Require std::iter::Sum for Float

[dbrgn]

Would it be possible to require std::iter::Sum for Float or maybe for Num?

Right now I cannot .sum() an iterator over T: Float.

[cuviper]

It would be a breaking change to add that requirement to existing traits.

You could use T: Float + Sum, or make your own meta-trait:

trait MyFloat: Float + Sum {}
impl<T: Float + Sum> MyFloat for T {}