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Updated documentation to note the pow(0, 0) case. #79

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merged 2 commits into from
Aug 7, 2018
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Updated documentation to note the pow(0, 0) case. #79

merged 2 commits into from
Aug 7, 2018

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meltinglava
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Ref #78

cuviper
cuviper reviewed Aug 6, 2018
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src/pow.rs Outdated
@@ -173,13 +173,16 @@ mod float_impls {

/// Raises a value to the power of exp, using exponentiation by squaring.
///
/// Note that `0⁰` (`pow(0, 0)`) returnes `1`. Mathematicly this is undefined.
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spelling: should be "mathematically"

src/pow.rs Outdated
@@ -208,6 +211,8 @@ pub fn pow<T: Clone + One + Mul<T, Output = T>>(mut base: T, mut exp: usize) ->

/// Raises a value to the power of exp, returning `None` if an overflow occurred.
///
/// Note that `0⁰` (`checked_pow(0, 0)`) returnes `Some(1)`. Mathematicly this is undefined.
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*mathematically

@cuviper cuviper mentioned this pull request Aug 6, 2018
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@hauleth
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hauleth commented Aug 6, 2018

Quoting prof Knuth:

On the other hand, Cauchy had good reason to consider 0^0 as an undefined limiting form, in the sense that the limiting value of f(x)^g(x) is not known a priori when f(x) and g(x) approach 0 independently. In this much stronger sense, the value of 0^0 is less defined than, say, the value of 0 + 0. Both Cauchy and Libri were right, but Libri and his defenders did not understand why truth was on their side.

https://arxiv.org/abs/math/9205211

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cuviper commented Aug 7, 2018

@hauleth It's not clear to me if you're quoting that in favor or against, or just representing the debate.

Anyway, commenting the existing behavior is harmless.

bors r+

bors bot added a commit that referenced this pull request Aug 7, 2018
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Merge #79
5985a8b 
79: Updated documentation to note the pow(0, 0) case. r=cuviper a=meltinglava

Ref #78 

Co-authored-by: Roald <meltinglava>
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bors bot commented Aug 7, 2018

Build succeeded

@bors bors bot merged commit 2b975ba into rust-num:master Aug 7, 2018
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hauleth commented Aug 8, 2018 •
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@cuviper my comment was in favour of current behaviour as I think it is more reasonable solution in case of computation. pow(0, 0) is "mathematically undefined" when we are working in area of mathematical analysis, and in such case num crate isn't that much helpful. We could quote this paper as a reasoning for current behaviour and why we think it is acceptable for us.

@meltinglava meltinglava deleted the doc_change branch August 10, 2018 08:30
@cuviper cuviper mentioned this pull request Sep 17, 2018
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@cuviper cuviper mentioned this pull request May 3, 2019
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@cuviper cuviper mentioned this pull request Aug 12, 2023
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