Unable to multiply complex matrix with complex scalar from the left

[martin-jw]

Hi there,

It is currently not possible to multiply a complex matrix with a complex scalar from the left, as illustrated here:

use nalgebra::{Complex, Matrix2};

fn main() {
    let mat = Matrix2::<Complex<f32>>::identity();
    let c = Complex::<f32>::new(1.0, -1.0);

    let product = mat * c; // This works
    let product = c * mat; // This does not compile
}

I suspect this is because Complex might be an external type. Is there a way to fix this currently or is it not possible? It is not a huge issue since you can always swap the multiplication order, but it is annoying.

[tpdickso]

I think historically this was the case but this might no longer be true, as it's now fine to write impl X<...> for Y as long as X contains one locally-defined type constraining it -- there is an impl for Mul<f32> for Vector2<f32> so I don't see why this wouldn't be possible. I can take a look.

[tpdickso]

#1339