Hi all,
I am trying to impement a Vec3 type which will behave nicely when multiplying with float types. Using the num crate I have access to the Float bound trait. and have it working in some instances but not all. Sample snippets below.
// this compiles fine
impl <F: Float> ops::Mul<F> for Vec3
{
type Output = Vec3;
fn mul(self, _rhs: F) > Vec3 {
let val =_rhs.to_f64().unwrap();
Vec3(self.0 * val, self.2 * val, self.2 * val)
}
}
// This is the implementaiton that complains
impl <F: Float> ops::Mul<&Vec3> for F{
type Output = Vec3;
fn mul(self, rhs: &Vec3)>Self::Output{
let val = self.to_f64().unwrap();
Vec3(val * rhs.0, val * rhs.1, val * rhs.2)
}
}
// These are the working implemtnations I am trying to replace with the one above
// impl ops::Mul<&Vec3> for f64 {
// type Output = Vec3;
// fn mul(self, rhs: &Vec3) > Self::Output {
// Vec3(self * rhs.0, self * rhs.1, self * rhs.2)
// }
// }
// impl ops::Mul<&Vec3> for f32 {
// type Output = Vec3;
// fn mul(self, rhs: &Vec3) > Self::Output {
// let val = self as f64;
// Vec3(val * rhs.0, val * rhs.1, val * rhs.2)
// }
// }
The error listed is
error[E0210]: type parameter F
must be covered by another type when it appears before the first local type (Vec3
)
> src/lib.rs:109:7

109  impl <F: Float> ops::Mul<&Vec3> for F{
 ^ type parameter F
must be covered by another type when it appears before the first local type (Vec3
)

= note: implementing a foreign trait is only possible if at least one of the types for which it is implemented is local, and no uncovered type parameters appear before that first local type
= note: in this case, 'before' refers to the following order: impl<..> ForeignTrait<T1, ..., Tn> for T0
, where T0
is the first and Tn
is the last
Not clear how to resolve this, not clear what they mean that Type F must be 'covered' by another type...
Any suggestions?