1 //! Slice management and manipulation.
3 //! For more details see [`std::slice`].
5 //! [`std::slice`]: ../../std/slice/index.html
7 #![stable(feature = "rust1", since = "1.0.0")]
9 use crate::cmp::Ordering::{self, Greater, Less};
10 use crate::marker::Copy;
12 use crate::num::NonZeroUsize;
13 use crate::ops::{Bound, FnMut, OneSidedRange, Range, RangeBounds};
14 use crate::option::Option;
15 use crate::option::Option::{None, Some};
17 use crate::result::Result;
18 use crate::result::Result::{Err, Ok};
19 use crate::simd::{self, Simd};
23 feature = "slice_internals",
25 reason = "exposed from core to be reused in std; use the memchr crate"
27 /// Pure rust memchr implementation, taken from rust-memchr
39 #[stable(feature = "rust1", since = "1.0.0")]
40 pub use iter::{Chunks, ChunksMut, Windows};
41 #[stable(feature = "rust1", since = "1.0.0")]
42 pub use iter::{Iter, IterMut};
43 #[stable(feature = "rust1", since = "1.0.0")]
44 pub use iter::{RSplitN, RSplitNMut, Split, SplitMut, SplitN, SplitNMut};
46 #[stable(feature = "slice_rsplit", since = "1.27.0")]
47 pub use iter::{RSplit, RSplitMut};
49 #[stable(feature = "chunks_exact", since = "1.31.0")]
50 pub use iter::{ChunksExact, ChunksExactMut};
52 #[stable(feature = "rchunks", since = "1.31.0")]
53 pub use iter::{RChunks, RChunksExact, RChunksExactMut, RChunksMut};
55 #[unstable(feature = "array_chunks", issue = "74985")]
56 pub use iter::{ArrayChunks, ArrayChunksMut};
58 #[unstable(feature = "array_windows", issue = "75027")]
59 pub use iter::ArrayWindows;
61 #[unstable(feature = "slice_group_by", issue = "80552")]
62 pub use iter::{GroupBy, GroupByMut};
64 #[stable(feature = "split_inclusive", since = "1.51.0")]
65 pub use iter::{SplitInclusive, SplitInclusiveMut};
67 #[stable(feature = "rust1", since = "1.0.0")]
68 pub use raw::{from_raw_parts, from_raw_parts_mut};
70 #[stable(feature = "from_ref", since = "1.28.0")]
71 pub use raw::{from_mut, from_ref};
73 #[unstable(feature = "slice_from_ptr_range", issue = "89792")]
74 pub use raw::{from_mut_ptr_range, from_ptr_range};
76 // This function is public only because there is no other way to unit test heapsort.
77 #[unstable(feature = "sort_internals", reason = "internal to sort module", issue = "none")]
78 pub use sort::heapsort;
80 #[stable(feature = "slice_get_slice", since = "1.28.0")]
81 pub use index::SliceIndex;
83 #[unstable(feature = "slice_range", issue = "76393")]
86 #[stable(feature = "inherent_ascii_escape", since = "1.60.0")]
87 pub use ascii::EscapeAscii;
89 /// Calculates the direction and split point of a one-sided range.
91 /// This is a helper function for `take` and `take_mut` that returns
92 /// the direction of the split (front or back) as well as the index at
93 /// which to split. Returns `None` if the split index would overflow.
95 fn split_point_of(range: impl OneSidedRange<usize>) -> Option<(Direction, usize)> {
98 Some(match (range.start_bound(), range.end_bound()) {
99 (Unbounded, Excluded(i)) => (Direction::Front, *i),
100 (Unbounded, Included(i)) => (Direction::Front, i.checked_add(1)?),
101 (Excluded(i), Unbounded) => (Direction::Back, i.checked_add(1)?),
102 (Included(i), Unbounded) => (Direction::Back, *i),
112 #[cfg_attr(bootstrap, lang = "slice")]
115 /// Returns the number of elements in the slice.
120 /// let a = [1, 2, 3];
121 /// assert_eq!(a.len(), 3);
123 #[lang = "slice_len_fn"]
124 #[stable(feature = "rust1", since = "1.0.0")]
125 #[rustc_const_stable(feature = "const_slice_len", since = "1.39.0")]
128 // SAFETY: const sound because we transmute out the length field as a usize (which it must be)
129 pub const fn len(&self) -> usize {
130 // FIXME: Replace with `crate::ptr::metadata(self)` when that is const-stable.
131 // As of this writing this causes a "Const-stable functions can only call other
132 // const-stable functions" error.
134 // SAFETY: Accessing the value from the `PtrRepr` union is safe since *const T
135 // and PtrComponents<T> have the same memory layouts. Only std can make this
137 unsafe { crate::ptr::PtrRepr { const_ptr: self }.components.metadata }
140 /// Returns `true` if the slice has a length of 0.
145 /// let a = [1, 2, 3];
146 /// assert!(!a.is_empty());
148 #[stable(feature = "rust1", since = "1.0.0")]
149 #[rustc_const_stable(feature = "const_slice_is_empty", since = "1.39.0")]
152 pub const fn is_empty(&self) -> bool {
156 /// Returns the first element of the slice, or `None` if it is empty.
161 /// let v = [10, 40, 30];
162 /// assert_eq!(Some(&10), v.first());
164 /// let w: &[i32] = &[];
165 /// assert_eq!(None, w.first());
167 #[stable(feature = "rust1", since = "1.0.0")]
168 #[rustc_const_stable(feature = "const_slice_first_last_not_mut", since = "1.56.0")]
171 pub const fn first(&self) -> Option<&T> {
172 if let [first, ..] = self { Some(first) } else { None }
175 /// Returns a mutable pointer to the first element of the slice, or `None` if it is empty.
180 /// let x = &mut [0, 1, 2];
182 /// if let Some(first) = x.first_mut() {
185 /// assert_eq!(x, &[5, 1, 2]);
187 #[stable(feature = "rust1", since = "1.0.0")]
188 #[rustc_const_unstable(feature = "const_slice_first_last", issue = "83570")]
191 pub const fn first_mut(&mut self) -> Option<&mut T> {
192 if let [first, ..] = self { Some(first) } else { None }
195 /// Returns the first and all the rest of the elements of the slice, or `None` if it is empty.
200 /// let x = &[0, 1, 2];
202 /// if let Some((first, elements)) = x.split_first() {
203 /// assert_eq!(first, &0);
204 /// assert_eq!(elements, &[1, 2]);
207 #[stable(feature = "slice_splits", since = "1.5.0")]
208 #[rustc_const_stable(feature = "const_slice_first_last_not_mut", since = "1.56.0")]
211 pub const fn split_first(&self) -> Option<(&T, &[T])> {
212 if let [first, tail @ ..] = self { Some((first, tail)) } else { None }
215 /// Returns the first and all the rest of the elements of the slice, or `None` if it is empty.
220 /// let x = &mut [0, 1, 2];
222 /// if let Some((first, elements)) = x.split_first_mut() {
227 /// assert_eq!(x, &[3, 4, 5]);
229 #[stable(feature = "slice_splits", since = "1.5.0")]
230 #[rustc_const_unstable(feature = "const_slice_first_last", issue = "83570")]
233 pub const fn split_first_mut(&mut self) -> Option<(&mut T, &mut [T])> {
234 if let [first, tail @ ..] = self { Some((first, tail)) } else { None }
237 /// Returns the last and all the rest of the elements of the slice, or `None` if it is empty.
242 /// let x = &[0, 1, 2];
244 /// if let Some((last, elements)) = x.split_last() {
245 /// assert_eq!(last, &2);
246 /// assert_eq!(elements, &[0, 1]);
249 #[stable(feature = "slice_splits", since = "1.5.0")]
250 #[rustc_const_stable(feature = "const_slice_first_last_not_mut", since = "1.56.0")]
253 pub const fn split_last(&self) -> Option<(&T, &[T])> {
254 if let [init @ .., last] = self { Some((last, init)) } else { None }
257 /// Returns the last and all the rest of the elements of the slice, or `None` if it is empty.
262 /// let x = &mut [0, 1, 2];
264 /// if let Some((last, elements)) = x.split_last_mut() {
269 /// assert_eq!(x, &[4, 5, 3]);
271 #[stable(feature = "slice_splits", since = "1.5.0")]
272 #[rustc_const_unstable(feature = "const_slice_first_last", issue = "83570")]
275 pub const fn split_last_mut(&mut self) -> Option<(&mut T, &mut [T])> {
276 if let [init @ .., last] = self { Some((last, init)) } else { None }
279 /// Returns the last element of the slice, or `None` if it is empty.
284 /// let v = [10, 40, 30];
285 /// assert_eq!(Some(&30), v.last());
287 /// let w: &[i32] = &[];
288 /// assert_eq!(None, w.last());
290 #[stable(feature = "rust1", since = "1.0.0")]
291 #[rustc_const_stable(feature = "const_slice_first_last_not_mut", since = "1.56.0")]
294 pub const fn last(&self) -> Option<&T> {
295 if let [.., last] = self { Some(last) } else { None }
298 /// Returns a mutable pointer to the last item in the slice.
303 /// let x = &mut [0, 1, 2];
305 /// if let Some(last) = x.last_mut() {
308 /// assert_eq!(x, &[0, 1, 10]);
310 #[stable(feature = "rust1", since = "1.0.0")]
311 #[rustc_const_unstable(feature = "const_slice_first_last", issue = "83570")]
314 pub const fn last_mut(&mut self) -> Option<&mut T> {
315 if let [.., last] = self { Some(last) } else { None }
318 /// Returns a reference to an element or subslice depending on the type of
321 /// - If given a position, returns a reference to the element at that
322 /// position or `None` if out of bounds.
323 /// - If given a range, returns the subslice corresponding to that range,
324 /// or `None` if out of bounds.
329 /// let v = [10, 40, 30];
330 /// assert_eq!(Some(&40), v.get(1));
331 /// assert_eq!(Some(&[10, 40][..]), v.get(0..2));
332 /// assert_eq!(None, v.get(3));
333 /// assert_eq!(None, v.get(0..4));
335 #[stable(feature = "rust1", since = "1.0.0")]
336 #[rustc_const_unstable(feature = "const_slice_index", issue = "none")]
339 pub const fn get<I>(&self, index: I) -> Option<&I::Output>
341 I: ~const SliceIndex<Self>,
346 /// Returns a mutable reference to an element or subslice depending on the
347 /// type of index (see [`get`]) or `None` if the index is out of bounds.
349 /// [`get`]: slice::get
354 /// let x = &mut [0, 1, 2];
356 /// if let Some(elem) = x.get_mut(1) {
359 /// assert_eq!(x, &[0, 42, 2]);
361 #[stable(feature = "rust1", since = "1.0.0")]
362 #[rustc_const_unstable(feature = "const_slice_index", issue = "none")]
365 pub const fn get_mut<I>(&mut self, index: I) -> Option<&mut I::Output>
367 I: ~const SliceIndex<Self>,
372 /// Returns a reference to an element or subslice, without doing bounds
375 /// For a safe alternative see [`get`].
379 /// Calling this method with an out-of-bounds index is *[undefined behavior]*
380 /// even if the resulting reference is not used.
382 /// [`get`]: slice::get
383 /// [undefined behavior]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
388 /// let x = &[1, 2, 4];
391 /// assert_eq!(x.get_unchecked(1), &2);
394 #[stable(feature = "rust1", since = "1.0.0")]
395 #[rustc_const_unstable(feature = "const_slice_index", issue = "none")]
398 pub const unsafe fn get_unchecked<I>(&self, index: I) -> &I::Output
400 I: ~const SliceIndex<Self>,
402 // SAFETY: the caller must uphold most of the safety requirements for `get_unchecked`;
403 // the slice is dereferenceable because `self` is a safe reference.
404 // The returned pointer is safe because impls of `SliceIndex` have to guarantee that it is.
405 unsafe { &*index.get_unchecked(self) }
408 /// Returns a mutable reference to an element or subslice, without doing
411 /// For a safe alternative see [`get_mut`].
415 /// Calling this method with an out-of-bounds index is *[undefined behavior]*
416 /// even if the resulting reference is not used.
