t1snd, flg, td.t1btn); sndData(cmd,0); } } else { MessageBox.Show("Enter only numbers for Part Count","Error"); } } else { this.ActiveControl = (TextBox)astatus[1]; MessageBox.Show(status, "Error"); } } } public void getFrmSingFixtTbl(int flg) { if (flg == 1) { object[] astatus = new object[1]; astatus = td.CheckOk(td.t3snd); string status = (string)astatus[0]; if (status == "true") { string cmd = getCurrTime() + "|" + "part-type" + "|" + t3prtNameTxt.Text + "\n"; cmd += getCurrTime() + "|" + "operation-type" + "|" + t3oprNameTxt.Text + "\n"; cmd += getCurrTime() + "|" + "fixture-positions" + "|" + t3fixPosnTxt.Text + "\n"; string showCmd = "Part Type" + " - " + t3prtNameTxt.Text + "\n"; showCmd += "Operation" + " - " + t3oprNameTxt.Text + "\n"; showCmd += "Parts per Fixture " + " - " + t3fixPosnTxt.Text + "\n"; if (MessageBox.Show(showCmd, "Confirm", MessageBoxButtons.YesNo) == DialogResult.Yes) { HandleAfterSend(td.t3snd, td.t3stp, flg, td.t3btn); sndData(cmd,1); } } else { this.ActiveControl = (TextBox)astatus[1]; MessageBox.Show(status, "Error"); } } else if (flg == 2) { object[] astatus = new object[1]; astatus = td.CheckOk(td.t3stp); string status = (string)astatus[0]; if (status == "true") { string cmd = getCurrTime() + "|" + "part-count-good" + "|" + t3gpTxt.Text + "\n"; cmd += getCurrTime() + "|" + "part-count-bad" + "|" + t3bpTxt.Text + "\n"; string showCmd = "Good Parts" + " - " + t3gpTxt.Text + "\n"; showCmd += "Bad Parts" + " - " + t3bpTxt.Text + "\n"; if (td.CheckNumeric(td.t3stp)) { if (MessageBox.Show(showCmd, "Confirm", MessageBoxButtons.YesNo) == DialogResult.Yes) { HandleAfterSend(td.t3stp, td.t3snd, flg, td.t3btn); sndData(cmd,0); } } else { MessageBox.Show("Enter only numbers for Part Count","Error"); } } else { this.ActiveControl = (TextBox)astatus[1]; MessageBox.Show(status, "Error"); } } } </code></pre>

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<p>I have small Class which handles user's information. (name, surname, login, hash of password). Also this class can activate, register and login the user. This means I should connect to DB. Is it normal? I'm using Pear MDB2 to connect to DB. </p> <p>Does it mean that every instance of User will have MDB2 object initialised?</p> <pre><code>class User { private $login; private $hash; private $name; /* some getters and setters */ // // public function get_name() { return $this-&gt;name } // .. // private $connect; // MDB2 connection private $dsn = ""; // connection config public function exists() { // return true if User exists require ('MDB2.php'); $this-&gt;connect = MDB2::connect($this-&gt;dsn); // check } } </code></pre> <p>Should I make $connect and $dsn variables static? Or may be I should use some pattern for this idea?</p> <p>Update: (kind of decision)</p> <p>I store database connection in static variable:</p> <pre><code>class DataBase { // connections options static public $connect = NULL; // MDB2 connection variable static public $dsn = "pgsql://user:pass@IP/database"; static public $connected = false; static function reportError() { if (PEAR::isError(self::$connect)) { $res["success"]=false; $res["errors"][] = self::$connect-&gt;getMessage(); echo json_encode($res); exit; } } //: reportError } //: Class DataBase </code></pre> <p>So If I want to connect to DB I write:</p> <pre><code>// connect only if it's not connected if (!DataBase::$connected) { require_once('MDB2.php'); // Pear MDB2 class DataBase::$connect = MDB2::factory(DataBase::$dsn); // connection DataBase::$connected = true; // Flag that we're already connected } </code></pre> <p>It's normal? Or I should make it another way?</p>

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<p>I'm giving a lecture on basic programming to first-year mathematics students. The programming language is Java (defined by curriculum).</p> <p>Last week I gave the following task:</p> <blockquote> <p>Write a program, that reads in the date of birth of the user separated into year, month and day and subsequently calculates the days the user has lived until today.<br> Do consider leap years.</p> </blockquote> <p>This task seems not to be too hard, but there are some restrictions (as they are first-year students and never had had any experiences in programming):</p> <ol> <li>only the basic data types are known (<code>int</code>, <code>double</code>, <code>boolean</code>, <code>String</code> etc.)</li> <li>arrays are <em>not</em> known</li> <li>writing own functions is <em>not</em> known (i.e. everything is within the <code>main</code>)</li> <li>except of <code>System.out.print</code>/<code>ln</code> none of the Java API functions are known</li> <li>user input is realised through a provided method <code>readInteger(String promt)</code> (the students just use it, but don't know why and how it works)</li> </ol> <p>Here I present my sample solution and would like to know, whether there are some more possibilities of "smoothing" the code, optimising it or just increasing the readability. Only tweaks and tricks are allowed, which can be done given the knowledge-restrictions above.</p> <pre><code>public static void main(String[] args) { // define today's day final int TODAY_YEAR = 2011, TODAY_MONTH = 4, TODAY_DAY = 29; // define a leapyear in the past final int LEAPYEAR = 1904; // is the current year a leapyear? boolean todayIsLeapyear = false; // get user input int birthYear = readInteger("Please enter the year of your birth:"); int birthMonth = readInteger("Please enter the month of your birth:"); int birthDay = readInteger("Please enter the day of your birth:"); // check input for validity boolean inputOK = true; int birthYearLeapShift = 0; boolean birthYearWasLeap = false; if (birthYear &gt; 2011 || birthMonth &gt; 12) { System.out.println("Your input was not correct."); if (birthYear &gt; 2011) { System.out.println("You are from the future! How is it there?"); } else { System.out.println("We will calculate in the usual gregorian calendar."); } inputOK = false; } else { // calculate shift of year of birth to the prior leapyear birthYearLeapShift = (birthYear - LEAPYEAR) % 4; birthYearWasLeap = (birthYearLeapShift == 0); // check the input of the month of birth for validity switch (birthMonth) { case 1: //january inputOK = (birthDay &lt;= 31); break; case 2: //february inputOK = (birthDay &lt;= 28); inputOK = (birthDay &lt;= 29 &amp;&amp; birthYearWasLeap); break; case 3: //march inputOK = (birthDay &lt;= 31); break; case 4: //april inputOK = (birthDay &lt;= 30); break; case 5: //may inputOK = (birthDay &lt;= 31); break; case 6: //june inputOK = (birthDay &lt;= 30); break; case 7: //july inputOK = (birthDay &lt;= 31); break; case 8: //august inputOK = (birthDay &lt;= 31); break; case 9: //september inputOK = (birthDay &lt;= 30); break; case 10: //october inputOK = (birthDay &lt;= 31); break; case 11: //november inputOK = (birthDay &lt;= 30); break; case 12: //december inputOK = (birthDay &lt;= 31); break; } } if (inputOK) { // calculate the days fo the current year int daysInCurrYear = TODAY_DAY; switch (TODAY_MONTH - 1) { case 11: daysInCurrYear += 30; case 10: daysInCurrYear += 31; case 9: daysInCurrYear += 30; case 8: daysInCurrYear += 31; case 7: daysInCurrYear += 31; case 6: daysInCurrYear += 30; case 5: daysInCurrYear += 31; case 4: daysInCurrYear += 30; case 3: daysInCurrYear += 31; case 2: daysInCurrYear += todayIsLeapyear ? 29 : 28; case 1: daysInCurrYear += 31; } // calculate the lived (full) days in the year of birth int daysInBirthYear = 0; switch (birthMonth) { case 1: daysInBirthYear += 31 - birthDay; case 2: if (birthYearWasLeap) { daysInBirthYear += (birthMonth == 2) ? (29 - birthDay) : 29; } else { daysInBirthYear += (birthMonth == 2) ? (28 - birthDay) : 28; } case 3: daysInBirthYear += (birthMonth == 3) ? (31 - birthDay) : 31; case 4: daysInBirthYear += (birthMonth == 4) ? (30 - birthDay) : 30; case 5: daysInBirthYear += (birthMonth == 5) ? (31 - birthDay) : 31; case 6: daysInBirthYear += (birthMonth == 6) ? (30 - birthDay) : 30; case 7: daysInBirthYear += (birthMonth == 7) ? (31 - birthDay) : 31; case 8: daysInBirthYear += (birthMonth == 8) ? (31 - birthDay) : 31; case 9: daysInBirthYear += (birthMonth == 9) ? (30 - birthDay) : 30; case 10: daysInBirthYear += (birthMonth == 10) ? (31 - birthDay) : 31; case 11: daysInBirthYear += (birthMonth == 11) ? (30 - birthDay) : 30; case 12: daysInBirthYear += (birthMonth == 12) ? (31 - birthDay) : 31; } // calculate the full lived years since birth int fullYearsSinceBirth = TODAY_YEAR - birthYear - 1; // ... and considere the leapyears lived int leapyearsLived = (fullYearsSinceBirth + birthYearLeapShift) / 4; // and calculate the lived days in the lived full years int daysInFullYears = fullYearsSinceBirth * 365 + leapyearsLived; // add everything together int daysLived = daysInBirthYear + daysInFullYears + daysInCurrYear; // and finally return the result System.out.println("You have been living for " + daysLived + " days now."); System.out.println("In addition, this is approximately " + (daysLived / 30) + " full months and " + fullYearsSinceBirth + " full years."); System.out.println("Congratulations!"); } } </code></pre>

