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Diffstat (limited to 'library/core/src/ops/range.rs')
| -rw-r--r-- | library/core/src/ops/range.rs | 991 |
1 files changed, 991 insertions, 0 deletions
diff --git a/library/core/src/ops/range.rs b/library/core/src/ops/range.rs new file mode 100644 index 000000000..a3b148473 --- /dev/null +++ b/library/core/src/ops/range.rs @@ -0,0 +1,991 @@ +use crate::fmt; +use crate::hash::Hash; + +/// An unbounded range (`..`). +/// +/// `RangeFull` is primarily used as a [slicing index], its shorthand is `..`. +/// It cannot serve as an [`Iterator`] because it doesn't have a starting point. +/// +/// # Examples +/// +/// The `..` syntax is a `RangeFull`: +/// +/// ``` +/// assert_eq!((..), std::ops::RangeFull); +/// ``` +/// +/// It does not have an [`IntoIterator`] implementation, so you can't use it in +/// a `for` loop directly. This won't compile: +/// +/// ```compile_fail,E0277 +/// for i in .. { +/// // ... +/// } +/// ``` +/// +/// Used as a [slicing index], `RangeFull` produces the full array as a slice. +/// +/// ``` +/// let arr = [0, 1, 2, 3, 4]; +/// assert_eq!(arr[ .. ], [0, 1, 2, 3, 4]); // This is the `RangeFull` +/// assert_eq!(arr[ .. 3], [0, 1, 2 ]); +/// assert_eq!(arr[ ..=3], [0, 1, 2, 3 ]); +/// assert_eq!(arr[1.. ], [ 1, 2, 3, 4]); +/// assert_eq!(arr[1.. 3], [ 1, 2 ]); +/// assert_eq!(arr[1..=3], [ 1, 2, 3 ]); +/// ``` +/// +/// [slicing index]: crate::slice::SliceIndex +#[lang = "RangeFull"] +#[doc(alias = "..")] +#[derive(Copy, Clone, Default, PartialEq, Eq, Hash)] +#[stable(feature = "rust1", since = "1.0.0")] +pub struct RangeFull; + +#[stable(feature = "rust1", since = "1.0.0")] +impl fmt::Debug for RangeFull { + fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result { + write!(fmt, "..") + } +} + +/// A (half-open) range bounded inclusively below and exclusively above +/// (`start..end`). +/// +/// The range `start..end` contains all values with `start <= x < end`. +/// It is empty if `start >= end`. +/// +/// # Examples +/// +/// The `start..end` syntax is a `Range`: +/// +/// ``` +/// assert_eq!((3..5), std::ops::Range { start: 3, end: 5 }); +/// assert_eq!(3 + 4 + 5, (3..6).sum()); +/// ``` +/// +/// ``` +/// let arr = [0, 1, 2, 3, 4]; +/// assert_eq!(arr[ .. ], [0, 1, 2, 3, 4]); +/// assert_eq!(arr[ .. 3], [0, 1, 2 ]); +/// assert_eq!(arr[ ..=3], [0, 1, 2, 3 ]); +/// assert_eq!(arr[1.. ], [ 1, 2, 3, 4]); +/// assert_eq!(arr[1.. 3], [ 1, 2 ]); // This is a `Range` +/// assert_eq!(arr[1..=3], [ 1, 2, 3 ]); +/// ``` +#[lang = "Range"] +#[doc(alias = "..")] +#[derive(Clone, Default, PartialEq, Eq, Hash)] // not Copy -- see #27186 +#[stable(feature = "rust1", since = "1.0.0")] +pub struct Range<Idx> { + /// The lower bound of the range (inclusive). + #[stable(feature = "rust1", since = "1.0.0")] + pub start: Idx, + /// The upper bound of the range (exclusive). + #[stable(feature = "rust1", since = "1.0.0")] + pub end: Idx, +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl<Idx: fmt::Debug> fmt::Debug for Range<Idx> { + fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result { + self.start.fmt(fmt)?; + write!(fmt, "..")?; + self.end.fmt(fmt)?; + Ok(()) + } +} + +impl<Idx: PartialOrd<Idx>> Range<Idx> { + /// Returns `true` if `item` is contained in the range. + /// + /// # Examples + /// + /// ``` + /// assert!(!(3..5).contains(&2)); + /// assert!( (3..5).contains(&3)); + /// assert!( (3..5).contains(&4)); + /// assert!(!(3..5).contains(&5)); + /// + /// assert!(!(3..3).contains(&3)); + /// assert!(!(3..2).contains(&3)); + /// + /// assert!( (0.0..1.0).contains(&0.5)); + /// assert!(!