f32 and f64 powf NaN handling should be documented
#90429
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Area: Documentation for any part of the project, including the compiler, standard library, and tools
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Area: Floating point numbers and arithmetic
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Category: This is a bug.
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f64 part for bug rust-lang#90429
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f128 part for bug rust-lang#90429
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Document powf and powi values that are always 1.0 fixes bug rust-lang#90429
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Document powf and powi values that are always 1.0 fixes bug rust-lang#90429
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…gross35 Document powf and powi values that are always 1.0 fixes bug rust-lang#90429
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Rollup merge of rust-lang#136012 - hkBst:patch-22, r=workingjubilee,tgross35 Document powf and powi values that are always 1.0 fixes bug rust-lang#90429
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…gross35 Document powf and powi values that are always 1.0 fixes bug rust-lang#90429
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The
f32andf64powfmethods follow the IEEE 754-2008 recommendations for NaN handling, but these are quite surprising. For example,f64::powf(1.0, f64::NAN)returns1.0, notf64::NAN. This behavior should be documented.The current docs don't mention NaN at all, which leads one to assume that any argument being NaN would produce a NaN result, like arithmetic operations. But these are not the standard behavior for
powf.This was mentioned in #60468, which links a playground illustrating the exceptions.
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