418 /// [`get_mut`]: slice::get_mut
419 /// [undefined behavior]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
424 /// let x = &mut [1, 2, 4];
427 /// let elem = x.get_unchecked_mut(1);
430 /// assert_eq!(x, &[1, 13, 4]);
432 #[stable(feature = "rust1", since = "1.0.0")]
433 #[rustc_const_unstable(feature = "const_slice_index", issue = "none")]
436 pub const unsafe fn get_unchecked_mut<I>(&mut self, index: I) -> &mut I::Output
438 I: ~const SliceIndex<Self>,
440 // SAFETY: the caller must uphold the safety requirements for `get_unchecked_mut`;
441 // the slice is dereferenceable because `self` is a safe reference.
442 // The returned pointer is safe because impls of `SliceIndex` have to guarantee that it is.
443 unsafe { &mut *index.get_unchecked_mut(self) }
446 /// Returns a raw pointer to the slice's buffer.
448 /// The caller must ensure that the slice outlives the pointer this
449 /// function returns, or else it will end up pointing to garbage.
451 /// The caller must also ensure that the memory the pointer (non-transitively) points to
452 /// is never written to (except inside an `UnsafeCell`) using this pointer or any pointer
453 /// derived from it. If you need to mutate the contents of the slice, use [`as_mut_ptr`].
455 /// Modifying the container referenced by this slice may cause its buffer
456 /// to be reallocated, which would also make any pointers to it invalid.
461 /// let x = &[1, 2, 4];
462 /// let x_ptr = x.as_ptr();
465 /// for i in 0..x.len() {
466 /// assert_eq!(x.get_unchecked(i), &*x_ptr.add(i));
471 /// [`as_mut_ptr`]: slice::as_mut_ptr
472 #[stable(feature = "rust1", since = "1.0.0")]
473 #[rustc_const_stable(feature = "const_slice_as_ptr", since = "1.32.0")]
476 pub const fn as_ptr(&self) -> *const T {
477 self as *const [T] as *const T
480 /// Returns an unsafe mutable pointer to the slice's buffer.
482 /// The caller must ensure that the slice outlives the pointer this
483 /// function returns, or else it will end up pointing to garbage.
485 /// Modifying the container referenced by this slice may cause its buffer
486 /// to be reallocated, which would also make any pointers to it invalid.
491 /// let x = &mut [1, 2, 4];
492 /// let x_ptr = x.as_mut_ptr();
495 /// for i in 0..x.len() {
496 /// *x_ptr.add(i) += 2;
499 /// assert_eq!(x, &[3, 4, 6]);
501 #[stable(feature = "rust1", since = "1.0.0")]
502 #[rustc_const_stable(feature = "const_ptr_offset", since = "1.61.0")]
503 #[rustc_allow_const_fn_unstable(const_mut_refs)]
506 pub const fn as_mut_ptr(&mut self) -> *mut T {
507 self as *mut [T] as *mut T
510 /// Returns the two raw pointers spanning the slice.
512 /// The returned range is half-open, which means that the end pointer
513 /// points *one past* the last element of the slice. This way, an empty
514 /// slice is represented by two equal pointers, and the difference between
515 /// the two pointers represents the size of the slice.
517 /// See [`as_ptr`] for warnings on using these pointers. The end pointer
518 /// requires extra caution, as it does not point to a valid element in the
521 /// This function is useful for interacting with foreign interfaces which
522 /// use two pointers to refer to a range of elements in memory, as is
525 /// It can also be useful to check if a pointer to an element refers to an
526 /// element of this slice:
529 /// let a = [1, 2, 3];
530 /// let x = &a[1] as *const _;
531 /// let y = &5 as *const _;
533 /// assert!(a.as_ptr_range().contains(&x));
534 /// assert!(!a.as_ptr_range().contains(&y));
537 /// [`as_ptr`]: slice::as_ptr
538 #[stable(feature = "slice_ptr_range", since = "1.48.0")]
539 #[rustc_const_stable(feature = "const_ptr_offset", since = "1.61.0")]
542 pub const fn as_ptr_range(&self) -> Range<*const T> {
543 let start = self.as_ptr();
544 // SAFETY: The `add` here is safe, because:
546 // - Both pointers are part of the same object, as pointing directly
547 // past the object also counts.
549 // - The size of the slice is never larger than isize::MAX bytes, as
551 // - https://github.com/rust-lang/unsafe-code-guidelines/issues/102#issuecomment-473340447
552 // - https://doc.rust-lang.org/reference/behavior-considered-undefined.html
553 // - https://doc.rust-lang.org/core/slice/fn.from_raw_parts.html#safety
554 // (This doesn't seem normative yet, but the very same assumption is
555 // made in many places, including the Index implementation of slices.)
557 // - There is no wrapping around involved, as slices do not wrap past
558 // the end of the address space.
560 // See the documentation of pointer::add.
561 let end = unsafe { start.add(self.len()) };
565 /// Returns the two unsafe mutable pointers spanning the slice.
567 /// The returned range is half-open, which means that the end pointer
568 /// points *one past* the last element of the slice. This way, an empty
569 /// slice is represented by two equal pointers, and the difference between
570 /// the two pointers represents the size of the slice.
572 /// See [`as_mut_ptr`] for warnings on using these pointers. The end
573 /// pointer requires extra caution, as it does not point to a valid element
576 /// This function is useful for interacting with foreign interfaces which
577 /// use two pointers to refer to a range of elements in memory, as is
580 /// [`as_mut_ptr`]: slice::as_mut_ptr
581 #[stable(feature = "slice_ptr_range", since = "1.48.0")]
582 #[rustc_const_stable(feature = "const_ptr_offset", since = "1.61.0")]
583 #[rustc_allow_const_fn_unstable(const_mut_refs)]
586 pub const fn as_mut_ptr_range(&mut self) -> Range<*mut T> {
587 let start = self.as_mut_ptr();
588 // SAFETY: See as_ptr_range() above for why `add` here is safe.
589 let end = unsafe { start.add(self.len()) };
593 /// Swaps two elements in the slice.
597 /// * a - The index of the first element
598 /// * b - The index of the second element
602 /// Panics if `a` or `b` are out of bounds.
607 /// let mut v = ["a", "b", "c", "d", "e"];
609 /// assert!(v == ["a", "b", "e", "d", "c"]);
611 #[stable(feature = "rust1", since = "1.0.0")]
612 #[rustc_const_unstable(feature = "const_swap", issue = "83163")]
615 pub const fn swap(&mut self, a: usize, b: usize) {
616 // FIXME: use swap_unchecked here (https://github.com/rust-lang/rust/pull/88540#issuecomment-944344343)
617 // Can't take two mutable loans from one vector, so instead use raw pointers.
618 let pa = ptr::addr_of_mut!(self[a]);
619 let pb = ptr::addr_of_mut!(self[b]);
620 // SAFETY: `pa` and `pb` have been created from safe mutable references and refer
621 // to elements in the slice and therefore are guaranteed to be valid and aligned.
622 // Note that accessing the elements behind `a` and `b` is checked and will
623 // panic when out of bounds.
629 /// Swaps two elements in the slice, without doing bounds checking.
631 /// For a safe alternative see [`swap`].
635 /// * a - The index of the first element
636 /// * b - The index of the second element
640 /// Calling this method with an out-of-bounds index is *[undefined behavior]*.
641 /// The caller has to ensure that `a < self.len()` and `b < self.len()`.
646 /// #![feature(slice_swap_unchecked)]
648 /// let mut v = ["a", "b", "c", "d"];
649 /// // SAFETY: we know that 1 and 3 are both indices of the slice
650 /// unsafe { v.swap_unchecked(1, 3) };
651 /// assert!(v == ["a", "d", "c", "b"]);
654 /// [`swap`]: slice::swap
655 /// [undefined behavior]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
656 #[unstable(feature = "slice_swap_unchecked", issue = "88539")]
657 #[rustc_const_unstable(feature = "const_swap", issue = "83163")]
658 pub const unsafe fn swap_unchecked(&mut self, a: usize, b: usize) {
659 #[cfg(debug_assertions)]
665 let ptr = self.as_mut_ptr();
666 // SAFETY: caller has to guarantee that `a < self.len()` and `b < self.len()`
668 ptr::swap(ptr.add(a), ptr.add(b));
672 /// Reverses the order of elements in the slice, in place.
677 /// let mut v = [1, 2, 3];
679 /// assert!(v == [3, 2, 1]);
681 #[stable(feature = "rust1", since = "1.0.0")]
683 pub fn reverse(&mut self) {
684 let half_len = self.len() / 2;
685 let Range { start, end } = self.as_mut_ptr_range();
687 // These slices will skip the middle item for an odd length,
688 // since that one doesn't need to move.
689 let (front_half, back_half) =
690 // SAFETY: Both are subparts of the original slice, so the memory
691 // range is valid, and they don't overlap because they're each only
692 // half (or less) of the original slice.
695 slice::from_raw_parts_mut(start, half_len),
696 slice::from_raw_parts_mut(end.sub(half_len), half_len),
700 // Introducing a function boundary here means that the two halves
701 // get `noalias` markers, allowing better optimization as LLVM
702 // knows that they're disjoint, unlike in the original slice.
703 revswap(front_half, back_half, half_len);
706 fn revswap<T>(a: &mut [T], b: &mut [T], n: usize) {
707 debug_assert_eq!(a.len(), n);
708 debug_assert_eq!(b.len(), n);
710 // Because this function is first compiled in isolation,
711 // this check tells LLVM that the indexing below is
712 // in-bounds. Then after inlining -- once the actual
713 // lengths of the slices are known -- it's removed.
714 let (a, b) = (&mut a[..n], &mut b[..n]);
717 mem::swap(&mut a[i], &mut b[n - 1 - i]);
722 /// Returns an iterator over the slice.
727 /// let x = &[1, 2, 4];
728 /// let mut iterator = x.iter();
730 /// assert_eq!(iterator.next(), Some(&1));
731 /// assert_eq!(iterator.next(), Some(&2));
732 /// assert_eq!(iterator.next(), Some(&4));
733 /// assert_eq!(iterator.next(), None);
735 #[stable(feature = "rust1", since = "1.0.0")]
737 pub fn iter(&self) -> Iter<'_, T> {
741 /// Returns an iterator that allows modifying each value.
746 /// let x = &mut [1, 2, 4];
747 /// for elem in x.iter_mut() {
750 /// assert_eq!(x, &[3, 4, 6]);
752 #[stable(feature = "rust1", since = "1.0.0")]
754 pub fn iter_mut(&mut self) -> IterMut<'_, T> {
758 /// Returns an iterator over all contiguous windows of length
759 /// `size`. The windows overlap. If the slice is shorter than
760 /// `size`, the iterator returns no values.
764 /// Panics if `size` is 0.
769 /// let slice = ['r', 'u', 's', 't'];
770 /// let mut iter = slice.windows(2);
771 /// assert_eq!(iter.next().unwrap(), &['r', 'u']);
772 /// assert_eq!(iter.next().unwrap(), &['u', 's']);
773 /// assert_eq!(iter.next().unwrap(), &['s', 't']);
774 /// assert!(iter.next().is_none());
777 /// If the slice is shorter than `size`:
780 /// let slice = ['f', 'o', 'o'];
781 /// let mut iter = slice.windows(4);
782 /// assert!(iter.next().is_none());
784 #[stable(feature = "rust1", since = "1.0.0")]
786 pub fn windows(&self, size: usize) -> Windows<'_, T> {
787 let size = NonZeroUsize::new(size).expect("size is zero");
788 Windows::new(self, size)
791 /// Returns an iterator over `chunk_size` elements of the slice at a time, starting at the
792 /// beginning of the slice.
794 /// The chunks are slices and do not overlap. If `chunk_size` does not divide the length of the
795 /// slice, then the last chunk will not have length `chunk_size`.
797 /// See [`chunks_exact`] for a variant of this iterator that returns chunks of always exactly
798 /// `chunk_size` elements, and [`rchunks`] for the same iterator but starting at the end of the
803 /// Panics if `chunk_size` is 0.
808 /// let slice = ['l', 'o', 'r', 'e', 'm'];
809 /// let mut iter = slice.chunks(2);
810 /// assert_eq!(iter.next().unwrap(), &['l', 'o']);
811 /// assert_eq!(iter.next().unwrap(), &['r', 'e']);
812 /// assert_eq!(iter.next().unwrap(), &['m']);
813 /// assert!(iter.next().is_none());
816 /// [`chunks_exact`]: slice::chunks_exact
817 /// [`rchunks`]: slice::rchunks
818 #[stable(feature = "rust1", since = "1.0.0")]
820 pub fn chunks(&self, chunk_size: usize) -> Chunks<'_, T> {
821 assert_ne!(chunk_size, 0);
822 Chunks::new(self, chunk_size)
825 /// Returns an iterator over `chunk_size` elements of the slice at a time, starting at the
826 /// beginning of the slice.
