Task: Koch curve








VB: option explicit


const pi180= 0.01745329251994329576923690768489 
const pi=3.1415926535897932384626433832795 
class turtle
   
   dim fso
   dim fn
   dim svg
   
   dim iang  
   dim ori   
   dim incr
   dim pdown
   dim clr
   dim x
   dim y

   public property let orient(n):ori = n*pi180 :end property
   public property let iangle(n):iang= n*pi180 :end property
   public sub pd() : pdown=true: end sub 
   public sub pu()  :pdown=FALSE :end sub 
   
   public sub rt(i)  
     ori=ori - i*iang:
     if ori<0 then ori = ori+pi*2
   end sub 
   public sub lt(i):  
     ori=(ori + i*iang) 
     if ori>(pi*2) then ori=ori-pi*2
   end sub
   
   public sub bw(l)
      x= x+ cos(ori+pi)*l*incr
      y= y+ sin(ori+pi)*l*incr
   end sub 
   
   public sub fw(l)
      dim x1,y1 
      x1=x + cos(ori)*l*incr
      y1=y + sin(ori)*l*incr
      if pdown then line x,y,x1,y1
      x=x1:y=y1
   end sub
   
   Private Sub Class_Initialize()  
      setlocale "us"  
      initsvg
      pdown=true
   end sub
   
   Private Sub Class_Terminate()   
      disply
   end sub
   
   private sub line (x,y,x1,y1)
      svg.WriteLine "<line x1=""" & x & """ y1= """& y & """ x2=""" & x1& """ y2=""" & y1 & """/>"
   end sub 

   private sub disply()
       dim shell
       svg.WriteLine "</svg></body></html>"
       svg.close
       Set shell = CreateObject("Shell.Application") 
       shell.ShellExecute fn,1,False
   end sub 

   private sub initsvg()
     dim scriptpath
     Set fso = CreateObject ("Scripting.Filesystemobject")
     ScriptPath= Left(WScript.ScriptFullName, InStrRev(WScript.ScriptFullName, "\"))
     fn=Scriptpath & "SIERP.HTML"
     Set svg = fso.CreateTextFile(fn,True)
     if SVG IS nothing then wscript.echo "Can
     svg.WriteLine "<!DOCTYPE html>" &vbcrlf & "<html>" &vbcrlf & "<head>"
     svg.writeline "<style>" & vbcrlf & "line {stroke:rgb(255,0,0);stroke-width:.5}" &vbcrlf &"</style>"
     svg.writeline "</head>"&vbcrlf & "<body>"
     svg.WriteLine "<svg xmlns=""http://www.w3.org/2000/svg"" width=""800"" height=""800"" viewBox=""0 0 800 800"">" 
   end sub 
end class

sub koch (n,le)
  if n=0 then x.fw le :exit sub
  koch n-1, le/3
  x.lt 1
  koch n-1, le/3
  x.rt 2
  koch n-1, le/3
  x.lt 1
  koch n-1, le/3
end sub

 dim x,i
set x=new turtle
x.iangle=60
x.orient=0
x.incr=3
x.x=100:x.y=300
for i=0 to 3
  koch 7,100
  x.rt 2
next  
set x=nothing  




Ada: with Ada.Command_Line;
with Ada.Numerics.Generic_Elementary_Functions;
with Ada.Text_IO;
with PDF_Out;

procedure Koch_Curve is

   package Real_Math is
     new Ada.Numerics.Generic_Elementary_Functions (PDF_Out.Real);
   use Real_Math, PDF_Out, Ada.Command_Line, Ada.Text_IO;

   subtype Angle_Deg  is Real;
   type    Level_Type is range 0 .. 7;

   Purple : constant Color_Type := (0.7, 0.0, 0.5);
   Length : constant Real       := 400.0;
   Corner : constant Point      := (90.0, 580.0);

   Level     : Level_Type;
   Current   : Point      := (0.0, 0.0);
   Direction : Angle_Deg  := Angle_Deg'(60.0);
   Doc       : PDF_Out_File;

   procedure Koch (Level : Level_Type; Length : Real) is
   begin
      if Level = 0 then
         Current := Current + Length * Point'(Sin (Direction, 360.0),
                                              Cos (Direction, 360.0));
         Doc.Line (Corner + Current);
      else
         Koch (Level - 1, Length / 3.0);  Direction := Direction -  60.0;
         Koch (Level - 1, Length / 3.0);  Direction := Direction + 120.0;
         Koch (Level - 1, Length / 3.0);  Direction := Direction -  60.0;
         Koch (Level - 1, Length / 3.0);
      end if;
   end Koch;

begin
   if Argument_Count /= 1 then
      Put_Line ("koch_curve <level>");
      Put_Line ("  <level>   0 .. 7");
      Put_Line ("open koch.pdf to view ouput");
      return;
   end if;
   Level := Level_Type'Value (Argument (1));

   Doc.Create ("koch.pdf");
   Doc.Page_Setup (A4_Portrait);
   Doc.Margins (Margins_Type'(Left   => Cm_2_5,
                              others => One_cm));
   Doc.Color (Purple);
   Doc.Move (Corner);
   for A in 1 .. 3 loop
      Koch (Level, Length);
      Direction := Direction + 120.0;
   end loop;
   Doc.Finish_Path (Close_Path => True,
                    Rendering  => Fill,
                    Rule       => Even_Odd);
   Doc.Close;
end Koch_Curve;