Module:String

This module is intended to provide access to basic string functions.

Most of the functions provided here can be invoked with named parameters, unnamed parameters, or a mixture. If named parameters are used, Mediawiki will automatically remove any leading or trailing whitespace from the parameter. Depending on the intended use, it may be advantageous to either preserve or remove such whitespace.

## Global options

ignore\_errors
If set to 'true' or 1, any error condition will result in an empty string being returned rather than an error message.
error\_category
If an error occurs, specifies the name of a category to include with the error message. The default category is Category:Errors reported by Module String.
no\_category
If set to 'true' or 1, no category will be added if an error is generated.
Unit tests for this module are available at Module:String/testcases.

## len

This function returns the length of the target string.

Usage:

`{{#invoke:String|len|*target\_string*}}`
OR

`{{#invoke:String|len|s= *target\_string* }}`
Parameters:

s
The string whose length to report
## sub

This function returns a substring of the target string at specified indices.
Usage:

OR

Parameters:

s
The string to return a subset of
i
The first index of the substring to return, defaults to 1.
j
The last index of the string to return, defaults to the last character.
The first character of the string is assigned an index of 1. If either i or j is a negative value, it is interpreted the same as selecting a character by counting from the end of the string. Hence, a value of -1 is the same as selecting the last character of the string.

If the requested indices are out of range for the given string, an error is reported.

## sublength

This function implements the features of {{Str sub old}} and is kept in order to maintain these older templates.

## match

This function returns a substring from the source string that matches a specified pattern.

Usage:

OR

Parameters:

s
The string to search
pattern
The pattern or string to find within the string
start
The index within the source string to start the search. The first character of the string has index 1. Defaults to 1.
match
In some cases it may be possible to make multiple matches on a single string. This specifies which match to return, where the first match is match= 1. If a negative number is specified then a match is returned counting from the last match. Hence match = -1 is the same as requesting the last match. Defaults to 1.
plain
A flag indicating that the pattern should be understood as plain text. Defaults to false.
nomatch
If no match is found, output the "nomatch" value rather than an error.
If the match\_number or start\_index are out of range for the string being queried, then this function generates an error. An error is also generated if no match is found.
If one adds the parameter ignore\_errors=true, then the error will be suppressed and an empty string will be returned on any failure.

For information on constructing Lua patterns, a form of regular expression, see:

* Lua reference: Patterns (as of version 5.1)
* Scribunto patterns
* Scribunto Unicode string patterns

## pos

This function returns a single character from the target string at position pos.

Usage:

`{{#invoke:String|pos|*target\_string*|*index\_value*}}`
OR

`{{#invoke:String|pos|target= *target\_string* |pos= *index\_value* }}`
Parameters:

target
The string to search
pos
The index for the character to return
The first character has an index value of 1.

If one requests a negative value, this function will select a character by counting backwards
from the end of the string. In other words pos = -1 is the same as asking for the last character.

A requested value of zero, or a value greater than the length of the string returns an error.

## find

This function allows one to search for a target string or pattern within another string.

Usage:

OR

Parameters:

source
The string to search
target
The string or pattern to find within source
start
The index within the source string to start the search, defaults to 1
plain
Boolean flag indicating that target should be understood as plain text and not as a Lua-style regular expression, defaults to true
This function returns the first index >= "start" where "target" can be found within "source". Indices are 1-based. If "target" is not found, then this function returns 0. If either "source" or "target" are missing / empty, this function also returns 0.

This function should be safe for UTF-8 strings.

## replace

This function allows one to replace a target string or pattern within another string.

Usage:

OR

Parameters:

source
The string to search
pattern
The string or pattern to find within source
replace
The replacement text
count
The number of occurrences to replace; defaults to all
plain
Boolean flag indicating that pattern should be understood as plain text and not as a Scribunto ustring pattern (a unicode-friendly Lua-style regular expression); defaults to true
## rep

Repeats a string *n* times. A simple function to pipe string.rep to templates.
Usage:

