diff --git a/library/core/benches/iter.rs b/library/core/benches/iter.rs index 0abe20e4ca3..4b40485d207 100644 --- a/library/core/benches/iter.rs +++ b/library/core/benches/iter.rs @@ -363,6 +363,13 @@ fn bench_partial_cmp(b: &mut Bencher) { b.iter(|| (0..100000).map(black_box).partial_cmp((0..100000).map(black_box))) } +#[bench] +fn bench_chain_partial_cmp(b: &mut Bencher) { + b.iter(|| { + (0..50000).chain(50000..100000).map(black_box).partial_cmp((0..100000).map(black_box)) + }) +} + #[bench] fn bench_lt(b: &mut Bencher) { b.iter(|| (0..100000).map(black_box).lt((0..100000).map(black_box))) diff --git a/library/core/src/iter/traits/iterator.rs b/library/core/src/iter/traits/iterator.rs index b2d08f4b0f6..45be7bdd8db 100644 --- a/library/core/src/iter/traits/iterator.rs +++ b/library/core/src/iter/traits/iterator.rs @@ -3461,36 +3461,27 @@ fn cmp(self, other: I) -> Ordering /// assert_eq!(xs.iter().cmp_by(&ys, |&x, &y| (2 * x).cmp(&y)), Ordering::Greater); /// ``` #[unstable(feature = "iter_order_by", issue = "64295")] - fn cmp_by(mut self, other: I, mut cmp: F) -> Ordering + fn cmp_by(self, other: I, cmp: F) -> Ordering where Self: Sized, I: IntoIterator, F: FnMut(Self::Item, I::Item) -> Ordering, { - let mut other = other.into_iter(); - - loop { - let x = match self.next() { - None => { - if other.next().is_none() { - return Ordering::Equal; - } else { - return Ordering::Less; - } - } - Some(val) => val, - }; - - let y = match other.next() { - None => return Ordering::Greater, - Some(val) => val, - }; - - match cmp(x, y) { - Ordering::Equal => (), - non_eq => return non_eq, + #[inline] + fn compare(mut cmp: F) -> impl FnMut(X, Y) -> ControlFlow + where + F: FnMut(X, Y) -> Ordering, + { + move |x, y| match cmp(x, y) { + Ordering::Equal => ControlFlow::CONTINUE, + non_eq => ControlFlow::Break(non_eq), } } + + match iter_compare(self, other.into_iter(), compare(cmp)) { + ControlFlow::Continue(ord) => ord, + ControlFlow::Break(ord) => ord, + } } /// [Lexicographically](Ord#lexicographical-comparison) compares the elements of this [`Iterator`] with those @@ -3546,36 +3537,27 @@ fn partial_cmp(self, other: I) -> Option /// ); /// ``` #[unstable(feature = "iter_order_by", issue = "64295")] - fn partial_cmp_by(mut self, other: I, mut partial_cmp: F) -> Option + fn partial_cmp_by(self, other: I, partial_cmp: F) -> Option where Self: Sized, I: IntoIterator, F: FnMut(Self::Item, I::Item) -> Option, { - let mut other = other.into_iter(); - - loop { - let x = match self.next() { - None => { - if other.next().is_none() { - return Some(Ordering::Equal); - } else { - return Some(Ordering::Less); - } - } - Some(val) => val, - }; - - let y = match other.next() { - None => return Some(Ordering::Greater), - Some(val) => val, - }; - - match partial_cmp(x, y) { - Some(Ordering::Equal) => (), - non_eq => return non_eq, + #[inline] + fn compare(mut partial_cmp: F) -> impl FnMut(X, Y) -> ControlFlow> + where + F: FnMut(X, Y) -> Option, + { + move |x, y| match partial_cmp(x, y) { + Some(Ordering::Equal) => ControlFlow::CONTINUE, + non_eq => ControlFlow::Break(non_eq), } } + + match iter_compare(self, other.into_iter(), compare(partial_cmp)) { + ControlFlow::Continue(ord) => Some(ord), + ControlFlow::Break(ord) => ord, + } } /// Determines if the elements of this [`Iterator`] are equal to those of @@ -3613,29 +3595,26 @@ fn eq(self, other: I) -> bool /// assert!(xs.iter().eq_by(&ys, |&x, &y| x * x == y)); /// ``` #[unstable(feature = "iter_order_by", issue = "64295")] - fn eq_by(mut self, other: I, mut eq: F) -> bool + fn eq_by(self, other: I, eq: F) -> bool where Self: Sized, I: IntoIterator, F: FnMut(Self::Item, I::Item) -> bool, { - let mut other = other.into_iter(); - - loop { - let x = match self.next() { - None => return other.next().is_none(), - Some(val) => val, - }; - - let y = match other.next() { - None => return false, - Some(val) => val, - }; - - if !eq(x, y) { - return false; + #[inline] + fn compare(mut eq: F) -> impl FnMut(X, Y) -> ControlFlow<()> + where + F: FnMut(X, Y) -> bool, + { + move |x, y| { + if eq(x, y) { ControlFlow::CONTINUE } else { ControlFlow::BREAK } } } + + match iter_compare(self, other.into_iter(), compare(eq)) { + ControlFlow::Continue(ord) => ord == Ordering::Equal, + ControlFlow::Break(()) => false, + } } /// Determines if the elements of this [`Iterator`] are unequal to those of @@ -3860,6 +3839,46 @@ unsafe fn __iterator_get_unchecked(&mut self, _idx: usize) -> Self::Item } } +/// Compares two iterators element-wise using the given function. +/// +/// If `ControlFlow::CONTINUE` is returned from the function, the comparison moves on to the next +/// elements of both iterators. Returning `ControlFlow::Break(x)` short-circuits the iteration and +/// returns `ControlFlow::Break(x)`. If one of the iterators runs out of elements, +/// `ControlFlow::Continue(ord)` is returned where `ord` is the result of comparing the lengths of +/// the iterators. +/// +/// Isolates the logic shared by ['cmp_by'](Iterator::cmp_by), +/// ['partial_cmp_by'](Iterator::partial_cmp_by), and ['eq_by'](Iterator::eq_by). +#[inline] +fn iter_compare(mut a: A, mut b: B, f: F) -> ControlFlow +where + A: Iterator, + B: Iterator, + F: FnMut(A::Item, B::Item) -> ControlFlow, +{ + #[inline] + fn compare<'a, B, X, T>( + b: &'a mut B, + mut f: impl FnMut(X, B::Item) -> ControlFlow + 'a, + ) -> impl FnMut(X) -> ControlFlow> + 'a + where + B: Iterator, + { + move |x| match b.next() { + None => ControlFlow::Break(ControlFlow::Continue(Ordering::Greater)), + Some(y) => f(x, y).map_break(ControlFlow::Break), + } + } + + match a.try_for_each(compare(&mut b, f)) { + ControlFlow::Continue(()) => ControlFlow::Continue(match b.next() { + None => Ordering::Equal, + Some(_) => Ordering::Less, + }), + ControlFlow::Break(x) => x, + } +} + #[stable(feature = "rust1", since = "1.0.0")] impl Iterator for &mut I { type Item = I::Item;