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<blockquote> <p>I remember once going to see [Srinivasa Ramanujan] when he was ill at Putney. I had ridden in taxi cab number 1729 and remarked that the number seemed to me rather a dull one, and that I hoped it was not an unfavorable omen. "No," he replied, "it is a very interesting number; it is the smallest number expressible as the sum of two cubes in two different ways." [G. H. Hardy as told in <a href="http://en.wikipedia.org/wiki/1729_%28number%29" rel="nofollow noreferrer">"1729 (number)"</a>]</p> </blockquote> <p>In <a href="http://www.forbes.com/2009/02/06/math-archimedes-churchill-opinions-contributors_0207_joseph_tartakovsky.html" rel="nofollow noreferrer">"Math Wrath"</a> Joseph Tartakovsky says about this feat:</p> <blockquote> <p>So what? Give me two minutes and my calculator watch, and I'll do the same without exerting any little gray cells.</p> </blockquote> <p>I don't know how Mr. Tartakovsky would accomplish that proof on a calculator watch, but the following is my scheme function that enumerates numbers starting at 1 and stops when it finds a number that is expressable in two seperate ways by summing the cubes of two positive numbers. And it indeeds returns 1729.</p> <p>There are two areas where I would appreciate suggestions for improvement. One area is, being new to scheme, style and idiom. The other area is around the calculations. Sisc does not return exact numbers for roots, even when they could be.</p> <p>For example <code>(expt 27 1/3)</code> yields 2.9999999999999996. But I do get exact results when cubing an exact number, <code>(expt 3 3)</code> yields <code>27</code>. My solution was to get the exact floor of a cube root and then test against the cube of the floor and the cube of the floor plus one, counting as a match if either match. This solution seems messy and hard to reason about. Is there a more straightforward way?</p> <pre><code>; Find the Hardy-Ramanujan number, which is the smallest positive ; integer that is the sum of the cubes of two positivie integers in ; two seperate ways. (define (hardy-ramanujan-number) (let ((how-many-sum-of-2-positive-cubes ; while i^3 + 1 &lt; n/1 ; tmp := exact_floor(cube-root(n - i^3)) ; if n = i^3 + tmp^3 or n = i^3 + (tmp + 1) ^3 then count := count + 1 ; return count (lambda (n) (let ((cube (lambda (n) (expt n 3))) (cube-root (lambda (n) (inexact-&gt;exact (expt n 1/3))))) (let iter ((i 1) (count 0)) (if (&gt; (+ (expt i 3) 1) (/ n 2)) count (let* ((cube-i (cube i)) (tmp (floor (cube-root (- n cube-i))))) (iter (+ i 1) (+ count (if (or (= n (+ cube-i (cube tmp))) (= n (+ cube-i (cube (+ tmp 1))))) 1 0)))))))))) (let iter ((n 1)) (if (= (how-many-sum-of-2-positive-cubes n) 2) n (iter (+ 1 n)))))) </code></pre>

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<p>The objective was the following to be solved in Python:</p> <blockquote> <p>Given a string, def a function that returns another string with the vowels (upper or lowercase) replaced by 0,1,2,3,4 respectively.</p> <hr> <p>Example input:</p> <pre><code>"bB nN aei ou AEIOU" </code></pre> <p>Desired Output:</p> <pre><code>"bB nN 012 34 01234" </code></pre> <hr> </blockquote> <p>This is in fact quite trivial and can be solved in several ways, one way may be this:</p> <pre><code>def crypt(s): vow = ["a","e","i","o","u"] stringL = [] for x in s: if x in vow or x.lower() in vow: stringL.append(str(vow.index(x.lower()))) else: stringL.append(x) return "".join(stringL) </code></pre> <p>I was told this was over-complicated for such a simple task, that code like this would be difficult to debug etc.</p> <p>Would you consider this approach a "bad" one, which way would you have gone instead, is it unclear?</p>

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<p>I have been using the following function (in the kohana html class in a table) to generate tables.</p> <pre><code>function table($columns,$reverse=false,$fill=false,array $attr=null){ $c = ''; //ugly hack, looking for fix $max=sizeof(max($columns)); for($i=0;$i&lt;sizeof($columns);$i++){ $column = $columns[$i]; if($fill==true){ $l = ($max-sizeof($column)); for($ii=0;$ii&lt;$l;$ii++){ array_push($column,''); } } if($reverse==true){ $columns[$i] = array_reverse($column); }else{ $columns[$i] = $column; } } for($i=0,$l=sizeof($columns);$i&lt;$l;$i++){ $column = $columns[$i]; $c.="&lt;tr&gt;"; for($ii=0,$ll=sizeof($column);$ii&lt;$ll;$ii++){ $c.="&lt;td&gt;".$column[$ii]."&lt;/td&gt;"; } $c.="&lt;/tr&gt;"; } return "&lt;table".html::attributes($attr)."&gt;".$c."&lt;/table&gt;"; } </code></pre> <p>And then I have been calling it like so:</p> <pre><code>echo html::table(array( array('colunm 1 row 1','colunm 2 row 1'), )); </code></pre> <p>And a reversed table that auto fills the columns.</p> <pre><code>echo html::table(array( array('colunm 1 row 1','colunm 2 row 1'), array('column 1 row 2','column 2 row 2') ),true,true); </code></pre>

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<p>In the situation where I am looping through a collection looking for an item, is it better practice to <code>break</code> before I <code>return</code> or should I <code>break</code> and then <code>return</code>?</p> <p>Return during loop:</p> <pre><code>foreach(string item in items) { string[] split = item.Split('|'); if(split[0] == searchFor) return split[1]; } return null; </code></pre> <p>Break then return:</p> <pre><code>string result = null; foreach(string item in items) { string[] split = item.Split('|'); if(split[0] == searchFor) { result = split[1]; break; } } return result; </code></pre>

