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macro_rules! impl_cons_iter(
($_A:ident, $_B:ident, ) => ();
($A:ident, $($B:ident,)*) => (
impl_cons_iter!($($B,)*);
#[allow(non_snake_case)]
impl<X, Iter, $($B),*> Iterator for ConsTuples<Iter, (($($B,)*), X)>
where Iter: Iterator<Item = (($($B,)*), X)>,
{
type Item = ($($B,)* X, );
fn next(&mut self) -> Option<Self::Item> {
self.iter.next().map(|(($($B,)*), x)| ($($B,)* x, ))
}
fn size_hint(&self) -> (usize, Option<usize>) {
self.iter.size_hint()
}
fn fold<Acc, Fold>(self, accum: Acc, mut f: Fold) -> Acc
where Fold: FnMut(Acc, Self::Item) -> Acc,
{
self.iter.fold(accum, move |acc, (($($B,)*), x)| f(acc, ($($B,)* x, )))
}
}
#[allow(non_snake_case)]
impl<X, Iter, $($B),*> DoubleEndedIterator for ConsTuples<Iter, (($($B,)*), X)>
where Iter: DoubleEndedIterator<Item = (($($B,)*), X)>,
{
fn next_back(&mut self) -> Option<Self::Item> {
self.iter.next().map(|(($($B,)*), x)| ($($B,)* x, ))
}
}
);
);
impl_cons_iter!(A, B, C, D, E, F, G, H,);
#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
#[derive(Debug)]
pub struct ConsTuples<I, J>
where I: Iterator<Item=J>,
{
iter: I,
}
impl<I, J> Clone for ConsTuples<I, J>
where I: Clone + Iterator<Item=J>,
{
clone_fields!(iter);
}
pub fn cons_tuples<I, J>(iterable: I) -> ConsTuples<I, J>
where I: Iterator<Item=J>
{
ConsTuples { iter: iterable.into_iter() }
}