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;
}




VB: Const WIDTH = 243 
Dim n As Long
Dim points() As Single
Dim flag As Boolean












Private Sub lineto(x As Integer, y As Integer)
    If flag Then
        points(n, 1) = x
        points(n, 2) = y
    End If
    n = n + 1
End Sub
Private Sub Peano(ByVal x As Integer, ByVal y As Integer, ByVal lg As Integer, _
    ByVal i1 As Integer, ByVal i2 As Integer)
    If (lg = 1) Then
        Call lineto(x * 3, y * 3)
        Exit Sub
    End If
    lg = lg / 3
    Call Peano(x + (2 * i1 * lg), y + (2 * i1 * lg), lg, i1, i2)
    Call Peano(x + ((i1 - i2 + 1) * lg), y + ((i1 + i2) * lg), lg, i1, 1 - i2)
    Call Peano(x + lg, y + lg, lg, i1, 1 - i2)
    Call Peano(x + ((i1 + i2) * lg), y + ((i1 - i2 + 1) * lg), lg, 1 - i1, 1 - i2)
    Call Peano(x + (2 * i2 * lg), y + (2 * (1 - i2) * lg), lg, i1, i2)
    Call Peano(x + ((1 + i2 - i1) * lg), y + ((2 - i1 - i2) * lg), lg, i1, i2)
    Call Peano(x + (2 * (1 - i1) * lg), y + (2 * (1 - i1) * lg), lg, i1, i2)
    Call Peano(x + ((2 - i1 - i2) * lg), y + ((1 + i2 - i1) * lg), lg, 1 - i1, i2)
    Call Peano(x + (2 * (1 - i2) * lg), y + (2 * i2 * lg), lg, 1 - i1, i2)
End Sub
Sub main()
    n = 1: flag = False
    Call Peano(0, 0, WIDTH, 0, 0) 
    ReDim points(1 To n - 1, 1 To 2)
    n = 1: flag = True
    Call Peano(0, 0, WIDTH, 0, 0) 
    ActiveSheet.Shapes.AddPolyline points 
End Sub