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Specialize "loops of next" #818

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merged 8 commits into from
Dec 14, 2023
Merged

Specialize "loops of next" #818

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4fc8734
`FilterOk::next`: use `find`
Philippe-Cholet Nov 20, 2023
0969d4c
`FilterMapOk::next`: use `find_map`
Philippe-Cholet Nov 20, 2023
7df930e
`UniqueBy::next`: use `find`
Philippe-Cholet Nov 20, 2023
64952fc
`UniqueBy::next_back`: use `rfind`
Philippe-Cholet Nov 20, 2023
a1ec8fb
`Unique::next`: use `find_map`
Philippe-Cholet Nov 20, 2023
2c5a8a8
`Unique::next_back`: use `rev().find_map`
Philippe-Cholet Nov 20, 2023
e286c1b
`partition`: use `rfind`
Philippe-Cholet Nov 20, 2023
b87cc6a
Bench `partition`
Philippe-Cholet Dec 13, 2023
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9 changes: 5 additions & 4 deletions src/unique_impl.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -133,14 +133,15 @@ where
I::Item: Eq + Hash + Clone,
{
fn next_back(&mut self) -> Option<Self::Item> {
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.

if let Entry::Vacant(entry) = used.entry(v) {
let elt = entry.key().clone();
entry.insert(());
return Some(elt);
}
}
None
None
})
}
}

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