(0.0..1.0).contains(&f32::NAN)); + /// assert!(!(0.0..f32::NAN).contains(&0.5)); + /// assert!(!(f32::NAN..1.0).contains(&0.5)); + /// ``` + #[stable(feature = "range_contains", since = "1.35.0")] + pub fn contains<U>(&self, item: &U) -> bool + where + Idx: PartialOrd<U>, + U: ?Sized + PartialOrd<Idx>, + { + <Self as RangeBounds<Idx>>::contains(self, item) + } + + /// Returns `true` if the range contains no items. + /// + /// # Examples + /// + /// ``` + /// assert!(!(3..5).is_empty()); + /// assert!( (3..3).is_empty()); + /// assert!( (3..2).is_empty()); + /// ``` + /// + /// The range is empty if either side is incomparable: + /// + /// ``` + /// assert!(!(3.0..5.0).is_empty()); + /// assert!( (3.0..f32::NAN).is_empty()); + /// assert!( (f32::NAN..5.0).is_empty()); + /// ``` + #[stable(feature = "range_is_empty", since = "1.47.0")] + pub fn is_empty(&self) -> bool { + !(self.start < self.end) + } +} + +/// A range only bounded inclusively below (`start..`). +/// +/// The `RangeFrom` `start..` contains all values with `x >= start`. +/// +/// *Note*: Overflow in the [`Iterator`] implementation (when the contained +/// data type reaches its numerical limit) is allowed to panic, wrap, or +/// saturate. This behavior is defined by the implementation of the [`Step`] +/// trait. For primitive integers, this follows the normal rules, and respects +/// the overflow checks profile (panic in debug, wrap in release). Note also +/// that overflow happens earlier than you might assume: the overflow happens +/// in the call to `next` that yields the maximum value, as the range must be +/// set to a state to yield the next value. +/// +/// [`Step`]: crate::iter::Step +/// +/// # Examples +/// +/// The `start..` syntax is a `RangeFrom`: +/// +/// ``` +/// assert_eq!((2..), std::ops::RangeFrom { start: 2 }); +/// assert_eq!(2 + 3 + 4, (2..).take(3).sum()); +/// ``` +/// +/// ``` +/// let arr = [0, 1, 2, 3, 4]; +/// assert_eq!(arr[ .. ], [0, 1, 2, 3, 4]); +/// assert_eq!(arr[ .. 3], [0, 1, 2 ]); +/// assert_eq!(arr[ ..=3], [0, 1, 2, 3 ]); +/// assert_eq!(arr[1.. ], [ 1, 2, 3, 4]); // This is a `RangeFrom` +/// assert_eq!(arr[1.. 3], [ 1, 2 ]); +/// assert_eq!(arr[1..=3], [ 1, 2, 3 ]); +/// ``` +#[lang = "RangeFrom"] +#[doc(alias = "..")] +#[derive(Clone, PartialEq, Eq, Hash)] // not Copy -- see #27186 +#[stable(feature = "rust1", since = "1.0.0")] +pub struct RangeFrom<Idx> { + /// The lower bound of the range (inclusive). + #[stable(feature = "rust1", since = "1.0.0")] + pub start: Idx, +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl<Idx: fmt::Debug> fmt::Debug for RangeFrom<Idx> { + fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result { + self.start.fmt(fmt)?; + write!(fmt, "..")?; + Ok(()) + } +} + +impl<Idx: PartialOrd<Idx>> RangeFrom<Idx> { + /// Returns `true` if `item` is contained in the range. + /// + /// # Examples + /// + /// ``` + /// assert!(!(3..).contains(&2)); + /// assert!( (3..).contains(&3)); + /// assert!( (3..).contains(&1_000_000_000)); + /// + /// assert!( (0.0..).contains(&0.5)); + /// assert!(!(0.0..).contains(&f32::NAN)); + /// assert!(!(f32::NAN..).contains(&0.5)); + /// ``` + #[stable(feature = "range_contains", since = "1.35.0")] + pub fn contains<U>(&self, item: &U) -> bool + where + Idx: PartialOrd<U>, + U: ?Sized + PartialOrd<Idx>, + { + <Self as RangeBounds<Idx>>::contains(self, item) + } +} + +/// A range only bounded exclusively above (`..end`). +/// +/// The `RangeTo` `..end` contains all values with `x < end`. +/// It cannot serve as an [`Iterator`] because it doesn't have a starting point. +/// +/// # Examples +/// +/// The `..end` syntax is a `RangeTo`: +/// +/// ``` +/// assert_eq!