add slice take methods
This commit is contained in:
Ibraheem Ahmed
parent
e90c5fbbc5
commit
8db85a3c78
@ -181,6 +181,9 @@
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#[stable(feature = "inclusive_range", since = "1.26.0")]
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pub use self::range::{Bound, RangeBounds, RangeInclusive, RangeToInclusive};
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#[unstable(feature = "one_sided_range", issue = "69780")]
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pub use self::range::OneSidedRange;
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#[unstable(feature = "try_trait_v2", issue = "84277")]
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pub use self::try_trait::{FromResidual, Try};
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@ -971,3 +971,21 @@ fn end_bound(&self) -> Bound<&T> {
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Included(self.end)
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}
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}
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/// `OneSidedRange` is implemented for built-in range types that are unbounded
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/// on one side. For example, `a..`, `..b` and `..=c` implement `OneSidedRange`,
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/// but `..`, `d..e`, and `f..=g` do not.
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///
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/// Types that implement `OneSidedRange<T>` must return `Bound::Unbounded`
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/// from one of `RangeBounds::start_bound` or `RangeBounds::end_bound`.
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#[unstable(feature = "one_sided_range", issue = "69780")]
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pub trait OneSidedRange<T: ?Sized>: RangeBounds<T> {}
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#[unstable(feature = "one_sided_range", issue = "69780")]
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impl<T> OneSidedRange<T> for RangeTo<T> where Self: RangeBounds<T> {}
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#[unstable(feature = "one_sided_range", issue = "69780")]
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impl<T> OneSidedRange<T> for RangeFrom<T> where Self: RangeBounds<T> {}
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#[unstable(feature = "one_sided_range", issue = "69780")]
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impl<T> OneSidedRange<T> for RangeToInclusive<T> where Self: RangeBounds<T> {}
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@ -10,7 +10,7 @@
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use crate::marker::Copy;
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use crate::mem;
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use crate::num::NonZeroUsize;
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use crate::ops::{FnMut, Range, RangeBounds};
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use crate::ops::{Bound, FnMut, OneSidedRange, Range, RangeBounds};
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use crate::option::Option;
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use crate::option::Option::{None, Some};
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use crate::ptr;
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@ -82,6 +82,29 @@
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#[unstable(feature = "inherent_ascii_escape", issue = "77174")]
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pub use ascii::EscapeAscii;
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/// Calculates the direction and split point of a one-sided range.
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///
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/// This is a helper function for `take` and `take_mut` that returns
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/// the direction of the split (front or back) as well as the index at
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/// which to split. Returns `None` if the split index would overflow.
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#[inline]
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fn split_point_of(range: impl OneSidedRange<usize>) -> Option<(Direction, usize)> {
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use Bound::*;
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Some(match (range.start_bound(), range.end_bound()) {
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(Unbounded, Excluded(i)) => (Direction::Front, *i),
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(Unbounded, Included(i)) => (Direction::Front, i.checked_add(1)?),
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(Excluded(i), Unbounded) => (Direction::Back, i.checked_add(1)?),
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(Included(i), Unbounded) => (Direction::Back, *i),
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_ => unreachable!(),
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})
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}
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enum Direction {
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Front,
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Back,
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}
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#[lang = "slice"]
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#[cfg(not(test))]
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impl<T> [T] {
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@ -3576,6 +3599,245 @@ pub fn partition_point<P>(&self, mut pred: P) -> usize
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{
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self.binary_search_by(|x| if pred(x) { Less } else { Greater }).unwrap_or_else(|i| i)
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}
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/// Removes the subslice corresponding to the given range
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/// and returns a reference to it.
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///
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/// Returns `None` and does not modify the slice if the given
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/// range is out of bounds.
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///
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/// Note that this method only accepts one-sided ranges such as
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/// `2..` or `..6`, but not `2..6`.
