Left multiplication for vector spaces

This code example fails:

```rust
fn foo>(a: V, b: V, c: f64) -> V {
a * c + c * b
}
```

with this error:

```
error[E0277]: the trait bound `f64: std::ops::Mul` is not satisfied
|
| a * c + c * b
| ^ no implementation for `f64 * V`
|
= help: the trait `std::ops::Mul` is not implemented for `f64`
= help: consider adding a `where f64: std::ops::Mul` bound
```
(omitted source location in my project for clarity)

Is there a reason, why this can't be made work? As multiplication on the field commutes anyway, the operator should generally be available in this way.