828 /// The chunks are mutable slices, and do not overlap. If `chunk_size` does not divide the
829 /// length of the slice, then the last chunk will not have length `chunk_size`.
831 /// See [`chunks_exact_mut`] for a variant of this iterator that returns chunks of always
832 /// exactly `chunk_size` elements, and [`rchunks_mut`] for the same iterator but starting at
833 /// the end of the slice.
837 /// Panics if `chunk_size` is 0.
842 /// let v = &mut [0, 0, 0, 0, 0];
843 /// let mut count = 1;
845 /// for chunk in v.chunks_mut(2) {
846 /// for elem in chunk.iter_mut() {
851 /// assert_eq!(v, &[1, 1, 2, 2, 3]);
854 /// [`chunks_exact_mut`]: slice::chunks_exact_mut
855 /// [`rchunks_mut`]: slice::rchunks_mut
856 #[stable(feature = "rust1", since = "1.0.0")]
858 pub fn chunks_mut(&mut self, chunk_size: usize) -> ChunksMut<'_, T> {
859 assert_ne!(chunk_size, 0);
860 ChunksMut::new(self, chunk_size)
863 /// Returns an iterator over `chunk_size` elements of the slice at a time, starting at the
864 /// beginning of the slice.
866 /// The chunks are slices and do not overlap. If `chunk_size` does not divide the length of the
867 /// slice, then the last up to `chunk_size-1` elements will be omitted and can be retrieved
868 /// from the `remainder` function of the iterator.
870 /// Due to each chunk having exactly `chunk_size` elements, the compiler can often optimize the
871 /// resulting code better than in the case of [`chunks`].
873 /// See [`chunks`] for a variant of this iterator that also returns the remainder as a smaller
874 /// chunk, and [`rchunks_exact`] for the same iterator but starting at the end of the slice.
878 /// Panics if `chunk_size` is 0.
883 /// let slice = ['l', 'o', 'r', 'e', 'm'];
884 /// let mut iter = slice.chunks_exact(2);
885 /// assert_eq!(iter.next().unwrap(), &['l', 'o']);
886 /// assert_eq!(iter.next().unwrap(), &['r', 'e']);
887 /// assert!(iter.next().is_none());
888 /// assert_eq!(iter.remainder(), &['m']);
891 /// [`chunks`]: slice::chunks
892 /// [`rchunks_exact`]: slice::rchunks_exact
893 #[stable(feature = "chunks_exact", since = "1.31.0")]
895 pub fn chunks_exact(&self, chunk_size: usize) -> ChunksExact<'_, T> {
896 assert_ne!(chunk_size, 0);
897 ChunksExact::new(self, chunk_size)
900 /// Returns an iterator over `chunk_size` elements of the slice at a time, starting at the
901 /// beginning of the slice.
903 /// The chunks are mutable slices, and do not overlap. If `chunk_size` does not divide the
904 /// length of the slice, then the last up to `chunk_size-1` elements will be omitted and can be
905 /// retrieved from the `into_remainder` function of the iterator.
907 /// Due to each chunk having exactly `chunk_size` elements, the compiler can often optimize the
908 /// resulting code better than in the case of [`chunks_mut`].
910 /// See [`chunks_mut`] for a variant of this iterator that also returns the remainder as a
911 /// smaller chunk, and [`rchunks_exact_mut`] for the same iterator but starting at the end of
916 /// Panics if `chunk_size` is 0.
921 /// let v = &mut [0, 0, 0, 0, 0];
922 /// let mut count = 1;
924 /// for chunk in v.chunks_exact_mut(2) {
925 /// for elem in chunk.iter_mut() {
930 /// assert_eq!(v, &[1, 1, 2, 2, 0]);
933 /// [`chunks_mut`]: slice::chunks_mut
934 /// [`rchunks_exact_mut`]: slice::rchunks_exact_mut
935 #[stable(feature = "chunks_exact", since = "1.31.0")]
937 pub fn chunks_exact_mut(&mut self, chunk_size: usize) -> ChunksExactMut<'_, T> {
938 assert_ne!(chunk_size, 0);
939 ChunksExactMut::new(self, chunk_size)
942 /// Splits the slice into a slice of `N`-element arrays,
943 /// assuming that there's no remainder.
947 /// This may only be called when
948 /// - The slice splits exactly into `N`-element chunks (aka `self.len() % N == 0`).
954 /// #![feature(slice_as_chunks)]
955 /// let slice: &[char] = &['l', 'o', 'r', 'e', 'm', '!'];
956 /// let chunks: &[[char; 1]] =
957 /// // SAFETY: 1-element chunks never have remainder
958 /// unsafe { slice.as_chunks_unchecked() };
959 /// assert_eq!(chunks, &[['l'], ['o'], ['r'], ['e'], ['m'], ['!']]);
960 /// let chunks: &[[char; 3]] =
961 /// // SAFETY: The slice length (6) is a multiple of 3
962 /// unsafe { slice.as_chunks_unchecked() };
963 /// assert_eq!(chunks, &[['l', 'o', 'r'], ['e', 'm', '!']]);
965 /// // These would be unsound:
966 /// // let chunks: &[[_; 5]] = slice.as_chunks_unchecked() // The slice length is not a multiple of 5
967 /// // let chunks: &[[_; 0]] = slice.as_chunks_unchecked() // Zero-length chunks are never allowed
969 #[unstable(feature = "slice_as_chunks", issue = "74985")]
972 pub unsafe fn as_chunks_unchecked<const N: usize>(&self) -> &[[T; N]] {
973 debug_assert_ne!(N, 0);
974 debug_assert_eq!(self.len() % N, 0);
976 // SAFETY: Our precondition is exactly what's needed to call this
977 unsafe { crate::intrinsics::exact_div(self.len(), N) };
978 // SAFETY: We cast a slice of `new_len * N` elements into
979 // a slice of `new_len` many `N` elements chunks.
980 unsafe { from_raw_parts(self.as_ptr().cast(), new_len) }
983 /// Splits the slice into a slice of `N`-element arrays,
984 /// starting at the beginning of the slice,
985 /// and a remainder slice with length strictly less than `N`.
989 /// Panics if `N` is 0. This check will most probably get changed to a compile time
990 /// error before this method gets stabilized.
995 /// #![feature(slice_as_chunks)]
996 /// let slice = ['l', 'o', 'r', 'e', 'm'];
997 /// let (chunks, remainder) = slice.as_chunks();
998 /// assert_eq!(chunks, &[['l', 'o'], ['r', 'e']]);
999 /// assert_eq!(remainder, &['m']);
1001 #[unstable(feature = "slice_as_chunks", issue = "74985")]
1004 pub fn as_chunks<const N: usize>(&self) -> (&[[T; N]], &[T]) {
1006 let len = self.len() / N;
1007 let (multiple_of_n, remainder) = self.split_at(len * N);
1008 // SAFETY: We already panicked for zero, and ensured by construction
1009 // that the length of the subslice is a multiple of N.
1010 let array_slice = unsafe { multiple_of_n.as_chunks_unchecked() };
1011 (array_slice, remainder)
1014 /// Splits the slice into a slice of `N`-element arrays,
1015 /// starting at the end of the slice,
1016 /// and a remainder slice with length strictly less than `N`.
1020 /// Panics if `N` is 0. This check will most probably get changed to a compile time
1021 /// error before this method gets stabilized.
1026 /// #![feature(slice_as_chunks)]
1027 /// let slice = ['l', 'o', 'r', 'e', 'm'];
1028 /// let (remainder, chunks) = slice.as_rchunks();
1029 /// assert_eq!(remainder, &['l']);
1030 /// assert_eq!(chunks, &[['o', 'r'], ['e', 'm']]);
1032 #[unstable(feature = "slice_as_chunks", issue = "74985")]
1035 pub fn as_rchunks<const N: usize>(&self) -> (&[T], &[[T; N]]) {
1037 let len = self.len() / N;
1038 let (remainder, multiple_of_n) = self.split_at(self.len() - len * N);
1039 // SAFETY: We already panicked for zero, and ensured by construction
1040 // that the length of the subslice is a multiple of N.
1041 let array_slice = unsafe { multiple_of_n.as_chunks_unchecked() };
1042 (remainder, array_slice)
1045 /// Returns an iterator over `N` elements of the slice at a time, starting at the
1046 /// beginning of the slice.
1048 /// The chunks are array references and do not overlap. If `N` does not divide the
1049 /// length of the slice, then the last up to `N-1` elements will be omitted and can be
1050 /// retrieved from the `remainder` function of the iterator.
1052 /// This method is the const generic equivalent of [`chunks_exact`].
1056 /// Panics if `N` is 0. This check will most probably get changed to a compile time
1057 /// error before this method gets stabilized.
1062 /// #![feature(array_chunks)]
1063 /// let slice = ['l', 'o', 'r', 'e', 'm'];
1064 /// let mut iter = slice.array_chunks();
1065 /// assert_eq!(iter.next().unwrap(), &['l', 'o']);
1066 /// assert_eq!(iter.next().unwrap(), &['r', 'e']);
1067 /// assert!(iter.next().is_none());
1068 /// assert_eq!(iter.remainder(), &['m']);
1071 /// [`chunks_exact`]: slice::chunks_exact
1072 #[unstable(feature = "array_chunks", issue = "74985")]
1074 pub fn array_chunks<const N: usize>(&self) -> ArrayChunks<'_, T, N> {
1076 ArrayChunks::new(self)
1079 /// Splits the slice into a slice of `N`-element arrays,
1080 /// assuming that there's no remainder.
1084 /// This may only be called when
1085 /// - The slice splits exactly into `N`-element chunks (aka `self.len() % N == 0`).
1091 /// #![feature(slice_as_chunks)]
1092 /// let slice: &mut [char] = &mut ['l', 'o', 'r', 'e', 'm', '!'];
1093 /// let chunks: &mut [[char; 1]] =
1094 /// // SAFETY: 1-element chunks never have remainder
1095 /// unsafe { slice.as_chunks_unchecked_mut() };
1096 /// chunks[0] = ['L'];
1097 /// assert_eq!(chunks, &[['L'], ['o'], ['r'], ['e'], ['m'], ['!']]);
1098 /// let chunks: &mut [[char; 3]] =
1099 /// // SAFETY: The slice length (6) is a multiple of 3
1100 /// unsafe { slice.as_chunks_unchecked_mut() };
1101 /// chunks[1] = ['a', 'x', '?'];
1102 /// assert_eq!(slice, &['L', 'o', 'r', 'a', 'x', '?']);
1104 /// // These would be unsound:
1105 /// // let chunks: &[[_; 5]] = slice.as_chunks_unchecked_mut() // The slice length is not a multiple of 5
1106 /// // let chunks: &[[_; 0]] = slice.as_chunks_unchecked_mut() // Zero-length chunks are never allowed
1108 #[unstable(feature = "slice_as_chunks", issue = "74985")]
1111 pub unsafe fn as_chunks_unchecked_mut<const N: usize>(&mut self) -> &mut [[T; N]] {
1112 debug_assert_ne!(N, 0);
1113 debug_assert_eq!(self.len() % N, 0);
1115 // SAFETY: Our precondition is exactly what's needed to call this
1116 unsafe { crate::intrinsics::exact_div(self.len(), N) };
1117 // SAFETY: We cast a slice of `new_len * N` elements into
1118 // a slice of `new_len` many `N` elements chunks.
1119 unsafe { from_raw_parts_mut(self.as_mut_ptr().cast(), new_len) }
1122 /// Splits the slice into a slice of `N`-element arrays,
1123 /// starting at the beginning of the slice,
1124 /// and a remainder slice with length strictly less than `N`.
1128 /// Panics if `N` is 0. This check will most probably get changed to a compile time
1129 /// error before this method gets stabilized.
1134 /// #![feature(slice_as_chunks)]
1135 /// let v = &mut [0, 0, 0, 0, 0];
1136 /// let mut count = 1;
1138 /// let (chunks, remainder) = v.as_chunks_mut();
1139 /// remainder[0] = 9;
1140 /// for chunk in chunks {
1141 /// *chunk = [count; 2];
1144 /// assert_eq!(v, &[1, 1, 2, 2, 9]);
1146 #[unstable(feature = "slice_as_chunks", issue = "74985")]
1149 pub fn as_chunks_mut<const N: usize>(&mut self) -> (&mut [[T; N]], &mut [T]) {
1151 let len = self.len() / N;
1152 let (multiple_of_n, remainder) = self.split_at_mut(len * N);
1153 // SAFETY: We already panicked for zero, and ensured by construction
1154 // that the length of the subslice is a multiple of N.
