Specialize "loops of next"#818
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Philippe-Cholet merged 8 commits intorust-itertools:masterfrom Dec 14, 2023
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And then no need for a named loop anymore.
phimuemue
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Dec 13, 2023
| while let Some(v) = self.iter.iter.next_back() { | ||
| if let Entry::Vacant(entry) = self.iter.used.entry(v) { | ||
| let UniqueBy { iter, used, .. } = &mut self.iter; | ||
| iter.rev().find_map(|v| { |
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Off-topic: Is it strange that there's rfind, but no rfind_map?
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It's not off-topic to me. I was wondering the same question while writing this.
Maybe there is no large performance gain to expect compare to .rev().method(). I searched a bit but did not find anything.
More generally, DoubleEndedIterator does not have a lot of methods.
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There are some cases where
next/next_backis repeatedly called in a loop, where a specialized method would do the same job, except it might be faster if the iterator they adapt has some specialized faster method.It was the case in #816.
Those benchmarks are not that impressive, they are based on slices that roughly reimplement the while loop themselves. But if the iterator they adapt have a specialized
try_[r]foldon whichfind/find_map/rfindusually rely, then it should be faster.The code is shorter in multiple cases and I believe clearer.
The
partitionfunction did not have any benchmark, there is now one and there are no difference, both 330µs.