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Remove genericity in StepBy::size_hint

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This commit is contained in:
Josh Stone 2019-07-11 16:03:21 -07:00
parent d940ddf8f5
commit b1fd3d024d
1 changed files with 15 additions and 5 deletions
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20
src/libcore/iter/adapters/mod.rs
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@ -448,14 +448,24 @@ impl<I> Iterator for StepBy<I> where I: Iterator {
#[inline]
fn size_hint(&self) -> (usize, Option<usize>) {
let inner_hint = self.iter.size_hint();
#[inline]
fn first_size(step: usize) -> impl Fn(usize) -> usize {
move |n| if n == 0 { 0 } else { 1 + (n - 1) / (step + 1) }
}
#[inline]
fn other_size(step: usize) -> impl Fn(usize) -> usize {
move |n| n / (step + 1)
}
let (low, high) = self.iter.size_hint();
if self.first_take {
let f = |n| if n == 0 { 0 } else { 1 + (n-1)/(self.step+1) };
(f(inner_hint.0), inner_hint.1.map(f))
let f = first_size(self.step);
(f(low), high.map(f))
} else {
let f = |n| n / (self.step+1);
(f(inner_hint.0), inner_hint.1.map(f))
let f = other_size(self.step);
(f(low), high.map(f))
}
}