Minimal Mandelbrot generator using CNL

mandelbrot.h

#include <cnl/fixed_point.h>
#include <array>

using namespace cnl;
using namespace std;

constexpr int mandelbrot(float f_x, float f_y, int const limit) {
    using scalar = fixed_point<int64_t, -28>;
    auto c_x = scalar{f_x};
    auto c_y = scalar{f_y};
    constexpr auto r = scalar{2};
    constexpr auto rr = r*r;

    auto x = c_x, y = c_y;
    for (auto i = 0; i != limit; ++ i) {
        auto xx = x*x;
        auto yy = y*y;
        if (xx+yy>rr) {
            return i;
        }
        y = scalar{2 * x * y} + c_y;
        x = scalar{xx - yy} + c_x;
    }
    return limit;
}

int main(int, char**) {
    for (auto y = -2.f; y <= 2; y += 1.f/8) {
        for (auto x = -2.f; x <= 2; x += 1.f/16) {
            auto i = mandelbrot(x, y, 95);
            putchar((i == 95 ? 0 : i) + ' ');
        }
        putchar('\n');
    }
    return 0;
}