From c293af9b57a3eae2969d49f629b67bb3d88c1bf3 Mon Sep 17 00:00:00 2001 From: Peter Jaszkowiak Date: Wed, 19 Feb 2025 21:06:48 -0700 Subject: [PATCH] add `IntoBounds::intersect` and `RangeBounds::is_empty` --- library/core/src/ops/range.rs | 140 +++++++++++++++++- .../method-suggestion-no-duplication.stderr | 3 +- 2 files changed, 137 insertions(+), 6 deletions(-) diff --git a/library/core/src/ops/range.rs b/library/core/src/ops/range.rs index 5580faefacc0..e0c442e52921 100644 --- a/library/core/src/ops/range.rs +++ b/library/core/src/ops/range.rs @@ -771,13 +771,11 @@ pub trait RangeBounds { /// # Examples /// /// ``` - /// # fn main() { /// use std::ops::Bound::*; /// use std::ops::RangeBounds; /// /// assert_eq!((..10).start_bound(), Unbounded); /// assert_eq!((3..10).start_bound(), Included(&3)); - /// # } /// ``` #[stable(feature = "collections_range", since = "1.28.0")] fn start_bound(&self) -> Bound<&T>; @@ -789,13 +787,11 @@ pub trait RangeBounds { /// # Examples /// /// ``` - /// # fn main() { /// use std::ops::Bound::*; /// use std::ops::RangeBounds; /// /// assert_eq!((3..).end_bound(), Unbounded); /// assert_eq!((3..10).end_bound(), Excluded(&10)); - /// # } /// ``` #[stable(feature = "collections_range", since = "1.28.0")] fn end_bound(&self) -> Bound<&T>; @@ -829,6 +825,71 @@ pub trait RangeBounds { Unbounded => true, }) } + + /// Returns `true` if the range contains no items. + /// One-sided ranges (`RangeFrom`, etc) always return `true`. + /// + /// # Examples + /// + /// ``` + /// #![feature(range_bounds_is_empty)] + /// use std::ops::RangeBounds; + /// + /// assert!(!(3..).is_empty()); + /// assert!(!(..2).is_empty()); + /// assert!(!RangeBounds::is_empty(&(3..5))); + /// assert!( RangeBounds::is_empty(&(3..3))); + /// assert!( RangeBounds::is_empty(&(3..2))); + /// ``` + /// + /// The range is empty if either side is incomparable: + /// + /// ``` + /// #![feature(range_bounds_is_empty)] + /// use std::ops::RangeBounds; + /// + /// assert!(!RangeBounds::is_empty(&(3.0..5.0))); + /// assert!( RangeBounds::is_empty(&(3.0..f32::NAN))); + /// assert!( RangeBounds::is_empty(&(f32::NAN..5.0))); + /// ``` + /// + /// But never empty is either side is unbounded: + /// + /// ``` + /// #![feature(range_bounds_is_empty)] + /// use std::ops::RangeBounds; + /// + /// assert!(!(..0).is_empty()); + /// assert!(!(i32::MAX..).is_empty()); + /// assert!(!RangeBounds::::is_empty(&(..))); + /// ``` + /// + /// `(Excluded(a), Excluded(b))` is only empty if `a >= b`: + /// + /// ``` + /// #![feature(range_bounds_is_empty)] + /// use std::ops::Bound::*; + /// use std::ops::RangeBounds; + /// + /// assert!(!(Excluded(1), Excluded(3)).is_empty()); + /// assert!(!(Excluded(1), Excluded(2)).is_empty()); + /// assert!( (Excluded(1), Excluded(1)).is_empty()); + /// assert!( (Excluded(2), Excluded(1)).is_empty()); + /// assert!( (Excluded(3), Excluded(1)).is_empty()); + /// ``` + #[unstable(feature = "range_bounds_is_empty", issue = "137300")] + fn is_empty(&self) -> bool + where + T: PartialOrd, + { + !match (self.start_bound(), self.end_bound()) { + (Unbounded, _) | (_, Unbounded) => true, + (Included(start), Excluded(end)) + | (Excluded(start), Included(end)) + | (Excluded(start), Excluded(end)) => start < end, + (Included(start), Included(end)) => start <= end, + } + } } /// Used to convert a range into start and end bounds, consuming the @@ -845,7 +906,6 @@ pub trait IntoBounds: RangeBounds { /// /// ``` /// #![feature(range_into_bounds)] - /// /// use std::ops::Bound::*; /// use std::ops::IntoBounds; /// @@ -853,6 +913,76 @@ pub trait IntoBounds: RangeBounds { /// assert_eq!