Sierpinski square curve: Difference between revisions

Uses Image Magick and

the PPM class from http://rosettacode.org/wiki/Bitmap/Bresenham%27s_line_algorithm#zkl

<lang zkl>sierpinskiSquareCurve(4) : turtle(_);

fcn sierpinskiSquareCurve(n){ // Lindenmayer system --> Data of As

var [const] A="AF-F+F-AF+F+AF-F+F-A", B=""; // Production rules

var [const] Axiom="F+AF+F+AF";

buf1,buf2 := Data(Void,Axiom).howza(3), Data().howza(3); // characters

do(n){

buf1.pump(buf2.clear(),fcn(c){ if(c=="A") A else if(c=="B") B else c });

t:=buf1; buf1=buf2; buf2=t; // swap buffers

}

buf1 // n=4 --> 3,239 characters

}

fcn turtle(curve){ // a "square" turtle, directions are +-90*

const D=10;

ds,dir := T( T(D,0), T(0,-D), T(-D,0), T(0,D) ), 2; // turtle offsets

dx,dy := ds[dir];

img,color := PPM(650,650), 0x00ff00; // green on black

x,y := img.w/2, 10;

curve.replace("A","").replace("B",""); // A & B are no-op during drawing

foreach c in (curve){

switch(c){

case("F"){ img.line(x,y, (x+=dx),(y+=dy), color) } // draw forward

case("+"){ dir=(dir+1)%4; dx,dy = ds[dir] } // turn right 90*

case("-"){ dir=(dir-1)%4; dx,dy = ds[dir] } // turn left 90*

}

}

img.writeJPGFile("sierpinskiSquareCurve.zkl.jpg");

}</lang>

{{out}}

Offsite image at [http://www.zenkinetic.com/Images/RosettaCode/sierpinskiSquareCurve.zkl.jpg Sierpinski square curve of order 4]