Rust matrix multiplication example

mat4.rs

// Based on
// https://gist.githubusercontent.com/csherratt/7634597/raw/b05699f444ab552eb79a7f7c0e1c5ac235c5222c/mat4.rs
// from
// https://csherratt.github.io/csherratt/blog/2013/11/24/matrix-multiply-in-rust/

struct Mat4 {
    dat: [[f32; 4]; 4]
}

impl Mat4 {
    pub fn mult_m(a: Mat4, b: &Mat4) -> Mat4
    {
        let mut out = Mat4 {
            dat: [[0., 0., 0., 0.],
                  [0., 0., 0., 0.],
                  [0., 0., 0., 0.],
                  [0., 0., 0., 0.]]
        };

        for i in 0..4 {
            for j in 0..4 {
                for k in 0..4 {
                    out.dat[i][j] += a.dat[i][k] * b.dat[k][j];
                }
            }
        }

        out
    }

    pub fn print(self)
    {
        for i in 0..4 {
            for j in 0..4 {
                print!("{} ", self.dat[i][j]);
            }
            print!("\n");
        }
    }
}

fn main()
{
    let mut a = Mat4 {
        dat: [[1., 1., 1., 1.],
              [1., 1., 1., 1.],
              [1., 1., 1., 1.],
              [1., 1., 1., 1.]]
    };

    let b = Mat4 {
        dat: [[1., 0., 0., 0.],
              [0., 1., 0., 0.],
              [0., 0., 1., 0.],
              [0., 0., 0., 1.]]
    };

    for _ in 0..100_000 {
        a = Mat4::mult_m(a, &b);
    }

    a.print();
}