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Add Range[Inclusive]::is_empty

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During the RFC, it was discussed that figuring out whether a range is empty was subtle, and thus there should be a clear and obvious way to do it.  It can't just be ExactSizeIterator::is_empty (also unstable) because not all ranges are ExactSize -- not even Range<i32> or RangeInclusive<usize>.
This commit is contained in:
Scott McMurray 2018-02-09 01:47:18 -08:00
parent afa8acce25
commit 4f8049a2b0
5 changed files with 62 additions and 5 deletions
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36
src/libcore/ops/range.rs
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@ -92,7 +92,6 @@ impl<Idx: fmt::Debug> fmt::Debug for Range<Idx> {
}
}
#[unstable(feature = "range_contains", reason = "recently added as per RFC", issue = "32311")]
impl<Idx: PartialOrd<Idx>> Range<Idx> {
/// Returns `true` if `item` is contained in the range.
///
@ -109,9 +108,26 @@ impl<Idx: PartialOrd<Idx>> Range<Idx> {
/// assert!(!(3..3).contains(3));
/// assert!(!(3..2).contains(3));
/// ```
#[unstable(feature = "range_contains", reason = "recently added as per RFC", issue = "32311")]
pub fn contains(&self, item: Idx) -> bool {
(self.start <= item) && (item < self.end)
}
/// Returns `true` if the range contains no items.
///
/// # Examples
///
/// ```
/// #![feature(range_is_empty)]
///
/// assert!(!(3..5).is_empty());
/// assert!( (3..3).is_empty());
/// assert!( (3..2).is_empty());
/// ```
#[unstable(feature = "range_is_empty", reason = "recently added", issue = "123456789")]
pub fn is_empty(&self) -> bool {
!(self.start < self.end)
}
}
/// A range only bounded inclusively below (`start..`).
@ -280,7 +296,6 @@ impl<Idx: fmt::Debug> fmt::Debug for RangeInclusive<Idx> {
}
}
#[unstable(feature = "range_contains", reason = "recently added as per RFC", issue = "32311")]
impl<Idx: PartialOrd<Idx>> RangeInclusive<Idx> {
/// Returns `true` if `item` is contained in the range.
///
@ -298,9 +313,26 @@ impl<Idx: PartialOrd<Idx>> RangeInclusive<Idx> {
/// assert!( (3..=3).contains(3));
/// assert!(!(3..=2).contains(3));
/// ```
#[unstable(feature = "range_contains", reason = "recently added as per RFC", issue = "32311")]
pub fn contains(&self, item: Idx) -> bool {
self.start <= item && item <= self.end
}
/// Returns `true` if the range contains no items.
///
/// # Examples
///
/// ```
/// #![feature(range_is_empty,inclusive_range_syntax)]
///
/// assert!(!(3..=5).is_empty());
/// assert!(!(3..=3).is_empty());
/// assert!( (3..=2).is_empty());
/// ```
#[unstable(feature = "range_is_empty", reason = "recently added", issue = "123456789")]
pub fn is_empty(&self) -> bool {
!(self.start <= self.end)
}
}
/// A range only bounded inclusively above (`..=end`).