1155 let array_slice = unsafe { multiple_of_n.as_chunks_unchecked_mut() };
1156 (array_slice, remainder)
1159 /// Splits the slice into a slice of `N`-element arrays,
1160 /// starting at the end of the slice,
1161 /// and a remainder slice with length strictly less than `N`.
1165 /// Panics if `N` is 0. This check will most probably get changed to a compile time
1166 /// error before this method gets stabilized.
1171 /// #![feature(slice_as_chunks)]
1172 /// let v = &mut [0, 0, 0, 0, 0];
1173 /// let mut count = 1;
1175 /// let (remainder, chunks) = v.as_rchunks_mut();
1176 /// remainder[0] = 9;
1177 /// for chunk in chunks {
1178 /// *chunk = [count; 2];
1181 /// assert_eq!(v, &[9, 1, 1, 2, 2]);
1183 #[unstable(feature = "slice_as_chunks", issue = "74985")]
1186 pub fn as_rchunks_mut<const N: usize>(&mut self) -> (&mut [T], &mut [[T; N]]) {
1188 let len = self.len() / N;
1189 let (remainder, multiple_of_n) = self.split_at_mut(self.len() - len * N);
1190 // SAFETY: We already panicked for zero, and ensured by construction
1191 // that the length of the subslice is a multiple of N.
1192 let array_slice = unsafe { multiple_of_n.as_chunks_unchecked_mut() };
1193 (remainder, array_slice)
1196 /// Returns an iterator over `N` elements of the slice at a time, starting at the
1197 /// beginning of the slice.
1199 /// The chunks are mutable array references and do not overlap. If `N` does not divide
1200 /// the length of the slice, then the last up to `N-1` elements will be omitted and
1201 /// can be retrieved from the `into_remainder` function of the iterator.
1203 /// This method is the const generic equivalent of [`chunks_exact_mut`].
1207 /// Panics if `N` is 0. This check will most probably get changed to a compile time
1208 /// error before this method gets stabilized.
1213 /// #![feature(array_chunks)]
1214 /// let v = &mut [0, 0, 0, 0, 0];
1215 /// let mut count = 1;
1217 /// for chunk in v.array_chunks_mut() {
1218 /// *chunk = [count; 2];
1221 /// assert_eq!(v, &[1, 1, 2, 2, 0]);
1224 /// [`chunks_exact_mut`]: slice::chunks_exact_mut
1225 #[unstable(feature = "array_chunks", issue = "74985")]
1227 pub fn array_chunks_mut<const N: usize>(&mut self) -> ArrayChunksMut<'_, T, N> {
1229 ArrayChunksMut::new(self)
1232 /// Returns an iterator over overlapping windows of `N` elements of a slice,
1233 /// starting at the beginning of the slice.
1235 /// This is the const generic equivalent of [`windows`].
1237 /// If `N` is greater than the size of the slice, it will return no windows.
1241 /// Panics if `N` is 0. This check will most probably get changed to a compile time
1242 /// error before this method gets stabilized.
1247 /// #![feature(array_windows)]
1248 /// let slice = [0, 1, 2, 3];
1249 /// let mut iter = slice.array_windows();
1250 /// assert_eq!(iter.next().unwrap(), &[0, 1]);
1251 /// assert_eq!(iter.next().unwrap(), &[1, 2]);
1252 /// assert_eq!(iter.next().unwrap(), &[2, 3]);
1253 /// assert!(iter.next().is_none());
1256 /// [`windows`]: slice::windows
1257 #[unstable(feature = "array_windows", issue = "75027")]
1259 pub fn array_windows<const N: usize>(&self) -> ArrayWindows<'_, T, N> {
1261 ArrayWindows::new(self)
1264 /// Returns an iterator over `chunk_size` elements of the slice at a time, starting at the end
1267 /// The chunks are slices and do not overlap. If `chunk_size` does not divide the length of the
1268 /// slice, then the last chunk will not have length `chunk_size`.
1270 /// See [`rchunks_exact`] for a variant of this iterator that returns chunks of always exactly
1271 /// `chunk_size` elements, and [`chunks`] for the same iterator but starting at the beginning
1276 /// Panics if `chunk_size` is 0.
1281 /// let slice = ['l', 'o', 'r', 'e', 'm'];
1282 /// let mut iter = slice.rchunks(2);
1283 /// assert_eq!(iter.next().unwrap(), &['e', 'm']);
1284 /// assert_eq!(iter.next().unwrap(), &['o', 'r']);
1285 /// assert_eq!(iter.next().unwrap(), &['l']);
1286 /// assert!(iter.next().is_none());
1289 /// [`rchunks_exact`]: slice::rchunks_exact
1290 /// [`chunks`]: slice::chunks
1291 #[stable(feature = "rchunks", since = "1.31.0")]
1293 pub fn rchunks(&self, chunk_size: usize) -> RChunks<'_, T> {
1294 assert!(chunk_size != 0);
1295 RChunks::new(self, chunk_size)
1298 /// Returns an iterator over `chunk_size` elements of the slice at a time, starting at the end
1301 /// The chunks are mutable slices, and do not overlap. If `chunk_size` does not divide the
1302 /// length of the slice, then the last chunk will not have length `chunk_size`.
1304 /// See [`rchunks_exact_mut`] for a variant of this iterator that returns chunks of always
1305 /// exactly `chunk_size` elements, and [`chunks_mut`] for the same iterator but starting at the
1306 /// beginning of the slice.
1310 /// Panics if `chunk_size` is 0.
1315 /// let v = &mut [0, 0, 0, 0, 0];
1316 /// let mut count = 1;
1318 /// for chunk in v.rchunks_mut(2) {
1319 /// for elem in chunk.iter_mut() {
1324 /// assert_eq!(v, &[3, 2, 2, 1, 1]);
1327 /// [`rchunks_exact_mut`]: slice::rchunks_exact_mut
1328 /// [`chunks_mut`]: slice::chunks_mut
1329 #[stable(feature = "rchunks", since = "1.31.0")]
1331 pub fn rchunks_mut(&mut self, chunk_size: usize) -> RChunksMut<'_, T> {
1332 assert!(chunk_size != 0);
1333 RChunksMut::new(self, chunk_size)
1336 /// Returns an iterator over `chunk_size` elements of the slice at a time, starting at the
1337 /// end of the slice.
1339 /// The chunks are slices and do not overlap. If `chunk_size` does not divide the length of the
1340 /// slice, then the last up to `chunk_size-1` elements will be omitted and can be retrieved
1341 /// from the `remainder` function of the iterator.
1343 /// Due to each chunk having exactly `chunk_size` elements, the compiler can often optimize the
1344 /// resulting code better than in the case of [`chunks`].
1346 /// See [`rchunks`] for a variant of this iterator that also returns the remainder as a smaller
1347 /// chunk, and [`chunks_exact`] for the same iterator but starting at the beginning of the
1352 /// Panics if `chunk_size` is 0.
1357 /// let slice = ['l', 'o', 'r', 'e', 'm'];
1358 /// let mut iter = slice.rchunks_exact(2);
1359 /// assert_eq!(iter.next().unwrap(), &['e', 'm']);
1360 /// assert_eq!(iter.next().unwrap(), &['o', 'r']);
1361 /// assert!(iter.next().is_none());
1362 /// assert_eq!(iter.remainder(), &['l']);
1365 /// [`chunks`]: slice::chunks
1366 /// [`rchunks`]: slice::rchunks
1367 /// [`chunks_exact`]: slice::chunks_exact
1368 #[stable(feature = "rchunks", since = "1.31.0")]
1370 pub fn rchunks_exact(&self, chunk_size: usize) -> RChunksExact<'_, T> {
1371 assert!(chunk_size != 0);
1372 RChunksExact::new(self, chunk_size)
1375 /// Returns an iterator over `chunk_size` elements of the slice at a time, starting at the end
1378 /// The chunks are mutable slices, and do not overlap. If `chunk_size` does not divide the
1379 /// length of the slice, then the last up to `chunk_size-1` elements will be omitted and can be
1380 /// retrieved from the `into_remainder` function of the iterator.
1382 /// Due to each chunk having exactly `chunk_size` elements, the compiler can often optimize the
1383 /// resulting code better than in the case of [`chunks_mut`].
1385 /// See [`rchunks_mut`] for a variant of this iterator that also returns the remainder as a
1386 /// smaller chunk, and [`chunks_exact_mut`] for the same iterator but starting at the beginning
1391 /// Panics if `chunk_size` is 0.
1396 /// let v = &mut [0, 0, 0, 0, 0];
1397 /// let mut count = 1;
1399 /// for chunk in v.rchunks_exact_mut(2) {
1400 /// for elem in chunk.iter_mut() {
1405 /// assert_eq!(v, &[0, 2, 2, 1, 1]);
1408 /// [`chunks_mut`]: slice::chunks_mut
1409 /// [`rchunks_mut`]: slice::rchunks_mut
1410 /// [`chunks_exact_mut`]: slice::chunks_exact_mut
1411 #[stable(feature = "rchunks", since = "1.31.0")]
1413 pub fn rchunks_exact_mut(&mut self, chunk_size: usize) -> RChunksExactMut<'_, T> {
1414 assert!(chunk_size != 0);
1415 RChunksExactMut::new(self, chunk_size)
1418 /// Returns an iterator over the slice producing non-overlapping runs
1419 /// of elements using the predicate to separate them.
1421 /// The predicate is called on two elements following themselves,
1422 /// it means the predicate is called on `slice[0]` and `slice[1]`
1423 /// then on `slice[1]` and `slice[2]` and so on.
1428 /// #![feature(slice_group_by)]
1430 /// let slice = &[1, 1, 1, 3, 3, 2, 2, 2];
1432 /// let mut iter = slice.group_by(|a, b| a == b);
1434 /// assert_eq!(iter.next(), Some(&[1, 1, 1][..]));
1435 /// assert_eq!(iter.next(), Some(&[3, 3][..]));
1436 /// assert_eq!(iter.next(), Some(&[2, 2, 2][..]));
1437 /// assert_eq!(iter.next(), None);
1440 /// This method can be used to extract the sorted subslices:
1443 /// #![feature(slice_group_by)]
1445 /// let slice = &[1, 1, 2, 3, 2, 3, 2, 3, 4];
1447 /// let mut iter = slice.group_by(|a, b| a <= b);
1449 /// assert_eq!(iter.next(), Some(&[1, 1, 2, 3][..]));
1450 /// assert_eq!(iter.next(), Some(&[2, 3][..]));
1451 /// assert_eq!(iter.next(), Some(&[2, 3, 4][..]));
1452 /// assert_eq!(iter.next(), None);
1454 #[unstable(feature = "slice_group_by", issue = "80552")]
1456 pub fn group_by<F>(&self, pred: F) -> GroupBy<'_, T, F>
1458 F: FnMut(&T, &T) -> bool,
1460 GroupBy::new(self, pred)
1463 /// Returns an iterator over the slice producing non-overlapping mutable
1464 /// runs of elements using the predicate to separate them.
1466 /// The predicate is called on two elements following themselves,
1467 /// it means the predicate is called on `slice[0]` and `slice[1]`
1468 /// then on `slice[1]` and `slice[2]` and so on.
1473 /// #![feature(slice_group_by)]
1475 /// let slice = &mut [1, 1, 1, 3, 3, 2, 2, 2];
1477 /// let mut iter = slice.group_by_mut(|a, b| a == b);
1479 /// assert_eq!(iter.next(), Some(&mut [1, 1, 1][..]));
1480 /// assert_eq!(iter.next(), Some(&mut [3, 3][..]));
1481 /// assert_eq!(iter.next(), Some(&mut [2, 2, 2][..]));
1482 /// assert_eq!(iter.next(), None);
1485 /// This method can be used to extract the sorted subslices:
1488 /// #![feature(slice_group_by)]
1490 /// let slice = &mut [1, 1, 2, 3, 2, 3, 2, 3, 4];
1492 /// let mut iter = slice.group_by_mut(|a, b| a <= b);
1494 /// assert_eq!(iter.next(), Some(&mut [1, 1, 2, 3][..]));
1495 /// assert_eq!(iter.next(), Some(&mut [2, 3][..]));
1496 /// assert_eq!(iter.next(), Some(&mut [2, 3, 4][..]));
1497 /// assert_eq!(iter.next(), None);
1499 #[unstable(feature = "slice_group_by", issue = "80552")]
1501 pub fn group_by_mut<F>(&mut self, pred: F) -> GroupByMut<'_, T, F>
1503 F: FnMut(&T, &T) -> bool,
1505 GroupByMut::new(self, pred)
1508 /// Divides one slice into two at an index.