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<p>I managed to get something up and running, but I've no idea whether there are better ways to do this. I've spent all morning trying to figure out the best way to use parameters (allowing objects from the pipeline, or to be passed in, allowing overriding the <code>modelName</code>, etc.) and trying to understand differences between a Cmdlet and just a function, so feedback in that area in particular would be good.</p> <p><a href="http://code.dantup.com/PSRazor" rel="noreferrer">Bitbucket</a></p> <pre><code>function Format-Razor() { &lt;# .SYNOPSIS Formats a set of objects using the Razor Engine. .DESCRIPTION The Format-Razor function formats a set of objects using a supplied template using the Razor Engine created for ASP.NET. .NOTES Author: Danny Tuppeny (DanTup) .LINK http://code.dantup.com/PSRazor .PARAMETER templateText The Razor template text to be processed for each object. .PARAMETER modelName The name to use for access the data object in the template. Defaults to "Model". .EXAMPLE Get-Command | Select -Last 10 | Format-Razor "Command name: @Model.Name Loop: @for (int i = 0; i &lt; 5; i++) { &lt;y&gt;@i&lt;/y&gt; }" .EXAMPLE Get-Command | Select -Last 10 | Format-Razor "Command name: @Data.Name (@Data.CommandType)" -modelName "Data" .EXAMPLE Format-Razor "Command name: @Peter.Name Loop: @for (int i = 0; i &lt; 5; i++) { &lt;y&gt;@i&lt;/y&gt; }" $host -modelName "Peter" #&gt; [CmdletBinding()] PARAM( [Parameter(Mandatory=$true)] [string] $templateText, [Parameter(Mandatory=$true, ValueFromPipeline=$true)] [PSObject] $model, [Parameter(Mandatory=$false)] [string] $modelName = "Model" ) BEGIN { # Load the MVC assembly so we can access the Razor classes [System.Reflection.Assembly]::LoadWithPartialName("System.Web.Razor") | Out-Null # Create a StringReader for the template, which we'll need to pass into the Razor Engine $stringReader = New-Object System.IO.StringReader($templateText) $engine = CreateRazorTemplateEngine $razorResult = $engine.GenerateCode($stringReader) $results = CompileCode($razorResult); # If the template doesn't compile, we can't continue if ($results.Errors.HasErrors) { throw $results.Errors } # Create an instance of the Razor-generated template class that will be used in PROCESS for formatting $template = CreateTemplateInstance($results) } PROCESS { # Set the model to the current object, using the $modelName param so the user can customise it $template.$modelName = $model # Execute the code, which writes the output to our buffer $template.Execute() # "Return" the output for this item $template.Buffer.ToString() # Clear the buffer ready for the next object $template.Buffer.Clear() | Out-Null } } # Export the fuction for use by the user Export-ModuleMember -Function Format-Razor function CreateRazorTemplateEngine() { # Create an instance of the Razor engine for C# $language = New-Object System.Web.Razor.CSharpRazorCodeLanguage $host = New-Object System.Web.Razor.RazorEngineHost($language) # Set some default properties for the Razor-generated class $host.DefaultBaseClass = "TemplateBase" # This is our base class (created below) $host.DefaultNamespace = "RazorOutput" $host.DefaultClassName = "Template" # Add any default namespaces that will be useful to use in the templates $host.NamespaceImports.Add("System") | Out-Null New-Object System.Web.Razor.RazorTemplateEngine($host) } function CompileCode($razorResult) { # HACK: To avoid shipping a DLL, we're going to just compile our TemplateBase class here $baseClass = @" using System.IO; using System.Text; public abstract class TemplateBase { public StringBuilder Buffer { get; set; } public StringWriter Writer { get; set; } public dynamic $modelName { get; set; } public TemplateBase() { this.Buffer = new StringBuilder(); this.Writer = new StringWriter(this.Buffer); } public abstract void Execute(); public virtual void Write(object value) { WriteLiteral(value); } public virtual void WriteLiteral(object value) { Buffer.Append(value); } } "@ # Set up the compiler params, including any references required for the compilation $codeProvider = New-Object Microsoft.CSharp.CSharpCodeProvider $assemblies = @( [System.Reflection.Assembly]::LoadWithPartialName("System.Core").CodeBase.Replace("file:///", ""), [System.Reflection.Assembly]::LoadWithPartialName("Microsoft.CSharp").CodeBase.Replace("file:///", "") ) $compilerParams = New-Object System.CodeDom.Compiler.CompilerParameters(,$assemblies) # Compile the template base class $templateBaseResults = $codeProvider.CompileAssemblyFromSource($compilerParams, $baseClass); # Add the (just-generated) template base assembly to the compile parameters $assemblies = $assemblies + $templateBaseResults.CompiledAssembly.CodeBase.Replace("file:///", "") $compilerParams = New-Object System.CodeDom.Compiler.CompilerParameters(,$assemblies) # Compile the Razor-generated code $codeProvider.CompileAssemblyFromDom($compilerParams, $razorResult.GeneratedCode) } function CreateTemplateInstance($results) { # Grab the assembly that contains the Razor-generated classes $assembly = $results.CompiledAssembly # Create an instance of our Razor-generated class (this name is hard-coded above) $type = $assembly.GetType("RazorOutput.Template") [System.Activator]::CreateInstance($type) } </code></pre>

