bjoernager/rust
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Undo the Sized specialization from Iterator::nth

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This commit is contained in:
Scott McMurray 2017-11-18 03:45:51 -08:00
parent aabfed5e0c
commit cef45b3baf
1 changed files with 6 additions and 26 deletions
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32
src/libcore/iter/iterator.rs
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@ -253,8 +253,12 @@ pub trait Iterator {
/// ```
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
fn nth(&mut self, n: usize) -> Option<Self::Item> {
self.spec_nth(n)
fn nth(&mut self, mut n: usize) -> Option<Self::Item> {
for x in self {
if n == 0 { return Some(x) }
n -= 1;
}
None
}
/// Creates an iterator starting at the same point, but stepping by
@ -2381,27 +2385,3 @@ impl<'a, I: Iterator + ?Sized> Iterator for &'a mut I {
(**self).nth(n)
}
}
trait SpecIterator : Iterator {
fn spec_nth(&mut self, n: usize) -> Option<Self::Item>;
}
impl<I: Iterator + ?Sized> SpecIterator for I {
default fn spec_nth(&mut self, mut n: usize) -> Option<Self::Item> {
for x in self {
if n == 0 { return Some(x) }
n -= 1;
}
None
}
}
impl<I: Iterator + Sized> SpecIterator for I {
fn spec_nth(&mut self, n: usize) -> Option<Self::Item> {
self.try_fold(n, move |i, x| {
if i == 0 { LoopState::Break(x) }
else { LoopState::Continue(i - 1) }
}).break_value()
}
}