1510 /// The first will contain all indices from `[0, mid)` (excluding
1511 /// the index `mid` itself) and the second will contain all
1512 /// indices from `[mid, len)` (excluding the index `len` itself).
1516 /// Panics if `mid > len`.
1521 /// let v = [1, 2, 3, 4, 5, 6];
1524 /// let (left, right) = v.split_at(0);
1525 /// assert_eq!(left, []);
1526 /// assert_eq!(right, [1, 2, 3, 4, 5, 6]);
1530 /// let (left, right) = v.split_at(2);
1531 /// assert_eq!(left, [1, 2]);
1532 /// assert_eq!(right, [3, 4, 5, 6]);
1536 /// let (left, right) = v.split_at(6);
1537 /// assert_eq!(left, [1, 2, 3, 4, 5, 6]);
1538 /// assert_eq!(right, []);
1541 #[stable(feature = "rust1", since = "1.0.0")]
1545 pub fn split_at(&self, mid: usize) -> (&[T], &[T]) {
1546 assert!(mid <= self.len());
1547 // SAFETY: `[ptr; mid]` and `[mid; len]` are inside `self`, which
1548 // fulfills the requirements of `from_raw_parts_mut`.
1549 unsafe { self.split_at_unchecked(mid) }
1552 /// Divides one mutable slice into two at an index.
1554 /// The first will contain all indices from `[0, mid)` (excluding
1555 /// the index `mid` itself) and the second will contain all
1556 /// indices from `[mid, len)` (excluding the index `len` itself).
1560 /// Panics if `mid > len`.
1565 /// let mut v = [1, 0, 3, 0, 5, 6];
1566 /// let (left, right) = v.split_at_mut(2);
1567 /// assert_eq!(left, [1, 0]);
1568 /// assert_eq!(right, [3, 0, 5, 6]);
1571 /// assert_eq!(v, [1, 2, 3, 4, 5, 6]);
1573 #[stable(feature = "rust1", since = "1.0.0")]
1577 pub fn split_at_mut(&mut self, mid: usize) -> (&mut [T], &mut [T]) {
1578 assert!(mid <= self.len());
1579 // SAFETY: `[ptr; mid]` and `[mid; len]` are inside `self`, which
1580 // fulfills the requirements of `from_raw_parts_mut`.
1581 unsafe { self.split_at_mut_unchecked(mid) }
1584 /// Divides one slice into two at an index, without doing bounds checking.
1586 /// The first will contain all indices from `[0, mid)` (excluding
1587 /// the index `mid` itself) and the second will contain all
1588 /// indices from `[mid, len)` (excluding the index `len` itself).
1590 /// For a safe alternative see [`split_at`].
1594 /// Calling this method with an out-of-bounds index is *[undefined behavior]*
1595 /// even if the resulting reference is not used. The caller has to ensure that
1596 /// `0 <= mid <= self.len()`.
1598 /// [`split_at`]: slice::split_at
1599 /// [undefined behavior]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
1604 /// #![feature(slice_split_at_unchecked)]
1606 /// let v = [1, 2, 3, 4, 5, 6];
1609 /// let (left, right) = v.split_at_unchecked(0);
1610 /// assert_eq!(left, []);
1611 /// assert_eq!(right, [1, 2, 3, 4, 5, 6]);
1615 /// let (left, right) = v.split_at_unchecked(2);
1616 /// assert_eq!(left, [1, 2]);
1617 /// assert_eq!(right, [3, 4, 5, 6]);
1621 /// let (left, right) = v.split_at_unchecked(6);
1622 /// assert_eq!(left, [1, 2, 3, 4, 5, 6]);
1623 /// assert_eq!(right, []);
1626 #[unstable(feature = "slice_split_at_unchecked", reason = "new API", issue = "76014")]
1629 pub unsafe fn split_at_unchecked(&self, mid: usize) -> (&[T], &[T]) {
1630 // SAFETY: Caller has to check that `0 <= mid <= self.len()`
1631 unsafe { (self.get_unchecked(..mid), self.get_unchecked(mid..)) }
1634 /// Divides one mutable slice into two at an index, without doing bounds checking.
1636 /// The first will contain all indices from `[0, mid)` (excluding
1637 /// the index `mid` itself) and the second will contain all
1638 /// indices from `[mid, len)` (excluding the index `len` itself).
1640 /// For a safe alternative see [`split_at_mut`].
1644 /// Calling this method with an out-of-bounds index is *[undefined behavior]*
1645 /// even if the resulting reference is not used. The caller has to ensure that
1646 /// `0 <= mid <= self.len()`.
1648 /// [`split_at_mut`]: slice::split_at_mut
1649 /// [undefined behavior]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
1654 /// #![feature(slice_split_at_unchecked)]
1656 /// let mut v = [1, 0, 3, 0, 5, 6];
1657 /// // scoped to restrict the lifetime of the borrows
1659 /// let (left, right) = v.split_at_mut_unchecked(2);
1660 /// assert_eq!(left, [1, 0]);
1661 /// assert_eq!(right, [3, 0, 5, 6]);
1665 /// assert_eq!(v, [1, 2, 3, 4, 5, 6]);
1667 #[unstable(feature = "slice_split_at_unchecked", reason = "new API", issue = "76014")]
1670 pub unsafe fn split_at_mut_unchecked(&mut self, mid: usize) -> (&mut [T], &mut [T]) {
1671 let len = self.len();
1672 let ptr = self.as_mut_ptr();
1674 // SAFETY: Caller has to check that `0 <= mid <= self.len()`.
1676 // `[ptr; mid]` and `[mid; len]` are not overlapping, so returning a mutable reference
1678 unsafe { (from_raw_parts_mut(ptr, mid), from_raw_parts_mut(ptr.add(mid), len - mid)) }
1681 /// Divides one slice into an array and a remainder slice at an index.
1683 /// The array will contain all indices from `[0, N)` (excluding
1684 /// the index `N` itself) and the slice will contain all
1685 /// indices from `[N, len)` (excluding the index `len` itself).
1689 /// Panics if `N > len`.
1694 /// #![feature(split_array)]
1696 /// let v = &[1, 2, 3, 4, 5, 6][..];
1699 /// let (left, right) = v.split_array_ref::<0>();
1700 /// assert_eq!(left, &[]);
1701 /// assert_eq!(right, [1, 2, 3, 4, 5, 6]);
1705 /// let (left, right) = v.split_array_ref::<2>();
1706 /// assert_eq!(left, &[1, 2]);
1707 /// assert_eq!(right, [3, 4, 5, 6]);
1711 /// let (left, right) = v.split_array_ref::<6>();
1712 /// assert_eq!(left, &[1, 2, 3, 4, 5, 6]);
1713 /// assert_eq!(right, []);
1716 #[unstable(feature = "split_array", reason = "new API", issue = "90091")]
1720 pub fn split_array_ref<const N: usize>(&self) -> (&[T; N], &[T]) {
1721 let (a, b) = self.split_at(N);
1722 // SAFETY: a points to [T; N]? Yes it's [T] of length N (checked by split_at)
1723 unsafe { (&*(a.as_ptr() as *const [T; N]), b) }
1726 /// Divides one mutable slice into an array and a remainder slice at an index.
1728 /// The array will contain all indices from `[0, N)` (excluding
1729 /// the index `N` itself) and the slice will contain all
1730 /// indices from `[N, len)` (excluding the index `len` itself).
1734 /// Panics if `N > len`.
1739 /// #![feature(split_array)]
1741 /// let mut v = &mut [1, 0, 3, 0, 5, 6][..];
1742 /// let (left, right) = v.split_array_mut::<2>();
1743 /// assert_eq!(left, &mut [1, 0]);
1744 /// assert_eq!(right, [3, 0, 5, 6]);
1747 /// assert_eq!(v, [1, 2, 3, 4, 5, 6]);
1749 #[unstable(feature = "split_array", reason = "new API", issue = "90091")]
1753 pub fn split_array_mut<const N: usize>(&mut self) -> (&mut [T; N], &mut [T]) {
1754 let (a, b) = self.split_at_mut(N);
1755 // SAFETY: a points to [T; N]? Yes it's [T] of length N (checked by split_at_mut)
1756 unsafe { (&mut *(a.as_mut_ptr() as *mut [T; N]), b) }
1759 /// Divides one slice into an array and a remainder slice at an index from
1762 /// The slice will contain all indices from `[0, len - N)` (excluding
1763 /// the index `len - N` itself) and the array will contain all
1764 /// indices from `[len - N, len)` (excluding the index `len` itself).
1768 /// Panics if `N > len`.
1773 /// #![feature(split_array)]
1775 /// let v = &[1, 2, 3, 4, 5, 6][..];
1778 /// let (left, right) = v.rsplit_array_ref::<0>();
1779 /// assert_eq!(left, [1, 2, 3, 4, 5, 6]);
1780 /// assert_eq!(right, &[]);
1784 /// let (left, right) = v.rsplit_array_ref::<2>();
1785 /// assert_eq!(left, [1, 2, 3, 4]);
1786 /// assert_eq!(right, &[5, 6]);
1790 /// let (left, right) = v.rsplit_array_ref::<6>();
1791 /// assert_eq!(left, []);
1792 /// assert_eq!(right, &[1, 2, 3, 4, 5, 6]);
1795 #[unstable(feature = "split_array", reason = "new API", issue = "90091")]
1798 pub fn rsplit_array_ref<const N: usize>(&self) -> (&[T], &[T; N]) {
1799 assert!(N <= self.len());
1800 let (a, b) = self.split_at(self.len() - N);
1801 // SAFETY: b points to [T; N]? Yes it's [T] of length N (checked by split_at)
1802 unsafe { (a, &*(b.as_ptr() as *const [T; N])) }
1805 /// Divides one mutable slice into an array and a remainder slice at an
1806 /// index from the end.
1808 /// The slice will contain all indices from `[0, len - N)` (excluding
1809 /// the index `N` itself) and the array will contain all
1810 /// indices from `[len - N, len)` (excluding the index `len` itself).
1814 /// Panics if `N > len`.
1819 /// #![feature(split_array)]
1821 /// let mut v = &mut [1, 0, 3, 0, 5, 6][..];
1822 /// let (left, right) = v.rsplit_array_mut::<4>();
1823 /// assert_eq!(left, [1, 0]);
1824 /// assert_eq!(right, &mut [3, 0, 5, 6]);
1827 /// assert_eq!(v, [1, 2, 3, 4, 5, 6]);
1829 #[unstable(feature = "split_array", reason = "new API", issue = "90091")]
1832 pub fn rsplit_array_mut<const N: usize>(&mut self) -> (&mut [T], &mut [T; N]) {
1833 assert!(N <= self.len());
1834 let (a, b) = self.split_at_mut(self.len() - N);
1835 // SAFETY: b points to [T; N]? Yes it's [T] of length N (checked by split_at_mut)
1836 unsafe { (a, &mut *(b.as_mut_ptr() as *mut [T; N])) }
1839 /// Returns an iterator over subslices separated by elements that match
1840 /// `pred`. The matched element is not contained in the subslices.
1845 /// let slice = [10, 40, 33, 20];
1846 /// let mut iter = slice.split(|num| num % 3 == 0);
1848 /// assert_eq!(iter.next().unwrap(), &[10, 40]);
1849 /// assert_eq!(iter.next().unwrap(), &[20]);
1850 /// assert!(iter.next().is_none());
1853 /// If the first element is matched, an empty slice will be the first item
1854 /// returned by the iterator. Similarly, if the last element in the slice
1855 /// is matched, an empty slice will be the last item returned by the
1859 /// let slice = [10, 40, 33];
1860 /// let mut iter = slice.split(|num| num % 3 == 0);
1862 /// assert_eq!(iter.next().unwrap(), &[10, 40]);
1863 /// assert_eq!(iter.next().unwrap(), &[]);
1864 /// assert!(iter.next().is_none());
1867 /// If two matched elements are directly adjacent, an empty slice will be
1868 /// present between them:
1871 /// let slice = [10, 6, 33, 20];
1872 /// let mut iter = slice.split(|num| num % 3 == 0);
1874 /// assert_eq!(iter.next().unwrap(), &[10]);
1875 /// assert_eq!(iter.next().unwrap(), &[]);
1876 /// assert_eq!(iter.next().unwrap(), &[20]);
1877 /// assert!(iter.next().is_none());
1879 #[stable(feature = "rust1", since = "1.0.0")]
1881 pub fn split<F>(&self, pred: F) -> Split<'_, T, F>
1883 F: FnMut(&T) -> bool,
1885 Split::new(self, pred)
1888 /// Returns an iterator over mutable subslices separated by elements that
1889 /// match `pred`. The matched element is not contained in the subslices.
