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Simplify Skip::nth and Skip::last implementations #68597

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Merged
merged 1 commit into from
Feb 18, 2020
Merged

Simplify Skip::nth and Skip::last implementations #68597

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20 changes: 7 additions & 13 deletions src/libcore/iter/adapters/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1801,17 +1801,15 @@ where
#[inline]
fn nth(&mut self, n: usize) -> Option<I::Item> {
// Can't just add n + self.n due to overflow.
if self.n == 0 {
self.iter.nth(n)
} else {
if self.n > 0 {
let to_skip = self.n;
self.n = 0;
// nth(n) skips n+1
if self.iter.nth(to_skip - 1).is_none() {
return None;
}
self.iter.nth(n)
}
self.iter.nth(n)
}

#[inline]
Expand All @@ -1827,17 +1825,13 @@ where

#[inline]
fn last(mut self) -> Option<I::Item> {
if self.n == 0 {
self.iter.last()
} else {
let next = self.next();
if next.is_some() {
// recurse. n should be 0.
self.last().or(next)
} else {
None
if self.n > 0 {
// nth(n) skips n+1
if self.iter.nth(self.n - 1).is_none() {
return None;
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I like using Try in cases like this, self.iter.nth(self.n - 1)?;

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That would work in this case but would make the code less symmetric with the other methods of Skip which is why I didn't use ? here.

}
}
self.iter.last()
}

#[inline]
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