Task: Koch curve


C++: 
#include <fstream>
#include <iostream>
#include <vector>

constexpr double sqrt3_2 = 0.86602540378444; 

struct point {
    double x;
    double y;
};

std::vector<point> koch_next(const std::vector<point>& points) {
    size_t size = points.size();
    std::vector<point> output(4*(size - 1) + 1);
    double x0, y0, x1, y1;
    size_t j = 0;
    for (size_t i = 0; i + 1 < size; ++i) {
        x0 = points[i].x;
        y0 = points[i].y;
        x1 = points[i + 1].x;
        y1 = points[i + 1].y;
        double dy = y1 - y0;
        double dx = x1 - x0;
        output[j++] = {x0, y0};
        output[j++] = {x0 + dx/3, y0 + dy/3};
        output[j++] = {x0 + dx/2 - dy * sqrt3_2/3, y0 + dy/2 + dx * sqrt3_2/3};
        output[j++] = {x0 + 2 * dx/3, y0 + 2 * dy/3};
    }
    output[j] = {x1, y1};
    return output;
}

std::vector<point> koch_points(int size, int iterations) {
    double length = size * sqrt3_2 * 0.95;
    double x = (size - length)/2;
    double y = size/2 - length * sqrt3_2/3;
    std::vector<point> points{
        {x, y},
        {x + length/2, y + length * sqrt3_2},
        {x + length, y},
        {x, y}
    };
    for (int i = 0; i < iterations; ++i)
        points = koch_next(points);
    return points;
}

void koch_curve_svg(std::ostream& out, int size, int iterations) {
    out << "<svg xmlns='http:
        << size << "' height='" << size << "'>\n";
    out << "<rect width='100%' height='100%' fill='black'/>\n";
    out << "<path stroke-width='1' stroke='white' fill='none' d='";
    auto points(koch_points(size, iterations));
    for (size_t i = 0, n = points.size(); i < n; ++i)
        out << (i == 0 ? "M" : "L") << points[i].x << ',' << points[i].y << '\n';
    out << "z'/>\n</svg>\n";
}

int main() {
    std::ofstream out("koch_curve.svg");
    if (!out) {
        std::cerr << "Cannot open output file\n";
        return EXIT_FAILURE;
    }
    koch_curve_svg(out, 600, 5);
    return EXIT_SUCCESS;
}







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