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use std::fmt;
use std::iter::ExactSizeIterator;
use std::iter::FusedIterator;
use std::iter::Iterator;
/// Iterator which may contain instance of
/// one of two specific implementations.
///
/// Note: For most methods providing custom
/// implementation may marginally
/// improve performance by avoiding
/// doing Left/Right match on every step
/// and doing it only once instead.
#[derive(Clone)]
pub enum EitherIter<L, R> {
Left(L),
Right(R),
}
impl<L, R> Iterator for EitherIter<L, R>
where
L: Iterator,
R: Iterator<Item = L::Item>,
{
type Item = L::Item;
fn next(&mut self) -> Option<Self::Item> {
match self {
EitherIter::Left(l) => l.next(),
EitherIter::Right(r) => r.next(),
}
}
fn size_hint(&self) -> (usize, Option<usize>) {
match self {
EitherIter::Left(l) => l.size_hint(),
EitherIter::Right(r) => r.size_hint(),
}
}
}
impl<L, R> ExactSizeIterator for EitherIter<L, R>
where
L: ExactSizeIterator,
R: ExactSizeIterator,
EitherIter<L, R>: Iterator,
{
fn len(&self) -> usize {
match self {
EitherIter::Left(l) => l.len(),
EitherIter::Right(r) => r.len(),
}
}
}
impl<L, R> FusedIterator for EitherIter<L, R>
where
L: FusedIterator,
R: FusedIterator,
EitherIter<L, R>: Iterator,
{
}
impl<L, R> fmt::Debug for EitherIter<L, R>
where
L: fmt::Debug,
R: fmt::Debug,
{
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
match self {
EitherIter::Left(l) => l.fmt(f),
EitherIter::Right(r) => r.fmt(f),
}
}
}
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