How do I use floating point number literals when using generic types?
floating-point, literals, rust, traits
Solution
Use the `FromPrimitive` trait:
use num_traits::{cast::FromPrimitive, float::Float};
fn scale_float<T: Float + FromPrimitive>(x: T) -> T {
x * T::from_f64(0.54).unwrap()
}
Or the standard library `From` / `Into` traits
fn scale_float<T>(x: T) -> T
where
T: Float,
f64: Into<T>
{
x * 0.54.into()
}
See also:
- How do I use number literals with the Integer trait from the num crate?
Problem
Regular float literals do not work: ``` extern crate num_traits; use num_traits::float::Float; fn scale_float<T: Float>(x: T) -> T { x * 0.54 } fn main() { let a: f64 = scale_float(1.23); } ``` ``` error[E0308]: mismatched types --> src/main.rs:6:9 | 6 | x * 0.54 | ^^^^ expected type parameter, found floating-point variable | = note: expected type `T` found type `{float}` ```