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Add Complex::powi and assorted Pow impls #56

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merged 2 commits into from
Jun 6, 2019
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@cuviper cuviper commented Jun 4, 2019

Closes #18.

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cuviper commented Jun 6, 2019

The CI failure is legit, I neglected no-std support.

However, this is annoying, because adding blanket T: Float impls gated on a feature is technically a breaking change! Actually, that makes this PR a breaking change already, because someone could technically have this for their own custom F type already:

impl Pow<F> for Complex<F> {
    type Output = Complex<F>;

    fn pow(self, exp: F) -> Self::Output {
        // ...
    }
}

The blanket powc should be OK though (with std), because a third party can't write this:

impl Pow<Complex<F>> for Complex<F> {
    type Output = Complex<F>;

    fn pow(self, exp: Self) -> Self::Output {
        //...
    }
}
error[E0117]: only traits defined in the current crate can be implemented for arbitrary types
  --> src/lib.rs:35:1
   |
35 | impl Pow<Complex<F>> for Complex<F> {
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ impl doesn't use types inside crate
   |
   = note: the impl does not reference only types defined in this crate
   = note: define and implement a trait or new type instead

We also can't have a blanket impl `Pow<T>`, as it's a breaking change.
Instead, we add `Pow<f32>` and `Pow<f64>` where those are `Into<T>`.
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cuviper commented Jun 6, 2019

bors r+

bors bot added a commit that referenced this pull request Jun 6, 2019
56: Add Complex::powi and assorted Pow impls r=cuviper a=cuviper

Closes #18.

Co-authored-by: Josh Stone <cuviper@gmail.com>
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bors bot commented Jun 6, 2019

Build succeeded

@bors bors bot merged commit c3173f7 into rust-num:master Jun 6, 2019
@cuviper cuviper deleted the pow branch February 6, 2024 23:36
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Implement Pow for Complex
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