((..5), std::ops::RangeTo { end: 5 }); +/// ``` +/// +/// It does not have an [`IntoIterator`] implementation, so you can't use it in +/// a `for` loop directly. This won't compile: +/// +/// ```compile_fail,E0277 +/// // error[E0277]: the trait bound `std::ops::RangeTo<{integer}>: +/// // std::iter::Iterator` is not satisfied +/// for i in ..5 { +/// // ... +/// } +/// ``` +/// +/// When used as a [slicing index], `RangeTo` produces a slice of all array +/// elements before the index indicated by `end`. +/// +/// ``` +/// let arr = [0, 1, 2, 3, 4]; +/// assert_eq!(arr[ .. ], [0, 1, 2, 3, 4]); +/// assert_eq!(arr[ .. 3], [0, 1, 2 ]); // This is a `RangeTo` +/// assert_eq!(arr[ ..=3], [0, 1, 2, 3 ]); +/// assert_eq!(arr[1.. ], [ 1, 2, 3, 4]); +/// assert_eq!(arr[1.. 3], [ 1, 2 ]); +/// assert_eq!(arr[1..=3], [ 1, 2, 3 ]); +/// ``` +/// +/// [slicing index]: crate::slice::SliceIndex +#[lang = "RangeTo"] +#[doc(alias = "..")] +#[derive(Copy, Clone, PartialEq, Eq, Hash)] +#[stable(feature = "rust1", since = "1.0.0")] +pub struct RangeTo<Idx> { + /// The upper bound of the range (exclusive). + #[stable(feature = "rust1", since = "1.0.0")] + pub end: Idx, +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl<Idx: fmt::Debug> fmt::Debug for RangeTo<Idx> { + fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result { + write!(fmt, "..")?; + self.end.fmt(fmt)?; + Ok(()) + } +} + +impl<Idx: PartialOrd<Idx>> RangeTo<Idx> { + /// Returns `true` if `item` is contained in the range. + /// + /// # Examples + /// + /// ``` + /// assert!( (..5).contains(&-1_000_000_000)); + /// assert!( (..5).contains(&4)); + /// assert!(!(..5).contains(&5)); + /// + /// assert!( (..1.0).contains(&0.5)); + /// assert!(!(..1.0).contains(&f32::NAN)); + /// assert!(!(..f32::NAN).contains(&0.5)); + /// ``` + #[stable(feature = "range_contains", since = "1.35.0")] + pub fn contains<U>(&self, item: &U) -> bool + where + Idx: PartialOrd<U>, + U: ?Sized + PartialOrd<Idx>, + { + <Self as RangeBounds<Idx>>::contains(self, item) + } +} + +/// A range bounded inclusively below and above (`start..=end`). +/// +/// The `RangeInclusive` `start..=end` contains all values with `x >= start` +/// and `x <= end`. It is empty unless `start <= end`. +/// +/// This iterator is [fused], but the specific values of `start` and `end` after +/// iteration has finished are **unspecified** other than that [`.is_empty()`] +/// will return `true` once no more values will be produced. +/// +/// [fused]: crate::iter::FusedIterator +/// [`.is_empty()`]: RangeInclusive::is_empty +/// +/// # Examples +/// +/// The `start..=end` syntax is a `RangeInclusive`: +/// +/// ``` +/// assert_eq!((3..=5), std::ops::RangeInclusive::new(3, 5)); +/// assert_eq!(3 + 4 + 5, (3..=5).sum()); +/// ``` +/// +/// ``` +/// let arr = [0, 1, 2, 3, 4]; +/// assert_eq!(arr[ .. ], [0, 1, 2, 3, 4]); +/// assert_eq!(arr[ .. 3], [0, 1, 2 ]); +/// assert_eq!(arr[ ..=3], [0, 1, 2, 3 ]); +/// assert_eq!(arr[1.. ], [ 1, 2, 3, 4]); +/// assert_eq!(arr[1.. 3], [ 1, 2 ]); +/// assert_eq!(arr[1..=3], [ 1, 2, 3 ]); // This is a `RangeInclusive` +/// ``` +#[lang = "RangeInclusive"] +#[doc(alias = "..