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///
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/// # Examples
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///
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/// Taking the first three elements of a slice:
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///
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/// ```
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/// #![feature(slice_take)]
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///
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/// let mut slice: &[_] = &['a', 'b', 'c', 'd'];
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/// let mut first_three = slice.take(..3).unwrap();
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///
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/// assert_eq!(slice, &['d']);
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/// assert_eq!(first_three, &['a', 'b', 'c']);
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/// ```
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///
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/// Taking the last two elements of a slice:
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///
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/// ```
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/// #![feature(slice_take)]
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///
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/// let mut slice: &[_] = &['a', 'b', 'c', 'd'];
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/// let mut tail = slice.take(2..).unwrap();
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///
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/// assert_eq!(slice, &['a', 'b']);
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/// assert_eq!(tail, &['c', 'd']);
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/// ```
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///
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/// Getting `None` when `range` is out of bounds:
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///
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/// ```
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/// #![feature(slice_take)]
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///
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/// let mut slice: &[_] = &['a', 'b', 'c', 'd'];
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///
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/// assert_eq!(None, slice.take(5..));
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/// assert_eq!(None, slice.take(..5));
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/// assert_eq!(None, slice.take(..=4));
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/// let expected: &[char] = &['a', 'b', 'c', 'd'];
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/// assert_eq!(Some(expected), slice.take(..4));
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/// ```
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#[inline]
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#[must_use = "method does not modify the slice if the range is out of bounds"]
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#[unstable(feature = "slice_take", issue = "62280")]
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pub fn take<'a, R: OneSidedRange<usize>>(self: &mut &'a Self, range: R) -> Option<&'a Self> {
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let (direction, split_index) = split_point_of(range)?;
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if split_index > self.len() {
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return None;
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}
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let (front, back) = self.split_at(split_index);
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match direction {
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Direction::Front => {
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*self = back;
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Some(front)
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}
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Direction::Back => {
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*self = front;
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Some(back)
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}
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}
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}
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/// Removes the subslice corresponding to the given range
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/// and returns a mutable reference to it.
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///
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/// Returns `None` and does not modify the slice if the given
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/// range is out of bounds.
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///
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/// Note that this method only accepts one-sided ranges such as
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/// `2..` or `..6`, but not `2..6`.
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///
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/// # Examples
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///
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/// Taking the first three elements of a slice:
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///
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/// ```
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/// #![feature(slice_take)]
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///
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/// let mut slice: &mut [_] = &mut ['a', 'b', 'c', 'd'];
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/// let mut first_three = slice.take_mut(..3).unwrap();
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///
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/// assert_eq!(slice, &mut ['d']);
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/// assert_eq!(first_three, &mut ['a', 'b', 'c']);
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/// ```
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///
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/// Taking the last two elements of a slice:
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///
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/// ```
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/// #![feature(slice_take)]
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///
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/// let mut slice: &mut [_] = &mut ['a', 'b', 'c', 'd'];
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/// let mut tail = slice.take_mut(2..).unwrap();
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///
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/// assert_eq!(slice, &mut ['a', 'b']);
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/// assert_eq!(tail, &mut ['c', 'd']);
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/// ```
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///
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/// Getting `None` when `range` is out of bounds:
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///
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/// ```
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/// #![feature(slice_take)]
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///
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/// let mut slice: &mut [_] = &mut ['a', 'b', 'c', 'd'];
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///
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/// assert_eq!(None, slice.take_mut(5..));
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/// assert_eq!(None, slice.take_mut(..5));
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/// assert_eq!(None, slice.take_mut(..=4));
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/// let expected: &mut [_] = &mut ['a', 'b', 'c', 'd'];
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/// assert_eq!(Some(expected), slice.take_mut(..4));
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/// ```
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#[inline]
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#[must_use = "method does not modify the slice if the range is out of bounds"]
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#[unstable(feature = "slice_take", issue = "62280")]
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pub fn take_mut<'a, R: OneSidedRange<usize>>(
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self: &mut &'a mut Self,
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range: R,
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) -> Option<&'a mut Self> {
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let (direction, split_index) = split_point_of(range)?;
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if split_index > self.len() {
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return None;
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}
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let (front, back) = mem::take(self).split_at_mut(split_index);
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match direction {
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Direction::Front => {
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*self = back;
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Some(front)
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}
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Direction::Back => {
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*self = front;
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Some(back)
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}
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}
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}
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/// Removes the first element of the slice and returns a reference
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/// to it.
