mandelbrot-naive.d

// 
import std.stdio;
import std.math;
import core.time;

class Complex {
    double x;
    double y;
    this(A)(A px, A py) {
        this.x = px;
        this.y = py;
    }
    unittest {
        auto complex = new Complex(2, 2);
        assert(complex.x == 2 && complex.y == 2);
    }
    auto abs() const {
        return fmax(this.x * this.x, this.y * this.y);
    }

    void add(T)(const T other) {
        this.x += other.x;
        this.y += other.y;
    }

    void mul(T)(const T other) {
        auto newX = this.x * other.x - this.y * other.y;
        auto newY = this.x * other.y + this.y * other.x;
        this.x = newX;
        this.y = newY;
    }
}
unittest {
    auto c = new Complex(5, 3);
    c.mul(new Complex(4, 2));
    assert(c.x == 14 && c.y == 22);
}
unittest {
    auto org = new Complex(0, 0);
    org.add(new Complex(3, 3));
    assert(org.x == 3 && org.y == 3);
}

auto iterate_mandelbrot(const Complex c, const int maxIters) {
    auto z = new Complex(0, 0);
    for (int i = 0; i < maxIters; i++) {
        if (z.abs() >= 2.0) {
            return i;
        }
        z.mul(z);
        z.add(c);
    }
    return maxIters;
}

const x0 = -2.5, x1 = 1, y0 = -1, y1 = 1;
const cols = 72, rows = 24;
const maxIters = 1000000;

void main() {
        auto now = MonoTime.currTime;
    for (double row = 0; row < rows; row++) {
        const y = (row / rows) * (y1 - y0) + y0;
        char[] str;
        for (double col = 0; col < cols; col++) {
            // double is needed here because otherwise "/" does integer division
            const x = (col / cols) * (x1 - x0) + x0;
            auto c = new Complex(x, y);
            auto iters = iterate_mandelbrot(c, maxIters);
            if (iters == 0) {
                str ~= '.';
            } else if (iters == 1) {
                str ~= '%';
            } else if (iters == 2) {
                str ~= '@';
            } else if (iters == maxIters) {
                str ~= ' ';
            } else {
                str ~= '#';
            }
        }
        str.writeln;
    }
    writeln(MonoTime.currTime - now);
}