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<p>I've never been satisfied with any of the possible <code>sprintf()</code>-like functions in C++:</p> <ul> <li><code>sprintf()</code> is a C function and it's very unsafe and dangerous to use (undefined behavior all over the place)</li> <li><code>boost::format</code> is too slow and awkward to use (think of the <code>%</code> syntax)</li> <li><code>iostream</code> is <strong>extremely</strong> awkward to use</li> </ul> <p>So I came up with my own. Those are my requirements:</p> <ul> <li>Inspired by C#'s format function</li> <li>Must never fail at run time, never crash and never have undefined behavior, no matter what you call it with. Should fail at compile time whenever possible instead.</li> <li>Must be expandable (if you create a class <code>Person</code>, then you can pass a <code>Person</code> object to the function)</li> <li>Must be fast</li> <li>The format string must be easy to localize</li> <li>The format string must not have placeholders whose syntax depends on the argument type (ie, no <code>%s</code> vs <code>%d</code>)</li> <li>Must have a fairly "normal" syntax (no % like boost::format)</li> </ul> <p>I'm interested in reviews on the satisfaction of the requirements above. I'm especially interested in reviews from the end-user perspective and less about the internals of the code (i.e., the code that is hidden from the end user).</p> <p>A few examples:</p> <pre><code>// Returns a string containing "Hello my name is Andreas and I'm 22 years old". Format("Hello my name is {0} and I'm {1} years old.", "Andreas", 22); // Returns "Hex: 0xA" Format("Hex: {0:x}", 10); // Fails to compile: Person is not a built in type and doesn't have any function to convert to string struct Person {}; Person p; Format("Person: {0}", p); // "Person: Andreas Bonini" [Note: if it was {0:abc}, then Person::ToString("abc") would have been called] struct Person { Person(string first, string last) : First(first), Last(last) {} string ToString(const string &amp;options) const { return Format("{0} {1}", First, Last); } string First, Last; }; Person p("Andreas", "Bonini"); Format("Person: {0}", p); </code></pre> <p>These are my unit tests:</p> <pre><code>TEST(Format) { CHECK_EQUAL(Format("Testing {0} test {0}{0} test", 123), "Testing 123 test 123123 test"); CHECK_EQUAL(Format("{0}", (const char *)NULL), "{null}"); CHECK_EQUAL(Format("Test double {0} - {1}", 0, 1), "Test double 0 - 1"); CHECK_EQUAL(Format("Test options: {0:x}", 0xABC), "Test options: 0xABC"); CHECK_EQUAL(Format("Test malformed: {0:x", 0xABC), "Test malformed: {0:x"); CHECK_EQUAL(Format("Check stupid: {0:bmkldmbkglmbgk902 r iko4om wkl lfs s,gf, gfsdg fsd ! @ G}", "stupid"), "Check stupid: stupid"); CHECK_EQUAL(Format("Check missing: {1}", 0), "Check missing: {Argument 1}"); CHECK_EQUAL(Format("Master format test {0} {1} {2 {2:2} {3} {4:e} {5:x} {0}", 0, 1234.55566f, 1.11111f, "lolz", "a'b", 0xABCDEFABCDEFULL), "Master format test 0 1234.56 {2 1.11 lolz 'a\\'b' 0xABCDEFABCDEF 0"); CHECK_EQUAL(Format("{0:x}", 0xFFFFFFFF), "0xFFFFFFFF"); } </code></pre> <p>Note that due to C++ limitations (lack of variadic templates) the code isn't exactly pretty. Also the code is part of a bigger library so it won't compile of its own.</p> <pre><code>/**************************************************************************************** * Prism * File Name: Format.h * Added on: 2010/09/26 14:09:52 */ /***************************************************************************************/ #pragma once #include &lt;boost/type_traits.hpp&gt; /***************************************************************************************/ /* This is the main formatting function; it is 100% type safe and hopefully fast. It's inspired * by C#'s String.Format() function and has pretty much the base syntax: * * string format = Format("Hello {0}, my name is {1}.", "you", "me"); * * More precisely the placeholder can be: * {n[,a][:o]} * * n = Number of argument, starting from 0 * a = Alignment; if it's positive it is right aligned, otherwise left aligned * o = Options * * The arguments themselves to the conversion and handle the options. For each passed argument the * .ToString(options) function will be called, and the returned value will be used for replacing the * placeholder. * * Of course this won't work with built in types such as int. The conversion for those is implemented * in the library, which supports the following types (and options). * * The 'a' option means alternative. * * -- bool -- * - No options: prints "true" or "false". * - a: prints "yes" or "no". * * -- char -- * - No options: prints the character normally * - a: prints the character as a number. * * -- short, int, long -- * - No options: prints the number normally * - b: prints the number as binary * - x: prints the number as hex, prepending "0x" * - X: prints the number as hex, without "0x" * - ,: prints the number with a comma as thousands separator * * -- float, double -- * - No options: prints the number normally * - A number (N): equivalent to %.Nf * - %: multiplies by 100, adds a % sign * * -- string -- * - No options: prints the string normally * - e: Escapes the string for use in MySQL queries. * * &gt;&gt;&gt; Error handling &lt;&lt;&lt; * - Not enough arguments: FATAL() is called * - Too many arguments: not an error; extra arguments are ignored * - Unknown options: not an error; unknown options may not be implemented yet */ /***************************************************************************************/ namespace Prism { namespace Text { namespace Conversion { template&lt;class T&gt; string IntToString(T _val, bool hasSign, const string &amp;options) { typename boost::make_signed&lt;T&gt;::type valSigned = _val; typename boost::make_unsigned&lt;T&gt;::type valUnsigned = _val; if(options == ",") return GetCommaNumber(hasSign ? valSigned : valUnsigned); static const char itoa_tab[10] = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9' }; static const char xtoa_tab[16] = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F' }; static const char btoa_tab[2] = { '0', '1' }; int base; string ret; const char *tab; char tmp[128]; char *ptr = &amp;tmp[sizeof(tmp) - 1]; *ptr = 0; /* Parse options, set up variables */ if (options == "b") { base = 2; ret.reserve(64 + 1); hasSign = false; tab = btoa_tab; } else if (options == "x") { base = 16; ret.reserve(16 + 2 + 1); ret.push_back('0'); ret.push_back('x'); hasSign = false; tab = xtoa_tab; } else if (options == "X") { base = 16; ret.reserve(16 + 2); hasSign = false; tab = xtoa_tab; } else { base = 10; ret.reserve(22); tab = itoa_tab; } /* If it's negative */ if(hasSign &amp;&amp; valSigned &lt; 0) { ret.push_back('-'); valSigned = Math::Abs(valSigned); valUnsigned = valSigned; } do { *--ptr = tab[valUnsigned % base]; valUnsigned /= base; } while (valUnsigned); while(*ptr) ret.push_back(*ptr++); return ret; } inline string ToString(const char *s, const string &amp;options) { if(!s) s = "{null}"; if(options == "e") return SqlSafeCopy(s); return s; } inline string ToString(char *s, const string &amp;options) { return ToString((const char *)s, options); } template&lt;typename T&gt; string ToString(const T &amp;val, const string &amp;options) { return val.ToString(options); } template&lt;&gt; string ToString(const char &amp;val, const string &amp;options); template&lt;&gt; string ToString(const bool &amp;val, const string &amp;options); template&lt;&gt; string ToString(const float &amp;val, const string &amp;options); template&lt;&gt; string ToString(const double &amp;val, const string &amp;options); template&lt;&gt; inline string ToString(const int64 &amp;val, const string &amp;options) { return IntToString(val, true, options); } template&lt;&gt; inline string ToString(const uint64 &amp;val, const string &amp;options) { return IntToString(val, false, options); } template&lt;&gt; inline string ToString(const int32 &amp;val, const string &amp;options) { return IntToString(val, true, options); } template&lt;&gt; inline string ToString(const uint32 &amp;val, const string &amp;options) { return IntToString(val, false, options); } template&lt;&gt; inline string ToString(const int16 &amp;val, const string &amp;options) { return IntToString(val, true, options); } template&lt;&gt; inline string ToString(const uint16 &amp;val, const string &amp;options) { return IntToString(val, false, options); } template&lt;&gt; inline string ToString(const float &amp;val, const string &amp;options) { return ToString(static_cast&lt;double&gt;(val), options); } template&lt;&gt; inline string ToString(const string &amp;s, const string &amp;options) { if(options == "e") return SqlSafeCopy(s); return s; } } } } /***************************************************************************************/ namespace Prism { namespace Text { struct PlaceholderData { PlaceholderData(int start, int end, const string &amp;argument, int &amp;final_length) : Start(start), End(end), Argument(argument) { final_length = final_length - (End - Start) + Argument.length(); } int Start; int End; string Argument; }; extern string _FinalizeFormat(const string &amp;str, const vector&lt;PlaceholderData&gt; &amp;placeholders, int final_length); extern bool _FindPlaceholder(const char *str, int &amp;start, const int &amp;end, int &amp;num, int &amp;placeholder_length, string &amp;options); #include "FormatNoVariadicTemplates.h" } } /***************************************************************************************/ </code></pre> <pre><code>/**************************************************************************************** * Prism * File Name: Format.cpp * Added on: 2010/09/26 14:56:35 */ /***************************************************************************************/ #include "Prism.h" #include "Format.h" #include "Text.h" #if COMPILER == COMPILER_MSVC #pragma warning (disable: 4996) #endif namespace Prism { namespace Text { /***************************************************************************************/ namespace Conversion { template&lt;&gt; string ToString(const char &amp;val, const string &amp;options) { const bool alternative = (options == "a"); if (!alternative) return string(1, val); else return ToString((int)val, ""); } template&lt;&gt; string ToString(const bool &amp;val, const string &amp;options) { static const char *normalStrings[] = { "true", "false" }; static const char *alternativeStrings[] = { "yes", "no" }; const bool alternative = (options == "a"); const char **strings = alternative ? alternativeStrings : normalStrings; if (val) return strings[0]; else return strings[1]; } template&lt;&gt; string ToString(const double &amp;val, const string &amp;options) { if (options[0] == '%') return ToString(val * 100, options.substr(1)) + "%"; char ret[128]; if (IsDigit(options[0]) &amp;&amp; !options[1]) { char format[5]; format[0] = '%'; format[1] = '.'; format[2] = options[0]; format[3] = 'f'; format[4] = '\0'; sprintf(ret, format, val); } else sprintf(ret, "%g", val); return ret; } } /***************************************************************************************/ string _FinalizeFormat(const string &amp;str, const vector&lt;PlaceholderData&gt; &amp;placeholders, int final_length) { if(placeholders.empty()) return str; string ret; ret.reserve(final_length); int current_position = 0; const char *ptr = str.data(); foreach (const PlaceholderData &amp;placeholder, placeholders) { if (placeholder.Start != current_position) { const int bytes = (placeholder.Start - current_position); ret.append(ptr + current_position, bytes); current_position += bytes; } ret.append(placeholder.Argument); current_position += (placeholder.End - placeholder.Start); } const int remaining_bytes = str.size() - current_position; if (remaining_bytes &gt; 0) ret.append(ptr + current_position, remaining_bytes); return ret; } /***************************************************************************************/ static bool ReadPlaceholder(const char *str, int &amp;start, const int &amp;end, int &amp;num, int &amp;placeholder_length, string &amp;options) { const char *placeholder_number = &amp;str[start + 1]; char *endStr; if (!IsDigit(*placeholder_number)) return false; num = strtoul(placeholder_number, &amp;endStr, 10); if (!endStr) return false; if (*endStr == ':') { /* Read options */ ++endStr; const char *begin = endStr; while (endStr &lt; &amp;str[end] &amp;&amp; *endStr != '}') ++endStr; if (endStr == &amp;str[end]) return false; options.assign(begin, endStr - begin); } else options = ""; if (*endStr != '}') return false; ++endStr; placeholder_length = endStr - &amp;str[start]; return true; } /***************************************************************************************/ bool _FindPlaceholder(const char *str, int &amp;start, const int &amp;end, int &amp;num, int &amp;placeholder_length, string &amp;options) { /* Find the '{' */ for (int i = start; i &lt; end; ++i) { if (str[i] != '{') continue; /* Check if there is enough space for the minimum spaceholder length, 3: {.} */ if (end - i &lt; 3) continue; if (ReadPlaceholder(str, i, end, num, placeholder_length, options)) { start = i; return true; } } /* If we reach here, we reached the end of the string */ start = end; return false; } /***************************************************************************************/ } } </code></pre> <pre><code>/**************************************************************************************** * Prism * File Name: FormatNoVariadicTemplates.h * Added on: 2010/09/26 21:04:33 */ /***************************************************************************************/ #pragma once /***************************************************************************************/ /* Here we go.. */ #define FNVT_BEGIN vector&lt;PlaceholderData&gt; placeholders; \ int final_length = str.length(); \ int start = 0; \ const int end = str.length(); \ int num, placeholder_length; \ string argument, options; \ while (start &lt; end) { \ if (!_FindPlaceholder(str.c_str(), start, end, num, placeholder_length, options)) \ continue; \ switch(num) { #define FNVT_END default: \ argument = Format("{Argument {0}}", num); \ break; \ } \ placeholders.push_back(PlaceholderData(start, start + placeholder_length, argument, final_length)); \ start += placeholder_length; \ } \ return _FinalizeFormat(str, placeholders, final_length); #define ARGUMENT(n) case n: \ argument = Conversion::ToString(_ ## n, options); \ break; \ /***************************************************************************************/ template&lt;typename A&gt; string Format(const string &amp;str, const A &amp;_0) { FNVT_BEGIN; ARGUMENT(0); FNVT_END; } template&lt;typename A, typename B&gt; string Format(const string &amp;str, const A &amp;_0, const B &amp;_1) { FNVT_BEGIN; ARGUMENT(0); ARGUMENT(1); FNVT_END; } template&lt;typename A, typename B, typename C&gt; string Format(const string &amp;str, const A &amp;_0, const B &amp;_1, const C &amp;_2) { FNVT_BEGIN; ARGUMENT(0); ARGUMENT(1); ARGUMENT(2); FNVT_END; } template&lt;typename A, typename B, typename C, typename D&gt; string Format(const string &amp;str, const A &amp;_0, const B &amp;_1, const C &amp;_2, const D &amp;_3) { FNVT_BEGIN; ARGUMENT(0); ARGUMENT(1); ARGUMENT(2); ARGUMENT(3); FNVT_END; } template&lt;typename A, typename B, typename C, typename D, typename E&gt; string Format(const string &amp;str, const A &amp;_0, const B &amp;_1, const C &amp;_2, const D &amp;_3, const E &amp;_4) { FNVT_BEGIN; ARGUMENT(0); ARGUMENT(1); ARGUMENT(2); ARGUMENT(3); ARGUMENT(4); FNVT_END; } template&lt;typename A, typename B, typename C, typename D, typename E, typename F&gt; string Format(const string &amp;str, const A &amp;_0, const B &amp;_1, const C &amp;_2, const D &amp;_3, const E &amp;_4, const F &amp;_5) { FNVT_BEGIN; ARGUMENT(0); ARGUMENT(1); ARGUMENT(2); ARGUMENT(3); ARGUMENT(4); ARGUMENT(5); FNVT_END; } template&lt;typename A, typename B, typename C, typename D, typename E, typename F, typename G&gt; string Format(const string &amp;str, const A &amp;_0, const B &amp;_1, const C &amp;_2, const D &amp;_3, const E &amp;_4, const F &amp;_5, const G &amp;_6) { FNVT_BEGIN; ARGUMENT(0); ARGUMENT(1); ARGUMENT(2); ARGUMENT(3); ARGUMENT(4); ARGUMENT(5); ARGUMENT(6); FNVT_END; } template&lt;typename A, typename B, typename C, typename D, typename E, typename F, typename G, typename H&gt; string Format(const string &amp;str, const A &amp;_0, const B &amp;_1, const C &amp;_2, const D &amp;_3, const E &amp;_4, const F &amp;_5, const G &amp;_6, const H &amp;_7) { FNVT_BEGIN; ARGUMENT(0); ARGUMENT(1); ARGUMENT(2); ARGUMENT(3); ARGUMENT(4); ARGUMENT(5); ARGUMENT(6); ARGUMENT(7); FNVT_END; } template&lt;typename A, typename B, typename C, typename D, typename E, typename F, typename G, typename H, typename I&gt; string Format(const string &amp;str, const A &amp;_0, const B &amp;_1, const C &amp;_2, const D &amp;_3, const E &amp;_4, const F &amp;_5, const G &amp;_6, const H &amp;_7, const I &amp;_8) { FNVT_BEGIN; ARGUMENT(0); ARGUMENT(1); ARGUMENT(2); ARGUMENT(3); ARGUMENT(4); ARGUMENT(5); ARGUMENT(6); ARGUMENT(7); ARGUMENT(8); FNVT_END; } template&lt;typename A, typename B, typename C, typename D, typename E, typename F, typename G, typename H, typename I, typename J&gt; string Format(const string &amp;str, const A &amp;_0, const B &amp;_1, const C &amp;_2, const D &amp;_3, const E &amp;_4, const F &amp;_5, const G &amp;_6, const H &amp;_7, const I &amp;_8, const J &amp;_9) { FNVT_BEGIN; ARGUMENT(0); ARGUMENT(1); ARGUMENT(2); ARGUMENT(3); ARGUMENT(4); ARGUMENT(5); ARGUMENT(6); ARGUMENT(7); ARGUMENT(8); ARGUMENT(9); FNVT_END; } template&lt;typename A, typename B, typename C, typename D, typename E, typename F, typename G, typename H, typename I, typename J, typename K&gt; string Format(const string &amp;str, const A &amp;_0, const B &amp;_1, const C &amp;_2, const D &amp;_3, const E &amp;_4, const F &amp;_5, const G &amp;_6, const H &amp;_7, const I &amp;_8, const J &amp;_9, const K &amp;_10) { FNVT_BEGIN; ARGUMENT(0); ARGUMENT(1); ARGUMENT(2); ARGUMENT(3); ARGUMENT(4); ARGUMENT(5); ARGUMENT(6); ARGUMENT(7); ARGUMENT(8); ARGUMENT(9); ARGUMENT(10); FNVT_END; } template&lt;typename A, typename B, typename C, typename D, typename E, typename F, typename G, typename H, typename I, typename J, typename K, typename L&gt; string Format(const string &amp;str, const A &amp;_0, const B &amp;_1, const C &amp;_2, const D &amp;_3, const E &amp;_4, const F &amp;_5, const G &amp;_6, const H &amp;_7, const I &amp;_8, const J &amp;_9, const K &amp;_10, const L &amp;_11) { FNVT_BEGIN; ARGUMENT(0); ARGUMENT(1); ARGUMENT(2); ARGUMENT(3); ARGUMENT(4); ARGUMENT(5); ARGUMENT(6); ARGUMENT(7); ARGUMENT(8); ARGUMENT(9); ARGUMENT(10); ARGUMENT(11); FNVT_END; } template&lt;typename A, typename B, typename C, typename D, typename E, typename F, typename G, typename H, typename I, typename J, typename K, typename L, typename M&gt; string Format(const string &amp;str, const A &amp;_0, const B &amp;_1, const C &amp;_2, const D &amp;_3, const E &amp;_4, const F &amp;_5, const G &amp;_6, const H &amp;_7, const I &amp;_8, const J &amp;_9, const K &amp;_10, const L &amp;_11, const M &amp;_12) { FNVT_BEGIN; ARGUMENT(0); ARGUMENT(1); ARGUMENT(2); ARGUMENT(3); ARGUMENT(4); ARGUMENT(5); ARGUMENT(6); ARGUMENT(7); ARGUMENT(8); ARGUMENT(9); ARGUMENT(10); ARGUMENT(11); ARGUMENT(12); FNVT_END; } template&lt;typename A, typename B, typename C, typename D, typename E, typename F, typename G, typename H, typename I, typename J, typename K, typename L, typename M, typename N&gt; string Format(const string &amp;str, const A &amp;_0, const B &amp;_1, const C &amp;_2, const D &amp;_3, const E &amp;_4, const F &amp;_5, const G &amp;_6, const H &amp;_7, const I &amp;_8, const J &amp;_9, const K &amp;_10, const L &amp;_11, const M &amp;_12, const N &amp;_13) { FNVT_BEGIN; ARGUMENT(0); ARGUMENT(1); ARGUMENT(2); ARGUMENT(3); ARGUMENT(4); ARGUMENT(5); ARGUMENT(6); ARGUMENT(7); ARGUMENT(8); ARGUMENT(9); ARGUMENT(10); ARGUMENT(11); ARGUMENT(12); ARGUMENT(13); FNVT_END; } template&lt;typename A, typename B, typename C, typename D, typename E, typename F, typename G, typename H, typename I, typename J, typename K, typename L, typename M, typename N, typename O&gt; string Format(const string &amp;str, const A &amp;_0, const B &amp;_1, const C &amp;_2, const D &amp;_3, const E &amp;_4, const F &amp;_5, const G &amp;_6, const H &amp;_7, const I &amp;_8, const J &amp;_9, const K &amp;_10, const L &amp;_11, const M &amp;_12, const N &amp;_13, const O &amp;_14) { FNVT_BEGIN; ARGUMENT(0); ARGUMENT(1); ARGUMENT(2); ARGUMENT(3); ARGUMENT(4); ARGUMENT(5); ARGUMENT(6); ARGUMENT(7); ARGUMENT(8); ARGUMENT(9); ARGUMENT(10); ARGUMENT(11); ARGUMENT(12); ARGUMENT(13); ARGUMENT(14); FNVT_END; } template&lt;typename A, typename B, typename C, typename D, typename E, typename F, typename G, typename H, typename I, typename J, typename K, typename L, typename M, typename N, typename O, typename P&gt; string Format(const string &amp;str, const A &amp;_0, const B &amp;_1, const C &amp;_2, const D &amp;_3, const