Fixes nan value for powc of zero #116
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Is there anything I can still do to get this merged? |
src/lib.rs
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| @@ -1908,6 +1897,15 @@ pub(crate) mod test { | |||
| Complex::new(1.65826, -0.33502), | |||
| 1e-5 | |||
| )); | |||
| let z = Complex::new(0.0, 0.0); | |||
| assert!(close(z.powc(b), z)); | |||
| assert!(z.powc(Complex64::new(0., 0.)).is_nan()); | |||
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I think this result should be one -- in fact the standard f64::powf(x, 0.0) == 1.0 for any base, even NaN! I'm going to fix both powf and powc here...
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That's not mathematically correct though, 0^0 is indeterminate.
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See the prior discussions in rust-num/num-traits#78 and rust-num/num-traits#79. It's a pragmatic choice, especially to be consistent with std.
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That wikipedia article also says:
Another example is the expression 0^0. Whether this expression is left undefined, or is defined to equal 1, depends on the field of application and may vary between authors. For more, see the article Zero to the power of zero.
This is consistent with the standard library powf -- even for NaN!
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Let me know what you think of that additional change for 0 exponents. I'll tweak the release date when we're ready. |
I think it makes sense. So I'm fine with it. |
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bors r+ |
116: Fixes nan value for powc of zero r=cuviper a=domna Fixes #114 `@cuviper` I just added a check for zero here as I suggested in #114. Co-authored-by: domna <florian.dobener@physik.hu-berlin.de> Co-authored-by: Florian Dobener <github@schroedingerscat.org> Co-authored-by: Josh Stone <cuviper@gmail.com>
RELEASES.md
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| # Release 0.4.4 (2023-08-13) | |||
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| - [Fixes nan value for `powc` of zero][116] | |||
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| - [Fixes nan value for `powc` of zero][116] | |
| - [Fixes NaN value for `powc` of zero][116] |
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bors r- |
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Canceled. |
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bors r+ |
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Fixes #114
@cuviper I just added a check for zero here as I suggested in #114.