Task: Peano curve





Java: import java.io.*;

public class PeanoCurve {
    public static void main(final String[] args) {
        try (Writer writer = new BufferedWriter(new FileWriter("peano_curve.svg"))) {
            PeanoCurve s = new PeanoCurve(writer);
            final int length = 8;
            s.currentAngle = 90;
            s.currentX = length;
            s.currentY = length;
            s.lineLength = length;
            s.begin(656);
            s.execute(rewrite(4));
            s.end();
        } catch (final Exception ex) {
            ex.printStackTrace();
        }
    }

    private PeanoCurve(final Writer writer) {
        this.writer = writer;
    }

    private void begin(final int size) throws IOException {
        write("<svg xmlns='http:
        write("<rect width='100%%' height='100%%' fill='white'/>\n");
        write("<path stroke-width='1' stroke='black' fill='none' d='");
    }

    private void end() throws IOException {
        write("'/>\n</svg>\n");
    }

    private void execute(final String s) throws IOException {
        write("M%g,%g\n", currentX, currentY);
        for (int i = 0, n = s.length(); i < n; ++i) {
            switch (s.charAt(i)) {
                case 'F':
                    line(lineLength);
                    break;
                case '+':
                    turn(ANGLE);
                    break;
                case '-':
                    turn(-ANGLE);
                    break;
            }
        }
    }

    private void line(final double length) throws IOException {
        final double theta = (Math.PI * currentAngle) / 180.0;
        currentX += length * Math.cos(theta);
        currentY += length * Math.sin(theta);
        write("L%g,%g\n", currentX, currentY);
    }

    private void turn(final int angle) {
        currentAngle = (currentAngle + angle) % 360;
    }

    private void write(final String format, final Object... args) throws IOException {
        writer.write(String.format(format, args));
    }

    private static String rewrite(final int order) {
        String s = "L";
        for (int i = 0; i < order; ++i) {
            final StringBuilder sb = new StringBuilder();
            for (int j = 0, n = s.length(); j < n; ++j) {
                final char ch = s.charAt(j);
                if (ch == 'L')
                    sb.append("LFRFL-F-RFLFR+F+LFRFL");
                else if (ch == 'R')
                    sb.append("RFLFR+F+LFRFL-F-RFLFR");
                else
                    sb.append(ch);
            }
            s = sb.toString();
        }
        return s;
    }

    private final Writer writer;
    private double lineLength;
    private double currentX;
    private double currentY;
    private int currentAngle;
    private static final int ANGLE = 90;
}



Python: import turtle as tt
import inspect

stack = [] 
def peano(iterations=1):
    global stack

    
    ivan = tt.Turtle(shape = "classic", visible = True)


    
    screen = tt.Screen()
    screen.title("Desenhin do Peano")
    screen.bgcolor("
    screen.delay(0) 
    screen.setup(width=0.95, height=0.9)

    
    walk = 1

    def screenlength(k):
        
        
        if k != 0:
            length = screenlength(k-1)
            return 2*length + 1
        else: return 0

    kkkj = screenlength(iterations)
    screen.setworldcoordinates(-1, -1, kkkj + 1, kkkj + 1)
    ivan.color("


    
    def step1(k):
        global stack
        stack.append(len(inspect.stack()))
        if k != 0:
            ivan.left(90)
            step2(k - 1)
            ivan.forward(walk)
            ivan.right(90)
            step1(k - 1)
            ivan.forward(walk)
            step1(k - 1)
            ivan.right(90)
            ivan.forward(walk)
            step2(k - 1)
            ivan.left(90)
    def step2(k):
        global stack
        stack.append(len(inspect.stack()))
        if k != 0:
            ivan.right(90)
            step1(k - 1)
            ivan.forward(walk)
            ivan.left(90)
            step2(k - 1)
            ivan.forward(walk)
            step2(k - 1)
            ivan.left(90)
            ivan.forward(walk)
            step1(k - 1)
            ivan.right(90)

    
    ivan.left(90)
    step2(iterations)

    tt.done()

if __name__ == "__main__":
    peano(4)
    import pylab as P 
    P.plot(stack)
    P.show()