=")] +#[derive(Clone, PartialEq, Eq, Hash)] // not Copy -- see #27186 +#[stable(feature = "inclusive_range", since = "1.26.0")] +pub struct RangeInclusive<Idx> { + // Note that the fields here are not public to allow changing the + // representation in the future; in particular, while we could plausibly + // expose start/end, modifying them without changing (future/current) + // private fields may lead to incorrect behavior, so we don't want to + // support that mode. + pub(crate) start: Idx, + pub(crate) end: Idx, + + // This field is: + // - `false` upon construction + // - `false` when iteration has yielded an element and the iterator is not exhausted + // - `true` when iteration has been used to exhaust the iterator + // + // This is required to support PartialEq and Hash without a PartialOrd bound or specialization. + pub(crate) exhausted: bool, +} + +impl<Idx> RangeInclusive<Idx> { + /// Creates a new inclusive range. Equivalent to writing `start..=end`. + /// + /// # Examples + /// + /// ``` + /// use std::ops::RangeInclusive; + /// + /// assert_eq!(3..=5, RangeInclusive::new(3, 5)); + /// ``` + #[lang = "range_inclusive_new"] + #[stable(feature = "inclusive_range_methods", since = "1.27.0")] + #[inline] + #[rustc_promotable] + #[rustc_const_stable(feature = "const_range_new", since = "1.32.0")] + pub const fn new(start: Idx, end: Idx) -> Self { + Self { start, end, exhausted: false } + } + + /// Returns the lower bound of the range (inclusive). + /// + /// When using an inclusive range for iteration, the values of `start()` and + /// [`end()`] are unspecified after the iteration ended. To determine + /// whether the inclusive range is empty, use the [`is_empty()`] method + /// instead of comparing `start() > end()`. + /// + /// Note: the value returned by this method is unspecified after the range + /// has been iterated to exhaustion. + /// + /// [`end()`]: RangeInclusive::end + /// [`is_empty()`]: RangeInclusive::is_empty + /// + /// # Examples + /// + /// ``` + /// assert_eq!((3..=5).start(), &3); + /// ``` + #[stable(feature = "inclusive_range_methods", since = "1.27.0")] + #[rustc_const_stable(feature = "const_inclusive_range_methods", since = "1.32.0")] + #[inline] + pub const fn start(&self) -> &Idx { + &self.start + } + + /// Returns the upper bound of the range (inclusive). + /// + /// When using an inclusive range for iteration, the values of [`start()`] + /// and `end()` are unspecified after the iteration ended. To determine + /// whether the inclusive range is empty, use the [`is_empty()`] method + /// instead of comparing `start() > end()`. + /// + /// Note: the value returned by this method is unspecified after the range + /// has been iterated to exhaustion. + /// + /// [`start()`]: RangeInclusive::start + /// [`is_empty()`]: RangeInclusive::is_empty + /// + /// # Examples + /// + /// ``` + /// assert_eq!((3..=5).end(), &5); + /// ``` + #[stable(feature = "inclusive_range_methods", since = "1.27.0")] + #[rustc_const_stable(feature = "const_inclusive_range_methods", since = "1.32.0")] + #[inline] + pub const fn end(&self) -> &Idx { + &self.end + } + + /// Destructures the `RangeInclusive` into (lower bound, upper (inclusive) bound). + /// + /// Note: the value returned by this method is unspecified after the range + /// has been iterated to exhaustion. + /// + /// # Examples + /// + /// ``` + /// assert_eq!((3..=5).into_inner(), (3, 5)); + /// ``` + #[stable(feature = "inclusive_range_methods", since = "1.27.0")] + #[inline] + pub fn into_inner(self) -> (Idx, Idx) { + (self.start, self.end) + } +} + +impl RangeInclusive<usize> { + /// Converts to an exclusive `Range` for `SliceIndex` implementations. + /// The caller is responsible for dealing with `end == usize::MAX`. + #[inline] + pub(crate) const fn into_slice_range(self) -> Range<usize> { + // If we're not exhausted, we want to simply slice `start..end + 1`. + // If we are exhausted, then slicing with `end + 1..end + 1` gives us an + // empty range that is still subject to bounds-checks for that endpoint. + let exclusive_end = self.end + 1; + let start = if self.exhausted { exclusive_end } else { self.start }; + start..exclusive_end + } +} + +#[stable(feature = "inclusive_range", since = "1.26.0")] +impl<Idx: fmt::Debug> fmt::Debug for RangeInclusive<Idx> { + fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result { + self.start.fmt(fmt)?; + write!