1894 /// let mut v = [10, 40, 30, 20, 60, 50];
1896 /// for group in v.split_mut(|num| *num % 3 == 0) {
1899 /// assert_eq!(v, [1, 40, 30, 1, 60, 1]);
1901 #[stable(feature = "rust1", since = "1.0.0")]
1903 pub fn split_mut<F>(&mut self, pred: F) -> SplitMut<'_, T, F>
1905 F: FnMut(&T) -> bool,
1907 SplitMut::new(self, pred)
1910 /// Returns an iterator over subslices separated by elements that match
1911 /// `pred`. The matched element is contained in the end of the previous
1912 /// subslice as a terminator.
1917 /// let slice = [10, 40, 33, 20];
1918 /// let mut iter = slice.split_inclusive(|num| num % 3 == 0);
1920 /// assert_eq!(iter.next().unwrap(), &[10, 40, 33]);
1921 /// assert_eq!(iter.next().unwrap(), &[20]);
1922 /// assert!(iter.next().is_none());
1925 /// If the last element of the slice is matched,
1926 /// that element will be considered the terminator of the preceding slice.
1927 /// That slice will be the last item returned by the iterator.
1930 /// let slice = [3, 10, 40, 33];
1931 /// let mut iter = slice.split_inclusive(|num| num % 3 == 0);
1933 /// assert_eq!(iter.next().unwrap(), &[3]);
1934 /// assert_eq!(iter.next().unwrap(), &[10, 40, 33]);
1935 /// assert!(iter.next().is_none());
1937 #[stable(feature = "split_inclusive", since = "1.51.0")]
1939 pub fn split_inclusive<F>(&self, pred: F) -> SplitInclusive<'_, T, F>
1941 F: FnMut(&T) -> bool,
1943 SplitInclusive::new(self, pred)
1946 /// Returns an iterator over mutable subslices separated by elements that
1947 /// match `pred`. The matched element is contained in the previous
1948 /// subslice as a terminator.
1953 /// let mut v = [10, 40, 30, 20, 60, 50];
1955 /// for group in v.split_inclusive_mut(|num| *num % 3 == 0) {
1956 /// let terminator_idx = group.len()-1;
1957 /// group[terminator_idx] = 1;
1959 /// assert_eq!(v, [10, 40, 1, 20, 1, 1]);
1961 #[stable(feature = "split_inclusive", since = "1.51.0")]
1963 pub fn split_inclusive_mut<F>(&mut self, pred: F) -> SplitInclusiveMut<'_, T, F>
1965 F: FnMut(&T) -> bool,
1967 SplitInclusiveMut::new(self, pred)
1970 /// Returns an iterator over subslices separated by elements that match
1971 /// `pred`, starting at the end of the slice and working backwards.
1972 /// The matched element is not contained in the subslices.
1977 /// let slice = [11, 22, 33, 0, 44, 55];
1978 /// let mut iter = slice.rsplit(|num| *num == 0);
1980 /// assert_eq!(iter.next().unwrap(), &[44, 55]);
1981 /// assert_eq!(iter.next().unwrap(), &[11, 22, 33]);
1982 /// assert_eq!(iter.next(), None);
1985 /// As with `split()`, if the first or last element is matched, an empty
1986 /// slice will be the first (or last) item returned by the iterator.
1989 /// let v = &[0, 1, 1, 2, 3, 5, 8];
1990 /// let mut it = v.rsplit(|n| *n % 2 == 0);
1991 /// assert_eq!(it.next().unwrap(), &[]);
1992 /// assert_eq!(it.next().unwrap(), &[3, 5]);
1993 /// assert_eq!(it.next().unwrap(), &[1, 1]);
1994 /// assert_eq!(it.next().unwrap(), &[]);
1995 /// assert_eq!(it.next(), None);
1997 #[stable(feature = "slice_rsplit", since = "1.27.0")]
1999 pub fn rsplit<F>(&self, pred: F) -> RSplit<'_, T, F>
2001 F: FnMut(&T) -> bool,
2003 RSplit::new(self, pred)
2006 /// Returns an iterator over mutable subslices separated by elements that
2007 /// match `pred`, starting at the end of the slice and working
2008 /// backwards. The matched element is not contained in the subslices.
2013 /// let mut v = [100, 400, 300, 200, 600, 500];
2015 /// let mut count = 0;
2016 /// for group in v.rsplit_mut(|num| *num % 3 == 0) {
2018 /// group[0] = count;
2020 /// assert_eq!(v, [3, 400, 300, 2, 600, 1]);
2023 #[stable(feature = "slice_rsplit", since = "1.27.0")]
2025 pub fn rsplit_mut<F>(&mut self, pred: F) -> RSplitMut<'_, T, F>
2027 F: FnMut(&T) -> bool,
2029 RSplitMut::new(self, pred)
2032 /// Returns an iterator over subslices separated by elements that match
2033 /// `pred`, limited to returning at most `n` items. The matched element is
2034 /// not contained in the subslices.
2036 /// The last element returned, if any, will contain the remainder of the
2041 /// Print the slice split once by numbers divisible by 3 (i.e., `[10, 40]`,
2042 /// `[20, 60, 50]`):
2045 /// let v = [10, 40, 30, 20, 60, 50];
2047 /// for group in v.splitn(2, |num| *num % 3 == 0) {
2048 /// println!("{group:?}");
2051 #[stable(feature = "rust1", since = "1.0.0")]
2053 pub fn splitn<F>(&self, n: usize, pred: F) -> SplitN<'_, T, F>
2055 F: FnMut(&T) -> bool,
2057 SplitN::new(self.split(pred), n)
2060 /// Returns an iterator over subslices separated by elements that match
2061 /// `pred`, limited to returning at most `n` items. The matched element is
2062 /// not contained in the subslices.
2064 /// The last element returned, if any, will contain the remainder of the
2070 /// let mut v = [10, 40, 30, 20, 60, 50];
2072 /// for group in v.splitn_mut(2, |num| *num % 3 == 0) {
2075 /// assert_eq!(v, [1, 40, 30, 1, 60, 50]);
2077 #[stable(feature = "rust1", since = "1.0.0")]
2079 pub fn splitn_mut<F>(&mut self, n: usize, pred: F) -> SplitNMut<'_, T, F>
2081 F: FnMut(&T) -> bool,
2083 SplitNMut::new(self.split_mut(pred), n)
2086 /// Returns an iterator over subslices separated by elements that match
2087 /// `pred` limited to returning at most `n` items. This starts at the end of
2088 /// the slice and works backwards. The matched element is not contained in
2091 /// The last element returned, if any, will contain the remainder of the
2096 /// Print the slice split once, starting from the end, by numbers divisible
2097 /// by 3 (i.e., `[50]`, `[10, 40, 30, 20]`):
2100 /// let v = [10, 40, 30, 20, 60, 50];
2102 /// for group in v.rsplitn(2, |num| *num % 3 == 0) {
2103 /// println!("{group:?}");
2106 #[stable(feature = "rust1", since = "1.0.0")]
2108 pub fn rsplitn<F>(&self, n: usize, pred: F) -> RSplitN<'_, T, F>
2110 F: FnMut(&T) -> bool,
2112 RSplitN::new(self.rsplit(pred), n)
2115 /// Returns an iterator over subslices separated by elements that match
2116 /// `pred` limited to returning at most `n` items. This starts at the end of
2117 /// the slice and works backwards. The matched element is not contained in
2120 /// The last element returned, if any, will contain the remainder of the
2126 /// let mut s = [10, 40, 30, 20, 60, 50];
2128 /// for group in s.rsplitn_mut(2, |num| *num % 3 == 0) {
2131 /// assert_eq!(s, [1, 40, 30, 20, 60, 1]);
2133 #[stable(feature = "rust1", since = "1.0.0")]
2135 pub fn rsplitn_mut<F>(&mut self, n: usize, pred: F) -> RSplitNMut<'_, T, F>
2137 F: FnMut(&T) -> bool,
2139 RSplitNMut::new(self.rsplit_mut(pred), n)
2142 /// Returns `true` if the slice contains an element with the given value.
2147 /// let v = [10, 40, 30];
2148 /// assert!(v.contains(&30));
2149 /// assert!(!v.contains(&50));
2152 /// If you do not have a `&T`, but some other value that you can compare
2153 /// with one (for example, `String` implements `PartialEq<str>`), you can
2154 /// use `iter().any`:
2157 /// let v = [String::from("hello"), String::from("world")]; // slice of `String`
2158 /// assert!(v.iter().any(|e| e == "hello")); // search with `&str`
2159 /// assert!(!v.iter().any(|e| e == "hi"));
2161 #[stable(feature = "rust1", since = "1.0.0")]
2164 pub fn contains(&self, x: &T) -> bool
2168 cmp::SliceContains::slice_contains(x, self)
2171 /// Returns `true` if `needle` is a prefix of the slice.
2176 /// let v = [10, 40, 30];
2177 /// assert!(v.starts_with(&[10]));
2178 /// assert!(v.starts_with(&[10, 40]));
2179 /// assert!(!v.starts_with(&[50]));
2180 /// assert!(!v.starts_with(&[10, 50]));
2183 /// Always returns `true` if `needle` is an empty slice:
2186 /// let v = &[10, 40, 30];
2187 /// assert!(v.starts_with(&[]));
2188 /// let v: &[u8] = &[];
2189 /// assert!(v.starts_with(&[]));
2191 #[stable(feature = "rust1", since = "1.0.0")]
2193 pub fn starts_with(&self, needle: &[T]) -> bool
2197 let n = needle.len();
2198 self.len() >= n && needle == &self[..n]
2201 /// Returns `true` if `needle` is a suffix of the slice.
2206 /// let v = [10, 40, 30];
2207 /// assert!(v.ends_with(&[30]));
2208 /// assert!(v.ends_with(&[40, 30]));
2209 /// assert!(!v.ends_with(&[50]));
2210 /// assert!(!v.ends_with(&[50, 30]));
2213 /// Always returns `true` if `needle` is an empty slice:
2216 /// let v = &[10, 40, 30];
2217 /// assert!(v.ends_with(&[]));
2218 /// let v: &[u8] = &[];
2219 /// assert!(v.ends_with(&[]));
2221 #[stable(feature = "rust1", since = "1.0.0")]
2223 pub fn ends_with(&self, needle: &[T]) -> bool
2227 let (m, n) = (self.len(), needle.len());
2228 m >= n && needle == &self[m - n..]
2231 /// Returns a subslice with the prefix removed.
2233 /// If the slice starts with `prefix`, returns the subslice after the prefix, wrapped in `Some`.
2234 /// If `prefix` is empty, simply returns the original slice.
2236 /// If the slice does not start with `prefix`, returns `None`.
2241 /// let v = &[10, 40, 30];
2242 /// assert_eq!(v.strip_prefix(&[10]), Some(&[40, 30][..]));
2243 /// assert_eq!(v.strip_prefix(&[10, 40]), Some(&[30][..]));
2244 /// assert_eq!(v.strip_prefix(&[50]), None);
2245 /// assert_eq!(v.strip_prefix(&[10, 50]), None);
2247 /// let prefix : &str = "he";
2248 /// assert_eq!(b"hello".strip_prefix(prefix.as_bytes()),
2249 /// Some(b"llo".as_ref()));
2251 #[must_use = "returns the subslice without modifying the original"]
2252 #[stable(feature = "slice_strip", since = "1.51.0")]
2253 pub fn strip_prefix<P: SlicePattern<Item = T> + ?Sized>(&self, prefix: &P) -> Option<&[T]>
2257 // This function will need rewriting if and when SlicePattern becomes more sophisticated.
2258 let prefix = prefix.as_slice();
2259 let n = prefix.len();
2260 if n <= self.len() {
2261 let (head, tail) = self.split_at(n);
2269 /// Returns a subslice with the suffix removed.
2271 /// If the slice ends with `suffix`, returns the subslice before the suffix, wrapped in `Some`.
2272 /// If `suffix` is empty, simply returns the original slice.