E &amp;_4, const F &amp;_5, const G &amp;_6, const H &amp;_7, const I &amp;_8, const J &amp;_9, const K &amp;_10, const L &amp;_11, const M &amp;_12, const N &amp;_13, const O &amp;_14, const P &amp;_15) { FNVT_BEGIN; ARGUMENT(0); ARGUMENT(1); ARGUMENT(2); ARGUMENT(3); ARGUMENT(4); ARGUMENT(5); ARGUMENT(6); ARGUMENT(7); ARGUMENT(8); ARGUMENT(9); ARGUMENT(10); ARGUMENT(11); ARGUMENT(12); ARGUMENT(13); ARGUMENT(14); ARGUMENT(15); FNVT_END; } template&lt;typename A, typename B, typename C, typename D, typename E, typename F, typename G, typename H, typename I, typename J, typename K, typename L, typename M, typename N, typename O, typename P, typename Q&gt; string Format(const string &amp;str, const A &amp;_0, const B &amp;_1, const C &amp;_2, const D &amp;_3, const E &amp;_4, const F &amp;_5, const G &amp;_6, const H &amp;_7, const I &amp;_8, const J &amp;_9, const K &amp;_10, const L &amp;_11, const M &amp;_12, const N &amp;_13, const O &amp;_14, const P &amp;_15, const Q &amp;_16) { FNVT_BEGIN; ARGUMENT(0); ARGUMENT(1); ARGUMENT(2); ARGUMENT(3); ARGUMENT(4); ARGUMENT(5); ARGUMENT(6); ARGUMENT(7); ARGUMENT(8); ARGUMENT(9); ARGUMENT(10); ARGUMENT(11); ARGUMENT(12); ARGUMENT(13); ARGUMENT(14); ARGUMENT(15); ARGUMENT(16); FNVT_END; } template&lt;typename A, typename B, typename C, typename D, typename E, typename F, typename G, typename H, typename I, typename J, typename K, typename L, typename M, typename N, typename O, typename P, typename Q, typename R&gt; string Format(const string &amp;str, const A &amp;_0, const B &amp;_1, const C &amp;_2, const D &amp;_3, const E &amp;_4, const F &amp;_5, const G &amp;_6, const H &amp;_7, const I &amp;_8, const J &amp;_9, const K &amp;_10, const L &amp;_11, const M &amp;_12, const N &amp;_13, const O &amp;_14, const P &amp;_15, const Q &amp;_16, const R &amp;_17) { FNVT_BEGIN; ARGUMENT(0); ARGUMENT(1); ARGUMENT(2); ARGUMENT(3); ARGUMENT(4); ARGUMENT(5); ARGUMENT(6); ARGUMENT(7); ARGUMENT(8); ARGUMENT(9); ARGUMENT(10); ARGUMENT(11); ARGUMENT(12); ARGUMENT(13); ARGUMENT(14); ARGUMENT(15); ARGUMENT(16); ARGUMENT(17); FNVT_END; } template&lt;typename A, typename B, typename C, typename D, typename E, typename F, typename G, typename H, typename I, typename J, typename K, typename L, typename M, typename N, typename O, typename P, typename Q, typename R, typename S&gt; string Format(const string &amp;str, const A &amp;_0, const B &amp;_1, const C &amp;_2, const D &amp;_3, const E &amp;_4, const F &amp;_5, const G &amp;_6, const H &amp;_7, const I &amp;_8, const J &amp;_9, const K &amp;_10, const L &amp;_11, const M &amp;_12, const N &amp;_13, const O &amp;_14, const P &amp;_15, const Q &amp;_16, const R &amp;_17, const S &amp;_18) { FNVT_BEGIN; ARGUMENT(0); ARGUMENT(1); ARGUMENT(2); ARGUMENT(3); ARGUMENT(4); ARGUMENT(5); ARGUMENT(6); ARGUMENT(7); ARGUMENT(8); ARGUMENT(9); ARGUMENT(10); ARGUMENT(11); ARGUMENT(12); ARGUMENT(13); ARGUMENT(14); ARGUMENT(15); ARGUMENT(16); ARGUMENT(17); ARGUMENT(18); FNVT_END; } template&lt;typename A, typename B, typename C, typename D, typename E, typename F, typename G, typename H, typename I, typename J, typename K, typename L, typename M, typename N, typename O, typename P, typename Q, typename R, typename S, typename T&gt; string Format(const string &amp;str, const A &amp;_0, const B &amp;_1, const C &amp;_2, const D &amp;_3, const E &amp;_4, const F &amp;_5, const G &amp;_6, const H &amp;_7, const I &amp;_8, const J &amp;_9, const K &amp;_10, const L &amp;_11, const M &amp;_12, const N &amp;_13, const O &amp;_14, const P &amp;_15, const Q &amp;_16, const R &amp;_17, const S &amp;_18, const T &amp;_19) { FNVT_BEGIN; ARGUMENT(0); ARGUMENT(1); ARGUMENT(2); ARGUMENT(3); ARGUMENT(4); ARGUMENT(5); ARGUMENT(6); ARGUMENT(7); ARGUMENT(8); ARGUMENT(9); ARGUMENT(10); ARGUMENT(11); ARGUMENT(12); ARGUMENT(13); ARGUMENT(14); ARGUMENT(15); ARGUMENT(16); ARGUMENT(17); ARGUMENT(18); ARGUMENT(19); FNVT_END; } template&lt;typename A, typename B, typename C, typename D, typename E, typename F, typename G, typename H, typename I, typename J, typename K, typename L, typename M, typename N, typename O, typename P, typename Q, typename R, typename S, typename T, typename U&gt; string Format(const string &amp;str, const A &amp;_0, const B &amp;_1, const C &amp;_2, const D &amp;_3, const E &amp;_4, const F &amp;_5, const G &amp;_6, const H &amp;_7, const I &amp;_8, const J &amp;_9, const K &amp;_10, const L &amp;_11, const M &amp;_12, const N &amp;_13, const O &amp;_14, const P &amp;_15, const Q &amp;_16, const R &amp;_17, const S &amp;_18, const T &amp;_19, const U &amp;_20) { FNVT_BEGIN; ARGUMENT(0); ARGUMENT(1); ARGUMENT(2); ARGUMENT(3); ARGUMENT(4); ARGUMENT(5); ARGUMENT(6); ARGUMENT(7); ARGUMENT(8); ARGUMENT(9); ARGUMENT(10); ARGUMENT(11); ARGUMENT(12); ARGUMENT(13); ARGUMENT(14); ARGUMENT(15); ARGUMENT(16); ARGUMENT(17); ARGUMENT(18); ARGUMENT(19); ARGUMENT(20); FNVT_END; } template&lt;typename A, typename B, typename C, typename D, typename E, typename F, typename G, typename H, typename I, typename J, typename K, typename L, typename M, typename N, typename O, typename P, typename Q, typename R, typename S, typename T, typename U, typename V&gt; string Format(const string &amp;str, const A &amp;_0, const B &amp;_1, const C &amp;_2, const D &amp;_3, const E &amp;_4, const F &amp;_5, const G &amp;_6, const H &amp;_7, const I &amp;_8, const J &amp;_9, const K &amp;_10, const L &amp;_11, const M &amp;_12, const N &amp;_13, const O &amp;_14, const P &amp;_15, const Q &amp;_16, const R &amp;_17, const S &amp;_18, const T &amp;_19, const U &amp;_20, const V &amp;_21) { FNVT_BEGIN; ARGUMENT(0); ARGUMENT(1); ARGUMENT(2); ARGUMENT(3); ARGUMENT(4); ARGUMENT(5); ARGUMENT(6); ARGUMENT(7); ARGUMENT(8); ARGUMENT(9); ARGUMENT(10); ARGUMENT(11); ARGUMENT(12); ARGUMENT(13); ARGUMENT(14); ARGUMENT(15); ARGUMENT(16); ARGUMENT(17); ARGUMENT(18); ARGUMENT(19); ARGUMENT(20); ARGUMENT(21); FNVT_END; } template&lt;typename A, typename B, typename C, typename D, typename E, typename F, typename G, typename H, typename I, typename J, typename K, typename L, typename M, typename N, typename O, typename P, typename Q, typename R, typename S, typename T, typename U, typename V, typename W&gt; string Format(const string &amp;str, const A &amp;_0, const B &amp;_1, const C &amp;_2, const D &amp;_3, const E &amp;_4, const F &amp;_5, const G &amp;_6, const H &amp;_7, const I &amp;_8, const J &amp;_9, const K &amp;_10, const L &amp;_11, const M &amp;_12, const N &amp;_13, const O &amp;_14, const P &amp;_15, const Q &amp;_16, const R &amp;_17, const S &amp;_18, const T &amp;_19, const U &amp;_20, const V &amp;_21, const W &amp;_22) { FNVT_BEGIN; ARGUMENT(0); ARGUMENT(1); ARGUMENT(2); ARGUMENT(3); ARGUMENT(4); ARGUMENT(5); ARGUMENT(6); ARGUMENT(7); ARGUMENT(8); ARGUMENT(9); ARGUMENT(10); ARGUMENT(11); ARGUMENT(12); ARGUMENT(13); ARGUMENT(14); ARGUMENT(15); ARGUMENT(16); ARGUMENT(17); ARGUMENT(18); ARGUMENT(19); ARGUMENT(20); ARGUMENT(21); ARGUMENT(22); FNVT_END; } template&lt;typename A, typename B, typename C, typename D, typename E, typename F, typename G, typename H, typename I, typename J, typename K, typename L, typename M, typename N, typename O, typename P, typename Q, typename R, typename S, typename T, typename U, typename V, typename W, typename X&gt; string Format(const string &amp;str, const A &amp;_0, const B &amp;_1, const C &amp;_2, const D &amp;_3, const E &amp;_4, const F &amp;_5, const G &amp;_6, const H &amp;_7, const I &amp;_8, const J &amp;_9, const K &amp;_10, const L &amp;_11, const M &amp;_12, const N &amp;_13, const O &amp;_14, const P &amp;_15, const Q &amp;_16, const R &amp;_17, const S &amp;_18, const T &amp;_19, const U &amp;_20, const V &amp;_21, const W &amp;_22, const X &amp;_23) { FNVT_BEGIN; ARGUMENT(0); ARGUMENT(1); ARGUMENT(2); ARGUMENT(3); ARGUMENT(4); ARGUMENT(5); ARGUMENT(6); ARGUMENT(7); ARGUMENT(8); ARGUMENT(9); ARGUMENT(10); ARGUMENT(11); ARGUMENT(12); ARGUMENT(13); ARGUMENT(14); ARGUMENT(15); ARGUMENT(16); ARGUMENT(17); ARGUMENT(18); ARGUMENT(19); ARGUMENT(20); ARGUMENT(21); ARGUMENT(22); ARGUMENT(23); FNVT_END; } template&lt;typename A, typename B, typename C, typename D, typename E, typename F, typename G, typename H, typename I, typename J, typename K, typename L, typename M, typename N, typename O, typename P, typename Q, typename R, typename S, typename T, typename U, typename V, typename W, typename X, typename Y&gt; string Format(const string &amp;str, const A &amp;_0, const B &amp;_1, const C &amp;_2, const D &amp;_3, const E &amp;_4, const F &amp;_5, const G &amp;_6, const H &amp;_7, const I &amp;_8, const J &amp;_9, const K &amp;_10, const L &amp;_11, const M &amp;_12, const N &amp;_13, const O &amp;_14, const P &amp;_15, const Q &amp;_16, const R &amp;_17, const S &amp;_18, const T &amp;_19, const U &amp;_20, const V &amp;_21, const W &amp;_22, const X &amp;_23, const Y &amp;_24) { FNVT_BEGIN; ARGUMENT(0); ARGUMENT(1); ARGUMENT(2); ARGUMENT(3); ARGUMENT(4); ARGUMENT(5); ARGUMENT(6); ARGUMENT(7); ARGUMENT(8); ARGUMENT(9); ARGUMENT(10); ARGUMENT(11); ARGUMENT(12); ARGUMENT(13); ARGUMENT(14); ARGUMENT(15); ARGUMENT(16); ARGUMENT(17); ARGUMENT(18); ARGUMENT(19); ARGUMENT(20); ARGUMENT(21); ARGUMENT(22); ARGUMENT(23); ARGUMENT(24); FNVT_END; } template&lt;typename A, typename B, typename C, typename D, typename E, typename F, typename G, typename H, typename I, typename J, typename K, typename L, typename M, typename N, typename O, typename P, typename Q, typename R, typename S, typename T, typename U, typename V, typename W, typename X, typename Y, typename Z&gt; string Format(const string &amp;str, const A &amp;_0, const B &amp;_1, const C &amp;_2, const D &amp;_3, const E &amp;_4, const F &amp;_5, const G &amp;_6, const H &amp;_7, const I &amp;_8, const J &amp;_9, const K &amp;_10, const L &amp;_11, const M &amp;_12, const N &amp;_13, const O &amp;_14, const P &amp;_15, const Q &amp;_16, const R &amp;_17, const S &amp;_18, const T &amp;_19, const U &amp;_20, const V &amp;_21, const W &amp;_22, const X &amp;_23, const Y &amp;_24, const Z &amp;_25) { FNVT_BEGIN; ARGUMENT(0); ARGUMENT(1); ARGUMENT(2); ARGUMENT(3); ARGUMENT(4); ARGUMENT(5); ARGUMENT(6); ARGUMENT(7); ARGUMENT(8); ARGUMENT(9); ARGUMENT(10); ARGUMENT(11); ARGUMENT(12); ARGUMENT(13); ARGUMENT(14); ARGUMENT(15); ARGUMENT(16); ARGUMENT(17); ARGUMENT(18); ARGUMENT(19); ARGUMENT(20); ARGUMENT(21); ARGUMENT(22); ARGUMENT(23); ARGUMENT(24); ARGUMENT(25); FNVT_END; } /***************************************************************************************/ </code></pre>