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///
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/// Returns `None` if the slice is empty.
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///
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/// # Examples
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///
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/// ```
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/// #![feature(slice_take)]
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///
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/// let mut slice: &[_] = &['a', 'b', 'c'];
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/// let first = slice.take_first().unwrap();
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///
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/// assert_eq!(slice, &['b', 'c']);
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/// assert_eq!(first, &'a');
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/// ```
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#[inline]
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#[unstable(feature = "slice_take", issue = "62280")]
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pub fn take_first<'a>(self: &mut &'a Self) -> Option<&'a T> {
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let (first, rem) = self.split_first()?;
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*self = rem;
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Some(first)
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}
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/// Removes the first element of the slice and returns a mutable
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/// reference to it.
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///
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/// Returns `None` if the slice is empty.
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///
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/// # Examples
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///
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/// ```
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/// #![feature(slice_take)]
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///
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/// let mut slice: &mut [_] = &mut ['a', 'b', 'c'];
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/// let first = slice.take_first_mut().unwrap();
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/// *first = 'd';
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///
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/// assert_eq!(slice, &['b', 'c']);
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/// assert_eq!(first, &'d');
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/// ```
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#[inline]
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#[unstable(feature = "slice_take", issue = "62280")]
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pub fn take_first_mut<'a>(self: &mut &'a mut Self) -> Option<&'a mut T> {
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let (first, rem) = mem::take(self).split_first_mut()?;
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*self = rem;
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Some(first)
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}
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/// Removes the last element of the slice and returns a reference
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/// to it.
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///
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/// Returns `None` if the slice is empty.
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///
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/// # Examples
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///
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/// ```
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/// #![feature(slice_take)]
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///
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/// let mut slice: &[_] = &['a', 'b', 'c'];
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/// let last = slice.take_last().unwrap();
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///
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/// assert_eq!(slice, &['a', 'b']);
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/// assert_eq!(last, &'c');
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/// ```
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#[inline]
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#[unstable(feature = "slice_take", issue = "62280")]
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pub fn take_last<'a>(self: &mut &'a Self) -> Option<&'a T> {
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let (last, rem) = self.split_last()?;
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*self = rem;
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Some(last)
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}
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/// Removes the last element of the slice and returns a mutable
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/// reference to it.
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///
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/// Returns `None` if the slice is empty.
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///
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/// # Examples
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///
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/// ```
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/// #![feature(slice_take)]
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///
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/// let mut slice: &mut [_] = &mut ['a', 'b', 'c'];
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/// let last = slice.take_last_mut().unwrap();
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/// *last = 'd';
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///
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/// assert_eq!(slice, &['a', 'b']);
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/// assert_eq!(last, &'d');
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/// ```
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#[inline]
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#[unstable(feature = "slice_take", issue = "62280")]
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pub fn take_last_mut<'a>(self: &mut &'a mut Self) -> Option<&'a mut T> {
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let (last, rem) = mem::take(self).split_last_mut()?;
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*self = rem;
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Some(last)
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}
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}
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trait CloneFromSpec<T> {
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@ -34,6 +34,7 @@
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#![feature(pattern)]
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#![feature(sort_internals)]
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#![feature(slice_partition_at_index)]
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#![feature(slice_take)]
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#![feature(maybe_uninit_uninit_array)]
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#![feature(maybe_uninit_array_assume_init)]
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#![feature(maybe_uninit_extra)]
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@ -2232,3 +2232,112 @@ fn slice_split_array_mut_out_of_bounds() {
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v.split_array_mut::<7>();
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}
