Generics and conversions

help
1

Below I will describe the problem. Question is, exists there a way to solve it (or how to do it).

I would like to have the Point type for i32 or f32 coordinates:

struct Point<T> {
   x: T,
   y: T,
};

where T is i32 or f32.

And now i would like to have something like this:

From <Point<T>> for Point<U> {       // Point<i32> -> Point<f32>
   ...
}

and

From <Point<U>> for Point<T> {.      // Point<f32> -> Point<i32>
   ...
}

Is there a way to solve it (or how to do it)?

piotrpsz

2

if you know you want only i32 and f32, you should just write them both.
note that
impl<T,U> From <Point<T>> for Point<U> and impl<T,U> From <Point<U>> for Point<T> are the exact same thing.

impl From <Point<i32>> for Point<f32>  {
   // TODO 
}


impl From <Point<f32>> for Point<i32>  {
   // TODO 
}
3

I would also consider restricting the types, if necessary:

trait Coordinate {}
impl Coordinate for i32 {}
impl Coordinate for f32 {}

struct Point<T: Coordinate> {
    x: T,
    y: T,
}

impl From<Point<f32>> for Point<i32> {
    fn from(value: Point<f32>) -> Self {
        todo!()
    }
}

impl From<Point<i32>> for Point<f32> {
    fn from(value: Point<i32>) -> Self {
        todo!()
    }
}
4

Bingo. This is exactly what I was looking for.
Thank you so much. You're 'marlez' greate :slight_smile:

piotrpsz

5

either

trait NumericConversion<T>{
 fn from(surce:T)->Self;
}
impl NumericConversion<i32> for f32{
.....
}
impl NumericConversion<f32> for i32{
.....
}
.... //other conversion you want to support

or

trait CoordType{
 fn from_f32(surce:f32)->Self;
 fn to_f32(self)->f32;
}
impl CoordType for f32{
.....
}
impl CoordType for i32{
.....
}
....//other types you want to support

then you use the traits for the conversion of the whole object

6

it is strongly advised not to put trait bounds on struct definition, as they will infect everything else and lead to a lot of noise.
bounds belong on impls