((..=7).into_bounds(), (Unbounded, Included(7))); /// ``` fn into_bounds(self) -> (Bound, Bound); + + /// Compute the intersection of `self` and `other`. + /// + /// # Examples + /// + /// ``` + /// #![feature(range_into_bounds)] + /// use std::ops::Bound::*; + /// use std::ops::IntoBounds; + /// + /// assert_eq!((3..).intersect(..5), (Included(3), Excluded(5))); + /// assert_eq!((-12..387).intersect(0..256), (Included(0), Excluded(256))); + /// assert_eq!((1..5).intersect(..), (Included(1), Excluded(5))); + /// assert_eq!((1..=9).intersect(0..10), (Included(1), Included(9))); + /// assert_eq!((7..=13).intersect(8..13), (Included(8), Excluded(13))); + /// ``` + /// + /// Combine with `is_empty` to determine if two ranges overlap. + /// + /// ``` + /// #![feature(range_into_bounds)] + /// #![feature(range_bounds_is_empty)] + /// use std::ops::{RangeBounds, IntoBounds}; + /// + /// assert!(!(3..).intersect(..5).is_empty()); + /// assert!(!(-12..387).intersect(0..256).is_empty()); + /// assert!((1..5).intersect(6..).is_empty()); + /// ``` + fn intersect(self, other: R) -> (Bound, Bound) + where + Self: Sized, + T: Ord, + R: Sized + IntoBounds, + { + let (self_start, self_end) = IntoBounds::into_bounds(self); + let (other_start, other_end) = IntoBounds::into_bounds(other); + + let start = match (self_start, other_start) { + (Included(a), Included(b)) => Included(Ord::max(a, b)), + (Excluded(a), Excluded(b)) => Excluded(Ord::max(a, b)), + (Unbounded, Unbounded) => Unbounded, + + (x, Unbounded) | (Unbounded, x) => x, + + (Included(i), Excluded(e)) | (Excluded(e), Included(i)) => { + if i > e { + Included(i) + } else { + Excluded(e) + } + } + }; + let end = match (self_end, other_end) { + (Included(a), Included(b)) => Included(Ord::min(a, b)), + (Excluded(a), Excluded(b)) => Excluded(Ord::min(a, b)), + (Unbounded, Unbounded) => Unbounded, + + (x, Unbounded) | (Unbounded, x) => x, + + (Included(i), Excluded(e)) | (Excluded(e), Included(i)) => { + if i < e { + Included(i) + } else { + Excluded(e) + } + } + }; + + (start, end) + } } use self::Bound::{Excluded, Included, Unbounded}; diff --git a/tests/ui/impl-trait/method-suggestion-no-duplication.stderr b/tests/ui/impl-trait/method-suggestion-no-duplication.stderr index c401269da83c..6bc57f89467d 100644 --- a/tests/ui/impl-trait/method-suggestion-no-duplication.stderr +++ b/tests/ui/impl-trait/method-suggestion-no-duplication.stderr @@ -8,8 +8,9 @@ LL | foo(|s| s.is_empty()); | ^^^^^^^^ method not found in `Foo` | = help: items from traits can only be used if the trait is implemented and in scope - = note: the following trait defines an item `is_empty`, perhaps you need to implement it: + = note: the following traits define an item `is_empty`, perhaps you need to implement one of them: candidate #1: `ExactSizeIterator` + candidate #2: `RangeBounds` error: aborting due to 1 previous error