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<p>I am writing a wrapper for dynamic behavior in C#. If I use <code>GetMethod()</code>, then an exception is thrown when there is more than one method (overloads). I figure it will become apparent at runtime that if there is an argument mismatch anyway. Is this a good way to solve the problem?</p> <pre><code>public class StaticMembersDynamicWrapper : DynamicObject { private Type _type; public StaticMembersDynamicWrapper(Type type) { _type = type; } // Handle static methods public override bool TryInvokeMember(InvokeMemberBinder binder, object[] args, out object result) { var methods = _type .GetMethods(BindingFlags.FlattenHierarchy | BindingFlags.Static | BindingFlags.Public) .Where(methodInfo =&gt; methodInfo.Name == binder.Name); var method = methods.FirstOrDefault(); if (method != null) { result = method.Invoke(null, args); return true; } result = null; return false; } } </code></pre>

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<p>I am seeing it more and more.</p> <p>Which do you think works best and why?</p> <p>This:</p> <pre><code>$config = array( 'param1'=&gt;'abc' 'param2'=&gt;'dfg' ); new Class($config); </code></pre> <p>Or:</p> <pre><code>new Class('abc','dfg'); </code></pre>

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<p><a href="http://en.wikipedia.org/wiki/Trie" rel="noreferrer">http://en.wikipedia.org/wiki/Trie</a></p> <p>The basic idea is to support fast searches via prefix matching. In my implementation, I allow each node to store all of the words that match its given prefix, and then if the word length exceeds the length of the node's prefix, it passes the word into its children for further storage.</p> <pre><code>public class TrieNode { private string Prefix { get; set; } private IList&lt;string&gt; Items { get; set; } private IDictionary&lt;string, TrieNode&gt; ChildNodes { get; set; } private IEqualityComparer&lt;string&gt; Comparer { get; set; } public TrieNode() : this(StringComparer.CurrentCulture) { } public TrieNode(IEqualityComparer&lt;string&gt; comparer) : this(comparer, string.Empty) { } private TrieNode(IEqualityComparer&lt;string&gt; comparer, string prefix) { if (prefix == null) throw new ArgumentNullException("Invalid prefix"); this.Prefix = prefix; this.Items = new List&lt;string&gt;(); this.ChildNodes = new Dictionary&lt;string, TrieNode&gt;(comparer); this.Comparer = comparer; } public void Add(string word) { if (word == null) throw new InvalidOperationException("Cannot add null to list"); if (word.Length &lt; this.Prefix.Length || !this.Comparer.Equals(word.Substring(0, this.Prefix.Length), this.Prefix)) { throw new ArgumentException("Parameter does not match prefix."); } this.Items.Add(word); if (word.Length &gt; this.Prefix.Length) { string childKey = word.Substring(0, this.Prefix.Length + 1); if (!this.ChildNodes.ContainsKey(childKey)) { this.ChildNodes.Add(childKey, new TrieNode(this.Comparer, childKey)); } this.ChildNodes[childKey].Add(word); } } public void AddRange(IEnumerable&lt;string&gt; words) { foreach (string word in words) this.Add(word); } public ReadOnlyCollection&lt;string&gt; FindMatches(string searchPrefix) { if (searchPrefix == null) throw new InvalidOperationException("Cannot search on null strings"); if (this.Comparer.Equals(searchPrefix, this.Prefix)) { return new ReadOnlyCollection&lt;string&gt;(this.Items); } else { string childKey = searchPrefix.Substring(0, this.Prefix.Length + 1); if (this.ChildNodes.ContainsKey(childKey)) return this.ChildNodes[childKey].FindMatches(searchPrefix); else return new ReadOnlyCollection&lt;string&gt;(new string[0]); // empty list for no matches } } } </code></pre> <p>...</p> <pre><code>TrieNode trie = new TrieNode(StringComparer.CurrentCultureIgnoreCase); trie.AddRange(new string[] { "Apple", "Banana", "BANANA", "Bar", "Berry", "Cherry", "Coconut", "Date" }); ReadOnlyCollection&lt;string&gt; matches = trie.FindMatches("BA"); // BANANA, banana, Bar </code></pre> <p>The slight concern I have is that each node contains its list of matching words, it's not an aggregation from its children. I call it <em>slight</em>, because it allows for easy logic when performing searches, as once a match is found, there's no need to further poll children and aggregate responses. On the other hand, I end up storing the same word in <em>n</em> lists, where <em>n</em> is the length of the word. </p> <p><strong>Edit</strong> An answer suggested returning an <code>IEnumerable&lt;string&gt;</code> to allow lazy streaming of results as well as to eliminate unnecessary copying. The tradeoff is that ordering is not preserved<strike>, and the code logic (at least, the way I tried it) is a bit less simple</strike>. But the quick changes I made to allow such a sequence are the following. First, inside the <code>Add</code> method, only storing matches to the specific prefix </p> <pre><code>if (this.Comparer.Equals(word, this.Prefix)) { // keep each match - preserves number of matches as well as differences // if the comparer allows insensitive equality this.Items.Add(word); } </code></pre> <p>And then the <code>FindMatches</code> method</p> <pre><code>public IEnumerable&lt;string&gt; FindMatches(string searchPrefix) { if (searchPrefix == null) throw new InvalidOperationException("Cannot search on null strings"); if (this.Comparer.Equals(searchPrefix, this.Prefix)) { return this.Items.Concat(this.ChildNodes.SelectMany(n =&gt; n.Value.FindMatches(n.Key))); } else { string childKey = searchPrefix.Substring(0, this.Prefix.Length + 1); if (this.ChildNodes.ContainsKey(childKey)) { return this.ChildNodes[childKey].FindMatches(searchPrefix); } else { return Enumerable.Repeat(string.Empty, 0); } } } </code></pre>

