Re-implement float min/max in rust #42430
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r? @aturon (rust_highfive has picked a reviewer for you, use r? to override) |
| // Since we do not support sNaN in Rust yet, we do not need to handle them. | ||
| // FIXME(nagisa): due to https://bugs.llvm.org/show_bug.cgi?id=33303 we canonicalize by | ||
| // multiplying by 1.0. Should switch to the `canonicalize` when it works. | ||
| (if self < other || other.is_nan() { self } else { other }) * 1.0 |
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self < other so self is that minimal one, seems reasonable.
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The other one is/was wrong. I’ll just write down some tests.
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Tidy is failing because this isn't mentioned in the book. |
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Aturon's on vacation this week, so let's try... |
src/libcore/num/mod.rs
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| #[unstable(feature = "core_float_min_max", issue="0")] | ||
| fn max(self, other: Self) -> Self; | ||
| /// Returns the minimum of the two numbers. | ||
| #[unstable(feature = "core_float_min_max", issue="0")] |
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Since these are stable in the standard library I think it's fine to go ahead and stabilize them in libcore itself, this is just moving the implementation down a layer where we could
| // Since we do not support sNaN in Rust yet, we do not need to handle them. | ||
| // FIXME(nagisa): due to https://bugs.llvm.org/show_bug.cgi?id=33303 we canonicalize by | ||
| // multiplying by 1.0. Should switch to the `canonicalize` when it works. | ||
| (if self < other || self.is_nan() { other } else { self }) * 1.0 |
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FWIW the musl implementation is quite different, it's not clear to me that these are the same?
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The only difference between the implementations is handling of the signed zero. IEEE 754 allows to ignore the signed-ness of zero here and, if 0.0 is compared to -0.0, to return either one.
Even the C99 standard does not mention signed zeroes in the annex referenced by musl. It quite literally paraphrases the IEEE 754 and provides an example implementation which matches (with small differences) the one provided here.
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@bors: r+ |
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📌 Commit ba6cf1d has been approved by |
Re-implement float min/max in rust This also adds the relevant implementations into libcore. See #42423
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☀️ Test successful - status-appveyor, status-travis |
This also adds the relevant implementations into libcore.
See #42423