`{{#invoke:String|rep|*source*|*count*}}`
Parameters:

source
The string to repeat
count
The number of repetitions.
Example `{{#invoke:String|rep|hello|3}}` gives **Lua error at line 476: attempt to call local 'str' (a table value).**

```
--[[

This module is intended to provide access to basic string functions.

Most of the functions provided here can be invoked with named parameters,
unnamed parameters, or a mixture. If named parameters are used, Mediawiki will
automatically remove any leading or trailing whitespace from the parameter.
Depending on the intended use, it may be advantageous to either preserve or
remove such whitespace.

Global options
 ignore\_errors: If set to 'true' or 1, any error condition will result in
 an empty string being returned rather than an error message.

 error\_category: If an error occurs, specifies the name of a category to
 include with the error message. The default category is
 [Category:Errors reported by Module String].

 no\_category: If set to 'true' or 1, no category will be added if an error
 is generated.

Unit tests for this module are available at Module:String/tests.
]]

local str = {}

--[[
len

This function returns the length of the target string.

Usage:
{{#invoke:String|len|target\_string|}}
OR
{{#invoke:String|len|s=target\_string}}

Parameters
 s: The string whose length to report

If invoked using named parameters, Mediawiki will automatically remove any leading or
trailing whitespace from the target string.
]]
function str.len( frame )
 local new\_args = str.\_getParameters( frame.args, {'s'} );
 local s = new\_args['s'] or '';
 return mw.ustring.len( s )
end

--[[
sub

This function returns a substring of the target string at specified indices.

Usage:
OR

Parameters
 s: The string to return a subset of
 i: The fist index of the substring to return, defaults to 1.
 j: The last index of the string to return, defaults to the last character.

The first character of the string is assigned an index of 1. If either i or j
is a negative value, it is interpreted the same as selecting a character by
counting from the end of the string. Hence, a value of -1 is the same as
selecting the last character of the string.

If the requested indices are out of range for the given string, an error is
reported.
]]
function str.sub( frame )
 local new\_args = str.\_getParameters( frame.args, { 's', 'i', 'j' } );
 local s = new\_args['s'] or '';
 local i = tonumber( new\_args['i'] ) or 1;
 local j = tonumber( new\_args['j'] ) or -1;

 local len = mw.ustring.len( s );

 -- Convert negatives for range checking
 if i < 0 then
 i = len + i + 1;
 end
 if j < 0 then
 j = len + j + 1;
 end

 if j > len then
 j = len;
 end

 if i > len or i < 1 or j < 1 then
 return str.\_error( 'String subset index out of range' );
 end
 if j < i then
 return str.\_error( 'String subset indices out of order' );
 end

 return mw.ustring.sub( s, i, j )
end

--[[
This function implements that features of {{str sub old}} and is kept in order
to maintain these older templates.
]]
function str.sublength( frame )
 local i = tonumber( frame.args.i ) or 0
 local len = tonumber( frame.args.len )
 return mw.ustring.sub( frame.args.s, i + 1, len and ( i + len ) )
end

--[[
match

This function returns a substring from the source string that matches a
specified pattern.

Usage:
OR

Parameters
 s: The string to search
 pattern: The pattern or string to find within the string
 start: The index within the source string to start the search. The first
 character of the string has index 1. Defaults to 1.
 match: In some cases it may be possible to make multiple matches on a single
 string. This specifies which match to return, where the first match is
 match= 1. If a negative number is specified then a match is returned
 counting from the last match. Hence match = -1 is the same as requesting
 the last match. Defaults to 1.
 plain: A flag indicating that the pattern should be understood as plain
 text. Defaults to false.
 nomatch: If no match is found, output the "nomatch" value rather than an error.

If invoked using named parameters, Mediawiki will automatically remove any leading or
trailing whitespace from each string. In some circumstances this is desirable, in
other cases one may want to preserve the whitespace.

If the match\_number or start\_index are out of range for the string being queried, then
this function generates an error. An error is also generated if no match is found.
If one adds the parameter ignore\_errors=true, then the error will be suppressed and
an empty string will be returned on any failure.

For information on constructing Lua patterns, a form of [regular expression], see:

\* http://www.lua.org/manual/5.1/manual.html#5.4.1
\* http://www.mediawiki.org/wiki/Extension:Scribunto/Lua\_reference\_manual#Patterns
\* http://www.mediawiki.org/wiki/Extension:Scribunto/Lua\_reference\_manual#Ustring\_patterns

]]
function str.match( frame )
 local new\_args = str.\_getParameters( frame.args, {'s', 'pattern', 'start', 'match', 'plain', 'nomatch'} );
 local s = new\_args['s'] or '';
 local start = tonumber( new\_args['start'] ) or 1;
 local plain\_flag = str.\_getBoolean( new\_args['plain'] or false );
 local pattern = new\_args['pattern'] or '';
 local match\_index = math.floor( tonumber(new\_args['match']) or 1 );
 local nomatch = new\_args['nomatch'];

 if s == '' then
 return str.\_error( 'Target string is empty' );
 end
 if pattern == '' then
 return str.\_error( 'Pattern string is empty' );
 end
 if math.abs(start) < 1 or math.abs(start) > mw.ustring.len( s ) then
 return str.\_error( 'Requested start is out of range' );
 end
 if match\_index == 0 then
 return str.\_error( 'Match index is out of range' );
 end
 if plain\_flag then
 pattern = str.\_escapePattern( pattern );
 end

 local result
 if match\_index == 1 then
 -- Find first match is simple case
 result = mw.ustring.match( s, pattern, start )
 else
 if start > 1 then
 s = mw.ustring.sub( s, start );
 end

 local iterator = mw.ustring.gmatch(s, pattern);
 if match\_index > 0 then
 -- Forward search
 for w in iterator do
 match\_index = match\_index - 1;
 if match\_index == 0 then
 result = w;
 break;
 end
 end
 else
 -- Reverse search
 local result\_table = {};
 local count = 1;
 for w in iterator do
 result\_table[count] = w;
 count = count + 1;
 end

 result = result\_table[ count + match\_index ];
 end
 end

 if result == nil then
 if nomatch == nil then
 return str.\_error( 'Match not found' );
 else
 return nomatch;
 end
 else
 return result;
 end
end

--[[
pos

This function returns a single character from the target string at position pos.

Usage:
{{#invoke:String|pos|target\_string|index\_value}}
OR
{{#invoke:String|pos|target=target\_string|pos=index\_value}}

Parameters
 target: The string to search
 pos: The index for the character to return

If invoked using named parameters, Mediawiki will automatically remove any leading or
trailing whitespace from the target string. In some circumstances this is desirable, in
other cases one may want to preserve the whitespace.

The first character has an index value of 1.

If one requests a negative value, this function will select a character by counting backwards
from the end of the string. In other words pos = -1 is the same as asking for the last character.

A requested value of zero, or a value greater than the length of the string returns an error.
]]
function str.pos( frame )
 local new\_args = str.\_getParameters( frame.args, {'target', 'pos'} );
 local target\_str = new\_args['target'] or '';
 local pos = tonumber( new\_args['pos'] ) or 0;

 if pos == 0 or math.abs(pos) > mw.ustring.len( target\_str ) then
 return str.\_error( 'String index out of range' );
 end

 return mw.ustring.sub( target\_str, pos, pos );
end

--[[
str\_find

This function duplicates the behavior of {{str\_find}}, including all of its quirks.
This is provided in order to support existing templates, but is NOT RECOMMENDED for
new code and templates. New code is recommended to use the "find" function instead.

Returns the first index in "source" that is a match to "target". Indexing is 1-based,
and the function returns -1 if the "target" string is not present in "source".

Important Note: If the "target" string is empty / missing, this function returns a
value of "1", which is generally unexpected behavior, and must be accounted for
separatetly.
]]
function str.str\_find( frame )
 local new\_args = str.\_getParameters( frame.args, {'source', 'target'} );
 local source\_str = new\_args['source'] or '';
 local target\_str = new\_args['target'] or '';

 if target\_str == '' then
 return 1;
 end

 local start = mw.ustring.find( source\_str, target\_str, 1, true )
 if start == nil then
 start = -1
 end

 return start
end

--[[
find

This function allows one to search for a target string or pattern within another
string.

Usage:
OR

Parameters
 source: The string to search
 target: The string or pattern to find within source
 start: The index within the source string to start the search, defaults to 1
 plain: Boolean flag indicating that target should be understood as plain
 text and not as a Lua style regular expression, defaults to true

If invoked using named parameters, Mediawiki will automatically remove any leading or
trailing whitespace from the parameter. In some circumstances this is desirable, in