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<p>I have this python code that compares merge sort and selection sort, but it is taking "forever."</p> <pre><code>import time import random # Selection Sort Code # def maxIndex(J): return J.index(max(J)) def swap(LCopy, i, j): temp = LCopy[i] LCopy[i] = LCopy[j] LCopy[j] = temp # Implementation of selection sort def selectionSort(L): for i in range(len(L)-1, 1, -1): j = maxIndex(L[0:i+1]) swap(L, i, j) # Merge Sort Code # # Assumes that L[first:mid+1] is sorted and also # that L[mid: last+1] is sorted. Returns L with L[first: last+1] sorted def merge(L, first, mid, last): i = first # index into the first half j = mid + 1 # index into the second half tempList = [] # This loops goes on as long as BOTH i and j stay within their # respective sorted blocks while (i &lt;= mid) and (j &lt;= last): if L[i] &lt;= L[j]: tempList.append(L[i]) #print L[i], "from the first block" i += 1 else: tempList.append(L[j]) #print L[j], "from the second block" j += 1 # If i goes beyond the first block, there may be some elements # in the second block that need to be copied into tempList. # Similarly, if j goes beyond the second block, there may be some # elements in the first block that need to be copied into tempList if i == mid + 1: tempList.extend(L[j:last+1]) #print L[j:last+1], "some elements in second block are left over" elif j == last+1: tempList.extend(L[i:mid+1]) #print L[i:mid+1], "some elements from first block are left over" L[first:last+1] = tempList #print tempList # The merge sort function; sorts the sublist L[first:last+1] def generalMergeSort(L, first, last): # Base case: if first == last then it is already sorted # Recursive case: L[first:last+1] has size 2 or more if first &lt; last: # divide step mid = (first + last)/2 # conquer step generalMergeSort(L, first, mid) generalMergeSort(L, mid+1, last) # combine step merge(L, first, mid, last) # Wrapper function def mergeSort(L): generalMergeSort(L, 0, len(L)-1) m = 10 n = 100000 n_increments = 9 baseList = [ random.randint(0,100) for r in range(n) ] i = 0 while i &lt; n_increments: j = 0 sel_time = 0 mer_time = 0 while j &lt; m: # Do a Selection Sort # x = time.clock() selectionSort( baseList) y = time.clock() sel_time += ( y - x ) random.shuffle( baseList ) # Do a Merge Sort # x = time.clock() mergeSort( baseList ) y = time.clock() mer_time += ( y - x ) random.shuffle( baseList ) j += 1 print "average select sort time for a list of", n, "size:", sel_time / m print "average merge sort time for a list of", n, "size:", mer_time / m j = 0 i += 1 n += 10000 </code></pre>

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<p>In order to avoid the user having to explicitly prefix a script with <code>sudo</code> or <code>su --command</code>, I wrote the following:</p> <pre><code>import sys import os if os.getuid(): root = "/usr/bin/sudo" if not os.path.exists("/usr/bin/sudo"): root = "/bin/su --command" command = "{} {}".format(root, sys.argv[0]) command = command.split() retcode = subprocess.call(command) if retcode: print("something wrong happened") else: action_that_needs_admin_rights() </code></pre> <p>It feels like a hack to me, so am looking forward to better approaches.</p>

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<p>Just for the heck of it, I wrote a simple little interpreter that takes in inputs in the form of Polish Notation.</p> <p>The user will input something like</p> <blockquote> <p><code>+ 5 6</code></p> </blockquote> <p>And it will then output</p> <blockquote> <p><code>11</code></p> </blockquote> <p>Here's another sample input:</p> <blockquote> <p><code>+ 5 * 2 3</code></p> </blockquote> <p>And the output:</p> <blockquote> <p><code>11</code></p> </blockquote> <p>Users can even define their own variables, like this:</p> <blockquote> <p><code>def myVar 10</code></p> </blockquote> <p>and like this:</p> <blockquote> <p><code>def anotherVar + 5 6</code></p> </blockquote> <p>And then of course reuse those variables. So let's say you type</p> <blockquote> <p><code>myVar</code></p> </blockquote> <p>it will ouput</p> <blockquote> <p><code>10</code></p> </blockquote> <p>or</p> <blockquote> <p><code>anotherVar</code></p> </blockquote> <p>which outputs</p> <blockquote> <p><code>11</code></p> </blockquote> <p>Furthermore, you type in</p> <blockquote> <p><code>+ myVar anotherVar</code></p> </blockquote> <p>you would then get</p> <blockquote> <p><code>21</code></p> </blockquote> <hr> <p>I'm a total newbie to well-formatted and readable code. What would be a good way to refactor this?</p> <pre><code>#include &lt;iostream&gt; #include &lt;vector&gt; #include &lt;string&gt; #include &lt;sstream&gt; using namespace std; class Variable { public: Variable(const string&amp; name, double val) { this-&gt;name = name; this-&gt;val = val; } inline const string&amp; get_name() const { return name; } inline double get_val() const { return val; } private: string name; double val; }; //---------------------------------- double operate(const string&amp; op, istringstream&amp; iss, vector&lt;Variable&gt;&amp; v); double perform_addition(istringstream&amp; iss, vector&lt;Variable&gt;&amp; v); double perform_subtraction(istringstream&amp; iss, vector&lt;Variable&gt;&amp; v); double perform_division(istringstream&amp; iss, vector&lt;Variable&gt;&amp; v); double perform_multiplication(istringstream&amp; iss, vector&lt;Variable&gt;&amp; v); void define_new_var(vector&lt;Variable&gt;&amp; v, istringstream&amp; iss); bool is_number(const string&amp; op) { int char_to_int = op[0]; if (char_to_int &gt;= 48 &amp;&amp; char_to_int &lt;= 57) return true; return false; } void print_var_list(vector&lt;Variable&gt;&amp; v) { int size = v.size(); for (int i = 0; i &lt; size; i++) { cout &lt;&lt; v[i].get_name() &lt;&lt; ", " &lt;&lt; v[i].get_val() &lt;&lt; endl; } cout &lt;&lt; endl; } int main() { cout &lt;&lt; endl &lt;&lt; "LeRPN Programming Language" &lt;&lt; endl; vector&lt;Variable&gt; v; string temp; while (cin) { cout &lt;&lt; endl &lt;&lt; "&gt; "; getline(cin, temp); istringstream iss(temp); string op; iss &gt;&gt; op; if (op == "quit") break; else if (op == "def") define_new_var(v, iss); else if (op == "show_vars") print_var_list(v); else cout &lt;&lt; endl &lt;&lt; operate(op, iss, v) &lt;&lt; endl; } } double perform_addition(istringstream&amp; iss, vector&lt;Variable&gt;&amp; v) { string left; iss &gt;&gt; left; string right; iss &gt;&gt; right; return operate(left, iss, v) + operate(right, iss, v); } double perform_subtraction(istringstream&amp; iss, vector&lt;Variable&gt;&amp; v) { string left; iss &gt;&gt; left; string right; iss &gt;&gt; right; return operate(left, iss, v) - operate(right, iss, v); } double perform_division(istringstream&amp; iss, vector&lt;Variable&gt;&amp; v) { string left; iss &gt;&gt; left; string right; iss &gt;&gt; right; return operate(left, iss, v) / operate(right, iss, v); } double perform_multiplication(istringstream&amp; iss, vector&lt;Variable&gt;&amp; v) { string left; iss &gt;&gt; left; string right; iss &gt;&gt; right; return operate(left, iss, v) * operate(right, iss, v); } double get_variable(const string&amp; op, vector&lt;Variable&gt;&amp; v) { int size = v.size(); for (int i = 0; i &lt; size; i++) { if (op == v[i].get_name()) return v[i].get_val(); } } double operate(const string&amp; op, istringstream&amp; iss, vector&lt;Variable&gt;&amp; v) { double value; if (op == "+") value = perform_addition(iss, v); else if (op == "-") value = perform_subtraction(iss, v); else if (op == "/") value = perform_division(iss, v); else if(op == "*") value = perform_multiplication(iss, v); else if (is_number(op)) value = atof(op.c_str()); else value = get_variable(op, v); return value; } void define_new_var(vector&lt;Variable&gt;&amp; v, istringstream&amp; iss) { string name; iss &gt;&gt; name; string temp; iss &gt;&gt; temp; double value = operate(temp, iss, v); v.push_back(Variable(name, value)); } </code></pre>

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<p>Is it good or bad practice (or, when is it appropriate) to use shorthand methods?</p> <p>Lets pretend we're using jQuery here, because it has a lot of them.:</p> <pre><code>jQuery.ajax() jQuery.get() jQuery.getJSON() jQuery.getScript() .load() jQuery.post() </code></pre> <p>These are all really just shorthand forms for the ajax function, with the exception of load which combines another function later on.</p> <p>I can use <code>$.ajax( dataType: 'script',)</code> to do the same thing as <code>getScript</code>, but why?</p> <p>This to me seems insane, and overly complicates the API. Is this good, or bad, or what? Why isn't there a getCSS and a PostCSS and a postScript and a putScript too?</p>

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