2274 /// If the slice does not end with `suffix`, returns `None`.
2279 /// let v = &[10, 40, 30];
2280 /// assert_eq!(v.strip_suffix(&[30]), Some(&[10, 40][..]));
2281 /// assert_eq!(v.strip_suffix(&[40, 30]), Some(&[10][..]));
2282 /// assert_eq!(v.strip_suffix(&[50]), None);
2283 /// assert_eq!(v.strip_suffix(&[50, 30]), None);
2285 #[must_use = "returns the subslice without modifying the original"]
2286 #[stable(feature = "slice_strip", since = "1.51.0")]
2287 pub fn strip_suffix<P: SlicePattern<Item = T> + ?Sized>(&self, suffix: &P) -> Option<&[T]>
2291 // This function will need rewriting if and when SlicePattern becomes more sophisticated.
2292 let suffix = suffix.as_slice();
2293 let (len, n) = (self.len(), suffix.len());
2295 let (head, tail) = self.split_at(len - n);
2303 /// Binary searches this sorted slice for a given element.
2305 /// If the value is found then [`Result::Ok`] is returned, containing the
2306 /// index of the matching element. If there are multiple matches, then any
2307 /// one of the matches could be returned. The index is chosen
2308 /// deterministically, but is subject to change in future versions of Rust.
2309 /// If the value is not found then [`Result::Err`] is returned, containing
2310 /// the index where a matching element could be inserted while maintaining
2313 /// See also [`binary_search_by`], [`binary_search_by_key`], and [`partition_point`].
2315 /// [`binary_search_by`]: slice::binary_search_by
2316 /// [`binary_search_by_key`]: slice::binary_search_by_key
2317 /// [`partition_point`]: slice::partition_point
2321 /// Looks up a series of four elements. The first is found, with a
2322 /// uniquely determined position; the second and third are not
2323 /// found; the fourth could match any position in `[1, 4]`.
2326 /// let s = [0, 1, 1, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55];
2328 /// assert_eq!(s.binary_search(&13), Ok(9));
2329 /// assert_eq!(s.binary_search(&4), Err(7));
2330 /// assert_eq!(s.binary_search(&100), Err(13));
2331 /// let r = s.binary_search(&1);
2332 /// assert!(match r { Ok(1..=4) => true, _ => false, });
2335 /// If you want to insert an item to a sorted vector, while maintaining
2339 /// let mut s = vec![0, 1, 1, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55];
2341 /// let idx = s.binary_search(&num).unwrap_or_else(|x| x);
2342 /// s.insert(idx, num);
2343 /// assert_eq!(s, [0, 1, 1, 1, 1, 2, 3, 5, 8, 13, 21, 34, 42, 55]);
2345 #[stable(feature = "rust1", since = "1.0.0")]
2346 pub fn binary_search(&self, x: &T) -> Result<usize, usize>
2350 self.binary_search_by(|p| p.cmp(x))
2353 /// Binary searches this sorted slice with a comparator function.
2355 /// The comparator function should implement an order consistent
2356 /// with the sort order of the underlying slice, returning an
2357 /// order code that indicates whether its argument is `Less`,
2358 /// `Equal` or `Greater` the desired target.
2360 /// If the value is found then [`Result::Ok`] is returned, containing the
2361 /// index of the matching element. If there are multiple matches, then any
2362 /// one of the matches could be returned. The index is chosen
2363 /// deterministically, but is subject to change in future versions of Rust.
2364 /// If the value is not found then [`Result::Err`] is returned, containing
2365 /// the index where a matching element could be inserted while maintaining
2368 /// See also [`binary_search`], [`binary_search_by_key`], and [`partition_point`].
2370 /// [`binary_search`]: slice::binary_search
2371 /// [`binary_search_by_key`]: slice::binary_search_by_key
2372 /// [`partition_point`]: slice::partition_point
2376 /// Looks up a series of four elements. The first is found, with a
2377 /// uniquely determined position; the second and third are not
2378 /// found; the fourth could match any position in `[1, 4]`.
2381 /// let s = [0, 1, 1, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55];
2384 /// assert_eq!(s.binary_search_by(|probe| probe.cmp(&seek)), Ok(9));
2386 /// assert_eq!(s.binary_search_by(|probe| probe.cmp(&seek)), Err(7));
2388 /// assert_eq!(s.binary_search_by(|probe| probe.cmp(&seek)), Err(13));
2390 /// let r = s.binary_search_by(|probe| probe.cmp(&seek));
2391 /// assert!(match r { Ok(1..=4) => true, _ => false, });
2393 #[stable(feature = "rust1", since = "1.0.0")]
2395 pub fn binary_search_by<'a, F>(&'a self, mut f: F) -> Result<usize, usize>
2397 F: FnMut(&'a T) -> Ordering,
2399 let mut size = self.len();
2401 let mut right = size;
2402 while left < right {
2403 let mid = left + size / 2;
2405 // SAFETY: the call is made safe by the following invariants:
2407 // - `mid < size`: `mid` is limited by `[left; right)` bound.
2408 let cmp = f(unsafe { self.get_unchecked(mid) });
2410 // The reason why we use if/else control flow rather than match
2411 // is because match reorders comparison operations, which is perf sensitive.
2412 // This is x86 asm for u8: https://rust.godbolt.org/z/8Y8Pra.
2415 } else if cmp == Greater {
2418 // SAFETY: same as the `get_unchecked` above
2419 unsafe { crate::intrinsics::assume(mid < self.len()) };
2423 size = right - left;
2428 /// Binary searches this sorted slice with a key extraction function.
2430 /// Assumes that the slice is sorted by the key, for instance with
2431 /// [`sort_by_key`] using the same key extraction function.
2433 /// If the value is found then [`Result::Ok`] is returned, containing the
2434 /// index of the matching element. If there are multiple matches, then any
2435 /// one of the matches could be returned. The index is chosen
2436 /// deterministically, but is subject to change in future versions of Rust.
2437 /// If the value is not found then [`Result::Err`] is returned, containing
2438 /// the index where a matching element could be inserted while maintaining
2441 /// See also [`binary_search`], [`binary_search_by`], and [`partition_point`].
2443 /// [`sort_by_key`]: slice::sort_by_key
2444 /// [`binary_search`]: slice::binary_search
2445 /// [`binary_search_by`]: slice::binary_search_by
2446 /// [`partition_point`]: slice::partition_point
2450 /// Looks up a series of four elements in a slice of pairs sorted by
2451 /// their second elements. The first is found, with a uniquely
2452 /// determined position; the second and third are not found; the
2453 /// fourth could match any position in `[1, 4]`.
2456 /// let s = [(0, 0), (2, 1), (4, 1), (5, 1), (3, 1),
2457 /// (1, 2), (2, 3), (4, 5), (5, 8), (3, 13),
2458 /// (1, 21), (2, 34), (4, 55)];
2460 /// assert_eq!(s.binary_search_by_key(&13, |&(a, b)| b), Ok(9));
2461 /// assert_eq!(s.binary_search_by_key(&4, |&(a, b)| b), Err(7));
2462 /// assert_eq!(s.binary_search_by_key(&100, |&(a, b)| b), Err(13));
2463 /// let r = s.binary_search_by_key(&1, |&(a, b)| b);
2464 /// assert!(match r { Ok(1..=4) => true, _ => false, });
2466 // Lint rustdoc::broken_intra_doc_links is allowed as `slice::sort_by_key` is
2467 // in crate `alloc`, and as such doesn't exists yet when building `core`: #74481.
2468 // This breaks links when slice is displayed in core, but changing it to use relative links
2469 // would break when the item is re-exported. So allow the core links to be broken for now.
2470 #[allow(rustdoc::broken_intra_doc_links)]
2471 #[stable(feature = "slice_binary_search_by_key", since = "1.10.0")]
2473 pub fn binary_search_by_key<'a, B, F>(&'a self, b: &B, mut f: F) -> Result<usize, usize>
2475 F: FnMut(&'a T) -> B,
2478 self.binary_search_by(|k| f(k).cmp(b))
2481 /// Sorts the slice, but might not preserve the order of equal elements.
2483 /// This sort is unstable (i.e., may reorder equal elements), in-place
2484 /// (i.e., does not allocate), and *O*(*n* \* log(*n*)) worst-case.
2486 /// # Current implementation
2488 /// The current algorithm is based on [pattern-defeating quicksort][pdqsort] by Orson Peters,
2489 /// which combines the fast average case of randomized quicksort with the fast worst case of
2490 /// heapsort, while achieving linear time on slices with certain patterns. It uses some
2491 /// randomization to avoid degenerate cases, but with a fixed seed to always provide
2492 /// deterministic behavior.
2494 /// It is typically faster than stable sorting, except in a few special cases, e.g., when the
2495 /// slice consists of several concatenated sorted sequences.
2500 /// let mut v = [-5, 4, 1, -3, 2];
2502 /// v.sort_unstable();
2503 /// assert!(v == [-5, -3, 1, 2, 4]);
2506 /// [pdqsort]: https://github.com/orlp/pdqsort
2507 #[stable(feature = "sort_unstable", since = "1.20.0")]
2509 pub fn sort_unstable(&mut self)
2513 sort::quicksort(self, |a, b| a.lt(b));
2516 /// Sorts the slice with a comparator function, but might not preserve the order of equal
2519 /// This sort is unstable (i.e., may reorder equal elements), in-place
2520 /// (i.e., does not allocate), and *O*(*n* \* log(*n*)) worst-case.
2522 /// The comparator function must define a total ordering for the elements in the slice. If
2523 /// the ordering is not total, the order of the elements is unspecified. An order is a
2524 /// total order if it is (for all `a`, `b` and `c`):
2526 /// * total and antisymmetric: exactly one of `a < b`, `a == b` or `a > b` is true, and
2527 /// * transitive, `a < b` and `b < c` implies `a < c`. The same must hold for both `==` and `>`.
2529 /// For example, while [`f64`] doesn't implement [`Ord`] because `NaN != NaN`, we can use
2530 /// `partial_cmp` as our sort function when we know the slice doesn't contain a `NaN`.
2533 /// let mut floats = [5f64, 4.0, 1.0, 3.0, 2.0];
2534 /// floats.sort_unstable_by(|a, b| a.partial_cmp(b).unwrap());
2535 /// assert_eq!(floats, [1.0, 2.0, 3.0, 4.0, 5.0]);
2538 /// # Current implementation
2540 /// The current algorithm is based on [pattern-defeating quicksort][pdqsort] by Orson Peters,
2541 /// which combines the fast average case of randomized quicksort with the fast worst case of
2542 /// heapsort, while achieving linear time on slices with certain patterns. It uses some
2543 /// randomization to avoid degenerate cases, but with a fixed seed to always provide
2544 /// deterministic behavior.
2546 /// It is typically faster than stable sorting, except in a few special cases, e.g., when the
2547 /// slice consists of several concatenated sorted sequences.
2552 /// let mut v = [5, 4, 1, 3, 2];
2553 /// v.sort_unstable_by(|a, b| a.cmp(b));
2554 /// assert!(v == [1, 2, 3, 4, 5]);
2556 /// // reverse sorting
2557 /// v.sort_unstable_by(|a, b| b.cmp(a));
2558 /// assert!(v == [5, 4, 3, 2, 1]);
2561 /// [pdqsort]: https://github.com/orlp/pdqsort
2562 #[stable(feature = "sort_unstable", since = "1.20.0")]
2564 pub fn sort_unstable_by<F>(&mut self, mut compare: F)
2566 F: FnMut(&T, &T) -> Ordering,
2568 sort::quicksort(self, |a, b| compare(a, b) == Ordering::Less);
2571 /// Sorts the slice with a key extraction function, but might not preserve the order of equal
2574 /// This sort is unstable (i.e., may reorder equal elements), in-place
2575 /// (i.e., does not allocate), and *O*(m \* *n* \* log(*n*)) worst-case, where the key function is
2578 /// # Current implementation
2580 /// The current algorithm is based on [pattern-defeating quicksort][pdqsort] by Orson Peters,
2581 /// which combines the fast average case of randomized quicksort with the fast worst case of
2582 /// heapsort, while achieving linear time on slices with certain patterns. It uses some
2583 /// randomization to avoid degenerate cases, but with a fixed seed to always provide
2584 /// deterministic behavior.
2586 /// Due to its key calling strategy, [`sort_unstable_by_key`](#method.sort_unstable_by_key)
2587 /// is likely to be slower than [`sort_by_cached_key`](#method.sort_by_cached_key) in
2588 /// cases where the key function is expensive.
