Reword the caveats on array::map
#126100
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Reword the caveats on array::map
#126100
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Thanks to 107634 and some improvements in LLVM (particularly `dead_on_unwind`), the method actually optimizes reasonably well now. So focus the discussion on the fundamental ordering differences where the optimizer might never be able to fix it because of the different behaviour, and encouraging `Iterator::map` where an array wasn't actually ever needed.
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| /// That means that `arr.map(f).map(g)` is, in general, *not* equivalent to | ||
| /// `array.map(|x| g(f(x)))`, as the former calls `f` 4 times then `g` 4 times, | ||
| /// whereas the latter interleaves the calls (`fgfgfgfg`). |
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We shouldn't be talking about iterator evaluation order. E.g. next_chunk impls may evaluate like array.map and so any iterator method that uses chunking internally might also use that order.
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That wasn't meant to reject the update to map. I just meant that we shouldn't be referring to Iterator order since the latter depends on the implementation. No such concern applies to the array method since it's evaluated eagerly and there's no possibility of specializing that.
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Thanks to #107634 and some improvements in LLVM (particularly
dead_on_unwind), the method actually optimizes reasonably well now.So focus the discussion on the fundamental ordering differences where the optimizer might never be able to fix it because of the different behaviour, and keep encouraging
Iterator::mapwhere an array wasn't actually ever needed.