Change neutral element of <fNN as iter::Sum> to neg_zero #129321
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The neutral element used to be positive zero, but +0 + -0 = +0 so -0 seems better indicated.
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rustbot has assigned @workingjubilee. Use |
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Does that mean that the empty list sums to -0.0? That sounds unexpected to me. |
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We could special case the empty iterator to give +0, but then we would loose a kind of "associativity", and |
Unexpected, perhaps, but swapping this sign shouldn't change the result of any expr that does @bors r+ |
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…iaskrgr Rollup of 6 pull requests Successful merges: - rust-lang#128727 (bump conflicting_repr_hints lint to be shown in dependencies) - rust-lang#129232 (Fix `thread::sleep` Duration-handling for ESP-IDF) - rust-lang#129321 (Change neutral element of <fNN as iter::Sum> to neg_zero) - rust-lang#129353 (llvm-wrapper: adapt for LLVM 20 API changes) - rust-lang#129363 (Force `LC_ALL=C` for all run-make tests) - rust-lang#129364 (safe transmute: gracefully bubble-up layout errors) r? `@ghost` `@rustbot` modify labels: rollup
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Rollup merge of rust-lang#129321 - krtab:float_sum, r=workingjubilee Change neutral element of <fNN as iter::Sum> to neg_zero The neutral element used to be positive zero, but +0 + -0 = +0 so -0 seems better indicated.
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This breaks portable-simd tests for cg_clif at least as portable-simd uses 0.0 as neutral element for reduce_sum(). |
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Oh, sure, need to mirror in the simd stuff. |
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This causes unintended side effects on presentation layer applications like using Tera templates, for example. |
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…=workingjubilee Document `Sum::sum` returns additive identities for `[]` Because the neutral element of `<fNN as iter::Sum>` was changed to `neg_zero`, the documentation needed to be updated, as it was reporting inadequate information about what should be expected from the return. Relevant Commit: rust-lang@4908188 Relevant Pull Request: rust-lang#129321 --- The referenced commit causes unintended side effects on presentation layer applications like using Tera templates, for example. I'm not sure what the motivation was behind the original change, but it seems like more discussion should be put into this issue and potentially have that change reverted.
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…=workingjubilee Document `Sum::sum` returns additive identities for `[]` Because the neutral element of `<fNN as iter::Sum>` was changed to `neg_zero`, the documentation needed to be updated, as it was reporting inadequate information about what should be expected from the return. Relevant Commit: rust-lang@4908188 Relevant Pull Request: rust-lang#129321 --- The referenced commit causes unintended side effects on presentation layer applications like using Tera templates, for example. I'm not sure what the motivation was behind the original change, but it seems like more discussion should be put into this issue and potentially have that change reverted.
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…=workingjubilee Document `Sum::sum` returns additive identities for `[]` Because the neutral element of `<fNN as iter::Sum>` was changed to `neg_zero`, the documentation needed to be updated, as it was reporting inadequate information about what should be expected from the return. Relevant Commit: rust-lang@4908188 Relevant Pull Request: rust-lang#129321 --- The referenced commit causes unintended side effects on presentation layer applications like using Tera templates, for example. I'm not sure what the motivation was behind the original change, but it seems like more discussion should be put into this issue and potentially have that change reverted.
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Rollup merge of rust-lang#136710 - JakenHerman:jaken/iterator-docs, r=workingjubilee Document `Sum::sum` returns additive identities for `[]` Because the neutral element of `<fNN as iter::Sum>` was changed to `neg_zero`, the documentation needed to be updated, as it was reporting inadequate information about what should be expected from the return. Relevant Commit: rust-lang@4908188 Relevant Pull Request: rust-lang#129321 --- The referenced commit causes unintended side effects on presentation layer applications like using Tera templates, for example. I'm not sure what the motivation was behind the original change, but it seems like more discussion should be put into this issue and potentially have that change reverted.
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…=workingjubilee Document `Sum::sum` returns additive identities for `[]` Because the neutral element of `<fNN as iter::Sum>` was changed to `neg_zero`, the documentation needed to be updated, as it was reporting inadequate information about what should be expected from the return. Relevant Commit: rust-lang@4908188 Relevant Pull Request: rust-lang#129321 --- The referenced commit causes unintended side effects on presentation layer applications like using Tera templates, for example. I'm not sure what the motivation was behind the original change, but it seems like more discussion should be put into this issue and potentially have that change reverted.
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The neutral element used to be positive zero, but +0 + -0 = +0 so -0 seems better indicated.