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|
use super::size_hint;
/// See [`multizip`] for more information.
#[derive(Clone, Debug)]
#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
pub struct Zip<T> {
t: T,
}
/// An iterator that generalizes *.zip()* and allows running multiple iterators in lockstep.
///
/// The iterator `Zip<(I, J, ..., M)>` is formed from a tuple of iterators (or values that
/// implement [`IntoIterator`]) and yields elements
/// until any of the subiterators yields `None`.
///
/// The iterator element type is a tuple like like `(A, B, ..., E)` where `A` to `E` are the
/// element types of the subiterator.
///
/// **Note:** The result of this macro is a value of a named type (`Zip<(I, J,
/// ..)>` of each component iterator `I, J, ...`) if each component iterator is
/// nameable.
///
/// Prefer [`izip!()`] over `multizip` for the performance benefits of using the
/// standard library `.zip()`. Prefer `multizip` if a nameable type is needed.
///
/// ```
/// use itertools::multizip;
///
/// // iterate over three sequences side-by-side
/// let mut results = [0, 0, 0, 0];
/// let inputs = [3, 7, 9, 6];
///
/// for (r, index, input) in multizip((&mut results, 0..10, &inputs)) {
/// *r = index * 10 + input;
/// }
///
/// assert_eq!(results, [0 + 3, 10 + 7, 29, 36]);
/// ```
/// [`izip!()`]: crate::izip
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;
// NOTE: Just like iter::Zip, we check the iterators
// for None in order. We may finish unevenly (some
// iterators gave n + 1 elements, some only n).
$(
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);
|