other cases one may want to preserve the whitespace.

This function returns the first index >= "start" where "target" can be found
within "source". Indices are 1-based. If "target" is not found, then this
function returns 0. If either "source" or "target" are missing / empty, this
function also returns 0.

This function should be safe for UTF-8 strings.
]]
function str.find( frame )
 local new\_args = str.\_getParameters( frame.args, {'source', 'target', 'start', 'plain' } );
 local source\_str = new\_args['source'] or '';
 local pattern = new\_args['target'] or '';
 local start\_pos = tonumber(new\_args['start']) or 1;
 local plain = new\_args['plain'] or true;

 if source\_str == '' or pattern == '' then
 return 0;
 end

 plain = str.\_getBoolean( plain );

 local start = mw.ustring.find( source\_str, pattern, start\_pos, plain )
 if start == nil then
 start = 0
 end

 return start
end

--[[
replace

This function allows one to replace a target string or pattern within another
string.

Usage:
OR
 count=replacement\_count|plain=plain\_flag}}

Parameters
 source: The string to search
 pattern: The string or pattern to find within source
 replace: The replacement text
 count: The number of occurences to replace, defaults to all.
 plain: Boolean flag indicating that pattern should be understood as plain
 text and not as a Lua style regular expression, defaults to true
]]
function str.replace( frame )
 local new\_args = str.\_getParameters( frame.args, {'source', 'pattern', 'replace', 'count', 'plain' } );
 local source\_str = new\_args['source'] or '';
 local pattern = new\_args['pattern'] or '';
 local replace = new\_args['replace'] or '';
 local count = tonumber( new\_args['count'] );
 local plain = new\_args['plain'] or true;

 if source\_str == '' or pattern == '' then
 return source\_str;
 end
 plain = str.\_getBoolean( plain );

 if plain then
 pattern = str.\_escapePattern( pattern );
 replace = mw.ustring.gsub( replace, "%%", "%%%%" ); --Only need to escape replacement sequences.
 end

 local result;

 if count ~= nil then
 result = mw.ustring.gsub( source\_str, pattern, replace, count );
 else
 result = mw.ustring.gsub( source\_str, pattern, replace );
 end

 return result;
end

--[[
 simple function to pipe string.rep to templates.
]]

function str.rep( frame )
 local repetitions = tonumber( frame.args[2] )
 if not repetitions then
 return str.\_error( 'function rep expects a number as second parameter, received "' .. ( frame.args[2] or '' ) .. '"' )
 end
 return string.rep( frame.args[1] or '', repetitions )
end

--[[
Helper function that populates the argument list given that user may need to use a mix of
named and unnamed parameters. This is relevant because named parameters are not
identical to unnamed parameters due to string trimming, and when dealing with strings
we sometimes want to either preserve or remove that whitespace depending on the application.
]]
function str.\_getParameters( frame\_args, arg\_list )
 local new\_args = {};
 local index = 1;
 local value;

 for i,arg in ipairs( arg\_list ) do
 value = frame\_args[arg]
 if value == nil then
 value = frame\_args[index];
 index = index + 1;
 end
 new\_args[arg] = value;
 end

 return new\_args;
end

--[[
Helper function to handle error messages.
]]
function str.\_error( error\_str )
 local frame = mw.getCurrentFrame();
 local error\_category = frame.args.error\_category or 'Errors reported by Module String';
 local ignore\_errors = frame.args.ignore\_errors or false;
 local no\_category = frame.args.no\_category or false;

 if str.\_getBoolean(ignore\_errors) then
 return '';
 end

 local error\_str = '<strong class="error">String Module Error: ' .. error\_str .. '</strong>';
 if error\_category ~= '' and not str.\_getBoolean( no\_category ) then
 error\_str = '[[Category:' .. error\_category .. ']]' .. error\_str;
 end

 return error\_str;
end

--[[
Helper Function to interpret boolean strings
]]
function str.\_getBoolean( boolean\_str )
 local boolean\_value;

 if type( boolean\_str ) == 'string' then
 boolean\_str = boolean\_str:lower();
 if boolean\_str == 'false' or boolean\_str == 'no' or boolean\_str == '0'
 or boolean\_str == '' then
 boolean\_value = false;
 else
 boolean\_value = true;
 end
 elseif type( boolean\_str ) == 'boolean' then
 boolean\_value = boolean\_str;
 else
 error( 'No boolean value found' );
 end
 return boolean\_value
end

--[[
Helper function that escapes all pattern characters so that they will be treated
as plain text.
]]
function str.\_escapePattern( pattern\_str )
 return mw.ustring.gsub( pattern\_str, "([%(%)%.%%%+%-%\*%?%[%^%$%]])", "%%%1" );
end

return str
[[Category:Modules]]

```