#!/bin/perl

use Math::Trig;

# SVG Gosper curve generator by Blotwell
# Released under GFDL
# adapted from logo implementation https://de.wikipedia.org/wiki/Gosper-Kurve

BEGIN{ print <<"HEREDOC";
<?xml version="1.0" encoding="ISO-8859-1" standalone="no"?> <!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 20010904//EN"

   "http://www.w3.org/TR/2001/REC-SVG-20010904/DTD/svg10.dtd">
   <svg xmlns="http://www.w3.org/2000/svg"
        xmlns:xlink="http://www.w3.org/1999/xlink" xml:space="preserve"
               width="320px" height="320px"
                        viewBox="0 0 6400 6400">

HEREDOC
}

my $x=500, $y=2500, $a=90; printf "<polyline points=\"%i,%i,",$x,$y; sub p {printf "%i,%i,",$x,$y;} sub fd {my $n=shift; $x+=$n*cos(deg2rad($a)); $y-=$n*sin(deg2rad($a)); p();} sub tl {$a+=shift;} sub rt {$a-=shift;} my $ln=100; rg(4);

sub gl {my $st=-1+shift; if ($st<0) {fd($ln);} else {tl(60); rg($st); rt(60); gl($st); gl($st); rt(120); gl($st); rt(60); rg($st); tl(120); rg($st); tl(60); gl($st);}}

sub rg {my $st=-1+shift; if ($st<0) {fd($ln);} else {rg($st); rt(60); gl($st); rt(120); gl($st); tl(60); rg($st); tl(120); rg($st); rg($st); tl(60); gl($st); rt(60);}}

END{print '" stroke="black" stroke-width="30" stroke-linejoin="round" fill-opacity="0" />',"\n</svg>\n";}