(fmt, "..=")?; + self.end.fmt(fmt)?; + if self.exhausted { + write!(fmt, " (exhausted)")?; + } + Ok(()) + } +} + +impl<Idx: PartialOrd<Idx>> RangeInclusive<Idx> { + /// Returns `true` if `item` is contained in the range. + /// + /// # Examples + /// + /// ``` + /// assert!(!(3..=5).contains(&2)); + /// assert!( (3..=5).contains(&3)); + /// assert!( (3..=5).contains(&4)); + /// assert!( (3..=5).contains(&5)); + /// assert!(!(3..=5).contains(&6)); + /// + /// assert!( (3..=3).contains(&3)); + /// assert!(!(3..=2).contains(&3)); + /// + /// assert!( (0.0..=1.0).contains(&1.0)); + /// assert!(!(0.0..=1.0).contains(&f32::NAN)); + /// assert!(!(0.0..=f32::NAN).contains(&0.0)); + /// assert!(!(f32::NAN..=1.0).contains(&1.0)); + /// ``` + /// + /// This method always returns `false` after iteration has finished: + /// + /// ``` + /// let mut r = 3..=5; + /// assert!(r.contains(&3) && r.contains(&5)); + /// for _ in r.by_ref() {} + /// // Precise field values are unspecified here + /// assert!(!r.contains(&3) && !r.contains(&5)); + /// ``` + #[stable(feature = "range_contains", since = "1.35.0")] + pub fn contains<U>(&self, item: &U) -> bool + where + Idx: PartialOrd<U>, + U: ?Sized + PartialOrd<Idx>, + { + <Self as RangeBounds<Idx>>::contains(self, item) + } + + /// Returns `true` if the range contains no items. + /// + /// # Examples + /// + /// ``` + /// assert!(!(3..=5).is_empty()); + /// assert!(!(3..=3).is_empty()); + /// assert!( (3..=2).is_empty()); + /// ``` + /// + /// The range is empty if either side is incomparable: + /// + /// ``` + /// assert!(!(3.0..=5.0).is_empty()); + /// assert!( (3.0..=f32::NAN).is_empty()); + /// assert!( (f32::NAN..=5.0).is_empty()); + /// ``` + /// + /// This method returns `true` after iteration has finished: + /// + /// ``` + /// let mut r = 3..=5; + /// for _ in r.by_ref() {} + /// // Precise field values are unspecified here + /// assert!(r.is_empty()); + /// ``` + #[stable(feature = "range_is_empty", since = "1.47.0")] + #[inline] + pub fn is_empty(&self) -> bool { + self.exhausted || !(self.start <= self.end) + } +} + +/// A range only bounded inclusively above (`..=end`). +/// +/// The `RangeToInclusive` `..=end` contains all values with `x <= end`. +/// It cannot serve as an [`Iterator`] because it doesn't have a starting point. +/// +/// # Examples +/// +/// The `..=end` syntax is a `RangeToInclusive`: +/// +/// ``` +/// assert_eq!((..=5), std::ops::RangeToInclusive{ end: 5 }); +/// ``` +/// +/// It does not have an [`IntoIterator`] implementation, so you can't use it in a +/// `for` loop directly. This won't compile: +/// +/// ```compile_fail,E0277 +/// // error[E0277]: the trait bound `std::ops::RangeToInclusive<{integer}>: +/// // std::iter::Iterator` is not satisfied +/// for i in ..=5 { +/// // ... +/// } +/// ``` +/// +/// When used as a [slicing index], `RangeToInclusive` produces a slice of all +/// array elements up to and including the index indicated by `end`. +/// +/// ``` +/// let arr = [0, 1, 2, 3, 4]; +/// assert_eq!(arr[ .. ], [0, 1, 2, 3, 4]); +/// assert_eq!(arr[ .. 3], [0, 1, 2 ]); +/// assert_eq!(arr[ ..=3], [0, 1, 2, 3 ]); // This is a `RangeToInclusive` +/// assert_eq!(arr[1.. ], [ 1, 2, 3, 4]); +/// assert_eq!(arr[1.. 3], [ 1, 2 ]); +/// assert_eq!(arr[1..