Generic square function

How do I write a generic square function that works for f32, f64, i32, isize, usize ?

Here's what I have so far:

pub fn sqr<T: std::ops::Mul>(x: T) -> T {
    x * x

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The trait result is generic too, so if you want to restrict this to the same type, use Mul<Output = T>. You'll also need Copy to use x twice, or else switch the constraints to multiply by reference.

where for<'a, 'b> &'a T: Mul<&'b T, Output = T>

Just add a T: Copy + Mul<Output = T> bound and that will cover all numeric types in std


Thanks! The Mul<Output = T> makes complete sense in hindsight but was not obvious at first.

You could also return T::Output instead of T. The issue is that the Mul op allows for returning a type that's different than Self (it also allows for multiplying two different types but that's obviously not an issue here).

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One common use of that with Mul is to return a type that is twice the width of the input arguments
(e.g., u32 * u32 -> u64).