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macro_rules! take_tests {
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(slice: &[], $($tts:tt)*) => {
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take_tests!(ty: &[()], slice: &[], $($tts)*);
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};
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(slice: &mut [], $($tts:tt)*) => {
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take_tests!(ty: &mut [()], slice: &mut [], $($tts)*);
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};
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(slice: &$slice:expr, $($tts:tt)*) => {
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take_tests!(ty: &[_], slice: &$slice, $($tts)*);
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};
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(slice: &mut $slice:expr, $($tts:tt)*) => {
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take_tests!(ty: &mut [_], slice: &mut $slice, $($tts)*);
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};
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(ty: $ty:ty, slice: $slice:expr, method: $method:ident, $(($test_name:ident, ($($args:expr),*), $output:expr, $remaining:expr),)*) => {
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$(
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#[test]
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fn $test_name() {
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let mut slice: $ty = $slice;
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assert_eq!($output, slice.$method($($args)*));
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let remaining: $ty = $remaining;
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assert_eq!(remaining, slice);
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}
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)*
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};
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}
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take_tests! {
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slice: &[0, 1, 2, 3], method: take,
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(take_in_bounds_range_to, (..1), Some(&[0] as _), &[1, 2, 3]),
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(take_in_bounds_range_to_inclusive, (..=0), Some(&[0] as _), &[1, 2, 3]),
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(take_in_bounds_range_from, (2..), Some(&[2, 3] as _), &[0, 1]),
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(take_oob_range_to, (..5), None, &[0, 1, 2, 3]),
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(take_oob_range_to_inclusive, (..=4), None, &[0, 1, 2, 3]),
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(take_oob_range_from, (5..), None, &[0, 1, 2, 3]),
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}
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take_tests! {
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slice: &mut [0, 1, 2, 3], method: take_mut,
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(take_mut_in_bounds_range_to, (..1), Some(&mut [0] as _), &mut [1, 2, 3]),
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(take_mut_in_bounds_range_to_inclusive, (..=0), Some(&mut [0] as _), &mut [1, 2, 3]),
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(take_mut_in_bounds_range_from, (2..), Some(&mut [2, 3] as _), &mut [0, 1]),
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(take_mut_oob_range_to, (..5), None, &mut [0, 1, 2, 3]),
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(take_mut_oob_range_to_inclusive, (..=4), None, &mut [0, 1, 2, 3]),
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(take_mut_oob_range_from, (5..), None, &mut [0, 1, 2, 3]),
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}
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take_tests! {
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slice: &[1, 2], method: take_first,
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(take_first_nonempty, (), Some(&1), &[2]),
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}
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take_tests! {
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slice: &mut [1, 2], method: take_first_mut,
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(take_first_mut_nonempty, (), Some(&mut 1), &mut [2]),
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}
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take_tests! {
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slice: &[1, 2], method: take_last,
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(take_last_nonempty, (), Some(&2), &[1]),
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}
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take_tests! {
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slice: &mut [1, 2], method: take_last_mut,
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(take_last_mut_nonempty, (), Some(&mut 2), &mut [1]),
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}
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take_tests! {
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slice: &[], method: take_first,
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(take_first_empty, (), None, &[]),
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}
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take_tests! {
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slice: &mut [], method: take_first_mut,
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(take_first_mut_empty, (), None, &mut []),
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}
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take_tests! {
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slice: &[], method: take_last,
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(take_last_empty, (), None, &[]),
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}
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take_tests! {
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slice: &mut [], method: take_last_mut,
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(take_last_mut_empty, (), None, &mut []),
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}
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const EMPTY_MAX: &'static [()] = &[(); usize::MAX];
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// can't be a constant due to const mutability rules
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macro_rules! empty_max_mut {
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() => {
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&mut [(); usize::MAX] as _
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};
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}
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take_tests! {
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slice: &[(); usize::MAX], method: take,
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(take_in_bounds_max_range_to, (..usize::MAX), Some(EMPTY_MAX), &[(); 0]),
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(take_oob_max_range_to_inclusive, (..=usize::MAX), None, EMPTY_MAX),
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(take_in_bounds_max_range_from, (usize::MAX..), Some(&[] as _), EMPTY_MAX),
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}
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take_tests! {
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slice: &mut [(); usize::MAX], method: take_mut,
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(take_mut_in_bounds_max_range_to, (..usize::MAX), Some(empty_max_mut!()), &mut [(); 0]),
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(take_mut_oob_max_range_to_inclusive, (..=usize::MAX), None, empty_max_mut!()),
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(take_mut_in_bounds_max_range_from, (usize::MAX..), Some(&mut [] as _), empty_max_mut!()),
|
||||
}
|
||||
|
||||
Loading…
Reference in New Issue
Block a user