=3], [ 1, 2, 3 ]); +/// ``` +/// +/// [slicing index]: crate::slice::SliceIndex +#[lang = "RangeToInclusive"] +#[doc(alias = "..=")] +#[derive(Copy, Clone, PartialEq, Eq, Hash)] +#[stable(feature = "inclusive_range", since = "1.26.0")] +pub struct RangeToInclusive<Idx> { + /// The upper bound of the range (inclusive) + #[stable(feature = "inclusive_range", since = "1.26.0")] + pub end: Idx, +} + +#[stable(feature = "inclusive_range", since = "1.26.0")] +impl<Idx: fmt::Debug> fmt::Debug for RangeToInclusive<Idx> { + fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result { + write!(fmt, "..=")?; + self.end.fmt(fmt)?; + Ok(()) + } +} + +impl<Idx: PartialOrd<Idx>> RangeToInclusive<Idx> { + /// Returns `true` if `item` is contained in the range. + /// + /// # Examples + /// + /// ``` + /// assert!( (..=5).contains(&-1_000_000_000)); + /// assert!( (..=5).contains(&5)); + /// assert!(!(..=5).contains(&6)); + /// + /// assert!( (..=1.0).contains(&1.0)); + /// assert!(!(..=1.0).contains(&f32::NAN)); + /// assert!(!(..=f32::NAN).contains(&0.5)); + /// ``` + #[stable(feature = "range_contains", since = "1.35.0")] + pub fn contains<U>(&self, item: &U) -> bool + where + Idx: PartialOrd<U>, + U: ?Sized + PartialOrd<Idx>, + { + <Self as RangeBounds<Idx>>::contains(self, item) + } +} + +// RangeToInclusive<Idx> cannot impl From<RangeTo<Idx>> +// because underflow would be possible with (..0).into() + +/// An endpoint of a range of keys. +/// +/// # Examples +/// +/// `Bound`s are range endpoints: +/// +/// ``` +/// use std::ops::Bound::*; +/// use std::ops::RangeBounds; +/// +/// assert_eq!((..100).start_bound(), Unbounded); +/// assert_eq!((1..12).start_bound(), Included(&1)); +/// assert_eq!((1..12).end_bound(), Excluded(&12)); +/// ``` +/// +/// Using a tuple of `Bound`s as an argument to [`BTreeMap::range`]. +/// Note that in most cases, it's better to use range syntax (`1..5`) instead. +/// +/// ``` +/// use std::collections::BTreeMap; +/// use std::ops::Bound::{Excluded, Included, Unbounded}; +/// +/// let mut map = BTreeMap::new(); +/// map.insert(3, "a"); +/// map.insert(5, "b"); +/// map.insert(8, "c"); +/// +/// for (key, value) in map.range((Excluded(3), Included(8))) { +/// println!("{key}: {value}"); +/// } +/// +/// assert_eq!(Some((&3, &"a")), map.range((Unbounded, Included(5))).next()); +/// ``` +/// +/// [`BTreeMap::range`]: ../../std/collections/btree_map/struct.BTreeMap.html#method.range +#[stable(feature = "collections_bound", since = "1.17.0")] +#[derive(Clone, Copy, Debug, Hash, PartialEq, Eq)] +pub enum Bound<T> { + /// An inclusive bound. + #[stable(feature = "collections_bound", since = "1.17.0")] + Included(#[stable(feature = "collections_bound", since = "1.17.0")] T), + /// An exclusive bound. + #[stable(feature = "collections_bound", since = "1.17.0")] + Excluded(#[stable(feature = "collections_bound", since = "1.17.0")] T), + /// An infinite endpoint. Indicates that there is no bound in this direction. + #[stable(feature = "collections_bound", since = "1.17.0")] + Unbounded, +} + +impl<T> Bound<T> { + /// Converts from `&Bound<T>` to `Bound<&T>`. + #[inline] + #[unstable(feature = "bound_as_ref", issue = "80996")] + pub fn as_ref(&self) -> Bound<&T> { + match *self { + Included(ref x) => Included(x), + Excluded(ref x) => Excluded(x), + Unbounded => Unbounded, + } + } + + /// Converts from `&mut Bound<T>` to `Bound<&mut T>`. + #[inline] + #[unstable(feature = "bound_as_ref", issue = "80996")] + pub fn as_mut(&mut self) -> Bound<&mut T> { + match *self { + Included(ref mut x) => Included(x), + Excluded(ref mut x) => Excluded(x), + Unbounded => Unbounded, + } + } + + /// Maps a `Bound<T>` to a `Bound<U>` by applying a function to the contained value (including + /// both `Included` and `Excluded`), returning a `Bound` of the same kind. + /// + /// # Examples + /// + /// ``` + /// #![feature(bound_map)] + /// use std::ops::Bound::*; + /// + /// let bound_string = Included("Hello, World!"); + /// + /// assert_eq!