use super::size_hint;
#[derive(Clone, Debug)]
#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
pub struct Zip<T> {
t: T,
}
pub fn multizip<T, U>(t: U) -> Zip<T>
where Zip<T>: From<U>,
Zip<T>: Iterator,
{
Zip::from(t)
}
macro_rules! impl_zip_iter {
($($B:ident),*) => (
#[allow(non_snake_case)]
impl<$($B: IntoIterator),*> From<($($B,)*)> for Zip<($($B::IntoIter,)*)> {
fn from(t: ($($B,)*)) -> Self {
let ($($B,)*) = t;
Zip { t: ($($B.into_iter(),)*) }
}
}
#[allow(non_snake_case)]
#[allow(unused_assignments)]
impl<$($B),*> Iterator for Zip<($($B,)*)>
where
$(
$B: Iterator,
)*
{
type Item = ($($B::Item,)*);
fn next(&mut self) -> Option<Self::Item>
{
let ($(ref mut $B,)*) = self.t;
$(
let $B = match $B.next() {
None => return None,
Some(elt) => elt
};
)*
Some(($($B,)*))
}
fn size_hint(&self) -> (usize, Option<usize>)
{
let sh = (::std::usize::MAX, None);
let ($(ref $B,)*) = self.t;
$(
let sh = size_hint::min($B.size_hint(), sh);
)*
sh
}
}
#[allow(non_snake_case)]
impl<$($B),*> ExactSizeIterator for Zip<($($B,)*)> where
$(
$B: ExactSizeIterator,
)*
{ }
#[allow(non_snake_case)]
impl<$($B),*> DoubleEndedIterator for Zip<($($B,)*)> where
$(
$B: DoubleEndedIterator + ExactSizeIterator,
)*
{
#[inline]
fn next_back(&mut self) -> Option<Self::Item> {
let ($(ref mut $B,)*) = self.t;
let size = *[$( $B.len(), )*].iter().min().unwrap();
$(
if $B.len() != size {
for _ in 0..$B.len() - size { $B.next_back(); }
}
)*
match ($($B.next_back(),)*) {
($(Some($B),)*) => Some(($($B,)*)),
_ => None,
}
}
}
);
}
impl_zip_iter!(A);
impl_zip_iter!(A, B);
impl_zip_iter!(A, B, C);
impl_zip_iter!(A, B, C, D);
impl_zip_iter!(A, B, C, D, E);
impl_zip_iter!(A, B, C, D, E, F);
impl_zip_iter!(A, B, C, D, E, F, G);
impl_zip_iter!(A, B, C, D, E, F, G, H);
impl_zip_iter!(A, B, C, D, E, F, G, H, I);
impl_zip_iter!(A, B, C, D, E, F, G, H, I, J);
impl_zip_iter!(A, B, C, D, E, F, G, H, I, J, K);
impl_zip_iter!(A, B, C, D, E, F, G, H, I, J, K, L);