diff --git a/library/core/src/iter/traits/collect.rs b/library/core/src/iter/traits/collect.rs index 7f87ead6feed6..aa91346851f9d 100644 --- a/library/core/src/iter/traits/collect.rs +++ b/library/core/src/iter/traits/collect.rs @@ -360,3 +360,61 @@ impl Extend<()> for () { } fn extend_one(&mut self, _item: ()) {} } + +#[stable(feature = "extend_for_tuple", since = "1.56.0")] +impl Extend<(A, B)> for (ExtendA, ExtendB) +where + ExtendA: Extend, + ExtendB: Extend, +{ + /// Allows to `extend` a tuple of collections that also implement `Extend`. + /// + /// See also: [`Iterator::unzip`] + /// + /// # Examples + /// ``` + /// let mut tuple = (vec![0], vec![1]); + /// tuple.extend(vec![(2, 3), (4, 5), (6, 7)]); + /// assert_eq!(tuple.0, vec![0, 2, 4, 6]); + /// assert_eq!(tuple.1, vec![1, 3, 5, 7]); + /// + /// // also allows for arbitrarily nested tuples + /// let mut nested_tuple = (vec![(1, -1)], vec![(2, -2)]); + /// nested_tuple.extend(vec![((3, -3), (4, -4)), ((5, -5), (6, -6))]); + /// + /// assert_eq!(nested_tuple.0, vec![(1, -1), (3, -3), (5, -5)]); + /// assert_eq!(nested_tuple.1, vec![(2, -2), (4, -4), (6, -6)]); + /// ``` + fn extend>(&mut self, into_iter: T) { + let (a, b) = self; + let iter = into_iter.into_iter(); + + fn extend<'a, A, B>( + a: &'a mut impl Extend, + b: &'a mut impl Extend, + ) -> impl FnMut((), (A, B)) + 'a { + move |(), (t, u)| { + a.extend_one(t); + b.extend_one(u); + } + } + + let (lower_bound, _) = iter.size_hint(); + if lower_bound > 0 { + a.extend_reserve(lower_bound); + b.extend_reserve(lower_bound); + } + + iter.fold((), extend(a, b)); + } + + fn extend_one(&mut self, item: (A, B)) { + self.0.extend_one(item.0); + self.1.extend_one(item.1); + } + + fn extend_reserve(&mut self, additional: usize) { + self.0.extend_reserve(additional); + self.1.extend_reserve(additional); + } +} diff --git a/library/core/src/iter/traits/iterator.rs b/library/core/src/iter/traits/iterator.rs index 6b24d33bebca3..524d8f857e2a5 100644 --- a/library/core/src/iter/traits/iterator.rs +++ b/library/core/src/iter/traits/iterator.rs @@ -2841,6 +2841,14 @@ pub trait Iterator { /// /// assert_eq!(left, [1, 3]); /// assert_eq!(right, [2, 4]); + /// + /// // you can also unzip multiple nested tuples at once + /// let a = [(1, (2, 3)), (4, (5, 6))]; + /// + /// let (x, (y, z)): (Vec<_>, (Vec<_>, Vec<_>)) = a.iter().cloned().unzip(); + /// assert_eq!(x, [1, 4]); + /// assert_eq!(y, [2, 5]); + /// assert_eq!(z, [3, 6]); /// ``` #[stable(feature = "rust1", since = "1.0.0")] fn unzip(self) -> (FromA, FromB) @@ -2849,28 +2857,9 @@ pub trait Iterator { FromB: Default + Extend, Self: Sized + Iterator, { - fn extend<'a, A, B>( - ts: &'a mut impl Extend, - us: &'a mut impl Extend, - ) -> impl FnMut((), (A, B)) + 'a { - move |(), (t, u)| { - ts.extend_one(t); - us.extend_one(u); - } - } - - let mut ts: FromA = Default::default(); - let mut us: FromB = Default::default(); - - let (lower_bound, _) = self.size_hint(); - if lower_bound > 0 { - ts.extend_reserve(lower_bound); - us.extend_reserve(lower_bound); - } - - self.fold((), extend(&mut ts, &mut us)); - - (ts, us) + let mut unzipped: (FromA, FromB) = Default::default(); + unzipped.extend(self); + unzipped } /// Creates an iterator which copies all of its elements.