(bound_string.map(|s| s.len()), Included(13)); + /// ``` + /// + /// ``` + /// #![feature(bound_map)] + /// use std::ops::Bound; + /// use Bound::*; + /// + /// let unbounded_string: Bound<String> = Unbounded; + /// + /// assert_eq!(unbounded_string.map(|s| s.len()), Unbounded); + /// ``` + #[inline] + #[unstable(feature = "bound_map", issue = "86026")] + pub fn map<U, F: FnOnce(T) -> U>(self, f: F) -> Bound<U> { + match self { + Unbounded => Unbounded, + Included(x) => Included(f(x)), + Excluded(x) => Excluded(f(x)), + } + } +} + +impl<T: Clone> Bound<&T> { + /// Map a `Bound<&T>` to a `Bound<T>` by cloning the contents of the bound. + /// + /// # Examples + /// + /// ``` + /// use std::ops::Bound::*; + /// use std::ops::RangeBounds; + /// + /// assert_eq!((1..12).start_bound(), Included(&1)); + /// assert_eq!((1..12).start_bound().cloned(), Included(1)); + /// ``` + #[must_use = "`self` will be dropped if the result is not used"] + #[stable(feature = "bound_cloned", since = "1.55.0")] + pub fn cloned(self) -> Bound<T> { + match self { + Bound::Unbounded => Bound::Unbounded, + Bound::Included(x) => Bound::Included(x.clone()), + Bound::Excluded(x) => Bound::Excluded(x.clone()), + } + } +} + +/// `RangeBounds` is implemented by Rust's built-in range types, produced +/// by range syntax like `..`, `a..`, `..b`, `..=c`, `d..e`, or `f..=g`. +#[stable(feature = "collections_range", since = "1.28.0")] +pub trait RangeBounds<T: ?Sized> { + /// Start index bound. + /// + /// Returns the start value as a `Bound`. + /// + /// # 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>; + + /// End index bound. + /// + /// Returns the end value as a `Bound`. + /// + /// # 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>; + + /// Returns `true` if `item` is contained in the range. + /// + /// # Examples + /// + /// ``` + /// assert!( (3..5).contains(&4)); + /// assert!(!(3..5).contains(&2)); + /// + /// assert!( (0.0..1.0).contains(&0.5)); + /// assert!(!(0.0..1.0).contains(&f32::NAN)); + /// assert!(!(0.0..f32::NAN).contains(&0.5)); + /// assert!(!(f32::NAN..1.0).contains(&0.5)); + #[stable(feature = "range_contains", since = "1.35.0")] + fn contains<U>(&self, item: &U) -> bool + where + T: PartialOrd<U>, + U: ?Sized + PartialOrd<T>, + { + (match self.start_bound() { + Included(start) => start <= item, + Excluded(start) => start < item, + Unbounded => true, + }) && (match self.end_bound() { + Included(end) => item <= end, + Excluded(end) => item < end, + Unbounded => true, + }) + } +} + +use self::Bound::{Excluded, Included, Unbounded}; + +#[stable(feature = "collections_range", since = "1.28.0")] +impl<T: ?Sized> RangeBounds<T> for RangeFull { + fn start_bound(&self) -> Bound<&T> { + Unbounded + } + fn end_bound(&self) -> Bound<&T> { + Unbounded + } +} + +#[stable(feature = "collections_range", since = "1.28.0")] +impl<T> RangeBounds<T> for RangeFrom<T> { + fn start_bound(&self) -> Bound<&T> { + Included(&self.start) + } + fn end_bound(&self) -> Bound<&T> { + Unbounded + } +} + +#[stable(feature = "collections_range", since = "1.28.0")] +impl<T> RangeBounds<T> for RangeTo<T> { + fn start_bound(&self) -> Bound<&T> { + Unbounded + } + fn end_bound(&self) -> Bound<&T> { + Excluded(&self.end) + } +} + +#[stable(feature = "collections_range", since = "1.28.0")] +impl<T> RangeBounds<T> for Range<T> { + fn start_bound(&self) -> Bound<&T> { + Included(&self.start) + } + fn end_bound(&self) -> Bound<&T> { + Excluded(&self.end) + } +} + +#[stable(feature = "collections_range", since = "1.28.0")] +impl<T> RangeBounds<T> for RangeInclusive<T> { + fn start_bound(&self) -> Bound<&T> { + Included(&self.start) + } + fn end_bound(&self) -> Bound<&T> { + if self.exhausted { + // When the iterator is exhausted, we usually have start == end, + // but we want the range to appear empty, containing nothing. + Excluded(&self.end) + } else { + Included(&self.end) + } + } +} + +#[stable(feature = "collections_range", since = "1.28.0")] +impl<T> RangeBounds<T> for RangeToInclusive<T> { + fn start_bound(&self) -> Bound<&T> { + Unbounded + } + fn end_bound(&self) -> Bound<&T> { + Included(&self.end) + } +} + +#[stable(feature = "collections_range", since = "1.28.0")] +impl<T> RangeBounds<T> for (Bound<T>, Bound<T>) { + fn start_bound(&self) -> Bound<&T> { + match *self { + (Included(ref start), _) => Included(start), + (Excluded(ref start), _) => Excluded(start), + (Unbounded, _) => Unbounded, + } + } + + fn end_bound(&self) -> Bound<&T> { + match *self { + (_, Included(ref end)) => Included(end), + (_, Excluded(ref end)) => Excluded(end), + (_, Unbounded) => Unbounded, + } + } +} + +#[stable(feature = "collections_range", since = "1.28.0")] +impl<'a, T: ?Sized + 'a> RangeBounds<T> for (Bound<&'a T>, Bound<&'a T>) { + fn start_bound(&self) -> Bound<&T> { + self.0 + } + + fn end_bound(&self) -> Bound<&T> { + self.1 + } +} + +#[stable(feature = "collections_range", since = "1.28.0")] +impl<T> RangeBounds<T> for RangeFrom<&T> { + fn start_bound(&self) -> Bound<&T> { + Included(self.start) + } + fn end_bound(&self) -> Bound<&T> { + Unbounded + } +} + +#[stable(feature = "collections_range", since = "1.28.0")] +impl<T> RangeBounds<T> for RangeTo<&T> { + fn start_bound(&self) -> Bound<&T> { + Unbounded + } + fn end_bound(&self) -> Bound<&T> { + Excluded(self.end) + } +} + +#[stable(feature = "collections_range", since = "1.28.0")] +impl<T> RangeBounds<T> for Range<&T> { + fn start_bound(&self) -> Bound<&T> { + Included(self.start) + } + fn end_bound(&self) -> Bound<&T> { + Excluded(self.end) + } +} + +#[stable(feature = "collections_range", since = "1.28.0")] +impl<T> RangeBounds<T> for RangeInclusive<&T> { + fn start_bound(&self) -> Bound<&T> { + Included(self.start) + } + fn end_bound(&self) -> Bound<&T> { + Included(self.end) + } +} + +#[stable(feature = "collections_range", since = "1.28.0")] +impl<T> RangeBounds<T> for RangeToInclusive<&T> { + fn start_bound(&self) -> Bound<&T> { + Unbounded + } + fn end_bound(&self) -> Bound<&T> { + Included(self.end) + } +} + +/// `OneSidedRange` is implemented for built-in range types that are unbounded +/// on one side. For example, `a..`, `..b` and `..=c` implement `OneSidedRange`, +/// but `..`, `d..e`, and `f..=g` do not. +/// +/// Types that implement `OneSidedRange<T>` must return `Bound::Unbounded` +/// from one of `RangeBounds::start_bound` or `RangeBounds::end_bound`. +#[unstable(feature = "one_sided_range", issue = "69780")] +pub trait OneSidedRange<T: ?Sized>: RangeBounds<T> {} + +#[unstable(feature = "one_sided_range", issue = "69780")] +impl<T> OneSidedRange<T> for RangeTo<T> where Self: RangeBounds<T> {} + +#[unstable(feature = "one_sided_range", issue = "69780")] +impl<T> OneSidedRange<T> for RangeFrom<T> where Self: RangeBounds<T> {} + +#[unstable(feature = "one_sided_range", issue = "69780")] +impl<T> OneSidedRange<T> for RangeToInclusive<T> where Self: RangeBounds<T> {} |