2593 /// let mut v = [-5i32, 4, 1, -3, 2];
2595 /// v.sort_unstable_by_key(|k| k.abs());
2596 /// assert!(v == [1, 2, -3, 4, -5]);
2599 /// [pdqsort]: https://github.com/orlp/pdqsort
2600 #[stable(feature = "sort_unstable", since = "1.20.0")]
2602 pub fn sort_unstable_by_key<K, F>(&mut self, mut f: F)
2607 sort::quicksort(self, |a, b| f(a).lt(&f(b)));
2610 /// Reorder the slice such that the element at `index` is at its final sorted position.
2612 /// This reordering has the additional property that any value at position `i < index` will be
2613 /// less than or equal to any value at a position `j > index`. Additionally, this reordering is
2614 /// unstable (i.e. any number of equal elements may end up at position `index`), in-place
2615 /// (i.e. does not allocate), and *O*(*n*) worst-case. This function is also/ known as "kth
2616 /// element" in other libraries. It returns a triplet of the following values: all elements less
2617 /// than the one at the given index, the value at the given index, and all elements greater than
2618 /// the one at the given index.
2620 /// # Current implementation
2622 /// The current algorithm is based on the quickselect portion of the same quicksort algorithm
2623 /// used for [`sort_unstable`].
2625 /// [`sort_unstable`]: slice::sort_unstable
2629 /// Panics when `index >= len()`, meaning it always panics on empty slices.
2634 /// let mut v = [-5i32, 4, 1, -3, 2];
2636 /// // Find the median
2637 /// v.select_nth_unstable(2);
2639 /// // We are only guaranteed the slice will be one of the following, based on the way we sort
2640 /// // about the specified index.
2641 /// assert!(v == [-3, -5, 1, 2, 4] ||
2642 /// v == [-5, -3, 1, 2, 4] ||
2643 /// v == [-3, -5, 1, 4, 2] ||
2644 /// v == [-5, -3, 1, 4, 2]);
2646 #[stable(feature = "slice_select_nth_unstable", since = "1.49.0")]
2648 pub fn select_nth_unstable(&mut self, index: usize) -> (&mut [T], &mut T, &mut [T])
2652 let mut f = |a: &T, b: &T| a.lt(b);
2653 sort::partition_at_index(self, index, &mut f)
2656 /// Reorder the slice with a comparator function such that the element at `index` is at its
2657 /// final sorted position.
2659 /// This reordering has the additional property that any value at position `i < index` will be
2660 /// less than or equal to any value at a position `j > index` using the comparator function.
2661 /// Additionally, this reordering is unstable (i.e. any number of equal elements may end up at
2662 /// position `index`), in-place (i.e. does not allocate), and *O*(*n*) worst-case. This function
2663 /// is also known as "kth element" in other libraries. It returns a triplet of the following
2664 /// values: all elements less than the one at the given index, the value at the given index,
2665 /// and all elements greater than the one at the given index, using the provided comparator
2668 /// # Current implementation
2670 /// The current algorithm is based on the quickselect portion of the same quicksort algorithm
2671 /// used for [`sort_unstable`].
2673 /// [`sort_unstable`]: slice::sort_unstable
2677 /// Panics when `index >= len()`, meaning it always panics on empty slices.
2682 /// let mut v = [-5i32, 4, 1, -3, 2];
2684 /// // Find the median as if the slice were sorted in descending order.
2685 /// v.select_nth_unstable_by(2, |a, b| b.cmp(a));
2687 /// // We are only guaranteed the slice will be one of the following, based on the way we sort
2688 /// // about the specified index.
2689 /// assert!(v == [2, 4, 1, -5, -3] ||
2690 /// v == [2, 4, 1, -3, -5] ||
2691 /// v == [4, 2, 1, -5, -3] ||
2692 /// v == [4, 2, 1, -3, -5]);
2694 #[stable(feature = "slice_select_nth_unstable", since = "1.49.0")]
2696 pub fn select_nth_unstable_by<F>(
2700 ) -> (&mut [T], &mut T, &mut [T])
2702 F: FnMut(&T, &T) -> Ordering,
2704 let mut f = |a: &T, b: &T| compare(a, b) == Less;
2705 sort::partition_at_index(self, index, &mut f)
2708 /// Reorder the slice with a key extraction function such that the element at `index` is at its
2709 /// final sorted position.
2711 /// This reordering has the additional property that any value at position `i < index` will be
2712 /// less than or equal to any value at a position `j > index` using the key extraction function.
2713 /// Additionally, this reordering is unstable (i.e. any number of equal elements may end up at
2714 /// position `index`), in-place (i.e. does not allocate), and *O*(*n*) worst-case. This function
2715 /// is also known as "kth element" in other libraries. It returns a triplet of the following
2716 /// values: all elements less than the one at the given index, the value at the given index, and
2717 /// all elements greater than the one at the given index, using the provided key extraction
2720 /// # Current implementation
2722 /// The current algorithm is based on the quickselect portion of the same quicksort algorithm
2723 /// used for [`sort_unstable`].
2725 /// [`sort_unstable`]: slice::sort_unstable
2729 /// Panics when `index >= len()`, meaning it always panics on empty slices.
2734 /// let mut v = [-5i32, 4, 1, -3, 2];
2736 /// // Return the median as if the array were sorted according to absolute value.
2737 /// v.select_nth_unstable_by_key(2, |a| a.abs());
2739 /// // We are only guaranteed the slice will be one of the following, based on the way we sort
2740 /// // about the specified index.
2741 /// assert!(v == [1, 2, -3, 4, -5] ||
2742 /// v == [1, 2, -3, -5, 4] ||
2743 /// v == [2, 1, -3, 4, -5] ||
2744 /// v == [2, 1, -3, -5, 4]);
2746 #[stable(feature = "slice_select_nth_unstable", since = "1.49.0")]
2748 pub fn select_nth_unstable_by_key<K, F>(
2752 ) -> (&mut [T], &mut T, &mut [T])
2757 let mut g = |a: &T, b: &T| f(a).lt(&f(b));
2758 sort::partition_at_index(self, index, &mut g)
2761 /// Moves all consecutive repeated elements to the end of the slice according to the
2762 /// [`PartialEq`] trait implementation.
2764 /// Returns two slices. The first contains no consecutive repeated elements.
2765 /// The second contains all the duplicates in no specified order.
2767 /// If the slice is sorted, the first returned slice contains no duplicates.
2772 /// #![feature(slice_partition_dedup)]
2774 /// let mut slice = [1, 2, 2, 3, 3, 2, 1, 1];
2776 /// let (dedup, duplicates) = slice.partition_dedup();
2778 /// assert_eq!(dedup, [1, 2, 3, 2, 1]);
2779 /// assert_eq!(duplicates, [2, 3, 1]);
2781 #[unstable(feature = "slice_partition_dedup", issue = "54279")]
2783 pub fn partition_dedup(&mut self) -> (&mut [T], &mut [T])
2787 self.partition_dedup_by(|a, b| a == b)
2790 /// Moves all but the first of consecutive elements to the end of the slice satisfying
2791 /// a given equality relation.
2793 /// Returns two slices. The first contains no consecutive repeated elements.
2794 /// The second contains all the duplicates in no specified order.
2796 /// The `same_bucket` function is passed references to two elements from the slice and
2797 /// must determine if the elements compare equal. The elements are passed in opposite order
2798 /// from their order in the slice, so if `same_bucket(a, b)` returns `true`, `a` is moved
2799 /// at the end of the slice.
2801 /// If the slice is sorted, the first returned slice contains no duplicates.
2806 /// #![feature(slice_partition_dedup)]
2808 /// let mut slice = ["foo", "Foo", "BAZ", "Bar", "bar", "baz", "BAZ"];
2810 /// let (dedup, duplicates) = slice.partition_dedup_by(|a, b| a.eq_ignore_ascii_case(b));
2812 /// assert_eq!(dedup, ["foo", "BAZ", "Bar", "baz"]);
2813 /// assert_eq!(duplicates, ["bar", "Foo", "BAZ"]);
2815 #[unstable(feature = "slice_partition_dedup", issue = "54279")]
2817 pub fn partition_dedup_by<F>(&mut self, mut same_bucket: F) -> (&mut [T], &mut [T])
2819 F: FnMut(&mut T, &mut T) -> bool,
2821 // Although we have a mutable reference to `self`, we cannot make
2822 // *arbitrary* changes. The `same_bucket` calls could panic, so we
2823 // must ensure that the slice is in a valid state at all times.
2825 // The way that we handle this is by using swaps; we iterate
2826 // over all the elements, swapping as we go so that at the end
2827 // the elements we wish to keep are in the front, and those we
2828 // wish to reject are at the back. We can then split the slice.
2829 // This operation is still `O(n)`.
2831 // Example: We start in this state, where `r` represents "next
2832 // read" and `w` represents "next_write`.
2835 // +---+---+---+---+---+---+
2836 // | 0 | 1 | 1 | 2 | 3 | 3 |
2837 // +---+---+---+---+---+---+
2840 // Comparing self[r] against self[w-1], this is not a duplicate, so
2841 // we swap self[r] and self[w] (no effect as r==w) and then increment both
2842 // r and w, leaving us with:
2845 // +---+---+---+---+---+---+
2846 // | 0 | 1 | 1 | 2 | 3 | 3 |
2847 // +---+---+---+---+---+---+
2850 // Comparing self[r] against self[w-1], this value is a duplicate,
2851 // so we increment `r` but leave everything else unchanged:
2854 // +---+---+---+---+---+---+
2855 // | 0 | 1 | 1 | 2 | 3 | 3 |
2856 // +---+---+---+---+---+---+
2859 // Comparing self[r] against self[w-1], this is not a duplicate,
2860 // so swap self[r] and self[w] and advance r and w:
2863 // +---+---+---+---+---+---+
2864 // | 0 | 1 | 2 | 1 | 3 | 3 |
2865 // +---+---+---+---+---+---+
2868 // Not a duplicate, repeat:
2871 // +---+---+---+---+---+---+
2872 // | 0 | 1 | 2 | 3 | 1 | 3 |
2873 // +---+---+---+---+---+---+
2876 // Duplicate, advance r. End of slice. Split at w.
2878 let len = self.len();
2880 return (self, &mut []);
2883 let ptr = self.as_mut_ptr();
2884 let mut next_read: usize = 1;
2885 let mut next_write: usize = 1;
2887 // SAFETY: the `while` condition guarantees `next_read` and `next_write`
2888 // are less than `len`, thus are inside `self`. `prev_ptr_write` points to
2889 // one element before `ptr_write`, but `next_write` starts at 1, so
2890 // `prev_ptr_write` is never less than 0 and is inside the slice.
2891 // This fulfils the requirements for dereferencing `ptr_read`, `prev_ptr_write`
2892 // and `ptr_write`, and for using `ptr.add(next_read)`, `ptr.add(next_write - 1)`
2893 // and `prev_ptr_write.offset(1)`.
2895 // `next_write` is also incremented at most once per loop at most meaning
2896 // no element is skipped when it may need to be swapped.
2898 // `ptr_read` and `prev_ptr_write` never point to the same element. This
2899 // is required for `&mut *ptr_read`, `&mut *prev_ptr_write` to be safe.
2900 // The explanation is simply that `next_read >= next_write` is always true,
2901 // thus `next_read > next_write - 1` is too.
2903 // Avoid bounds checks by using raw pointers.
2904 while next_read < len {
2905 let ptr_read = ptr.add(next_read);
2906 let prev_ptr_write = ptr.add(next_write - 1);
2907 if !same_bucket(&mut *ptr_read, &mut *prev_ptr_write) {
2908 if next_read != next_write {
2909 let ptr_write = prev_ptr_write.offset(1);
2910 mem::swap(&mut *ptr_read, &mut *ptr_write);
2918 self.split_at_mut(next_write)
2921 /// Moves all but the first of consecutive elements to the end of the slice that resolve
2922 /// to the same key.
2924 /// Returns two slices. The first contains no consecutive repeated elements.
2925 /// The second contains all the duplicates in no specified order.
2927 /// If the slice is sorted, the first returned slice contains no duplicates.
2932 /// #![feature(slice_partition_dedup)]
2934 /// let mut slice = [10, 20, 21, 30, 30, 20, 11, 13];
2936 /// let (dedup, duplicates) = slice.partition_dedup_by_key(|i| *i / 10);
2938 /// assert_eq!(dedup, [10, 20, 30, 20, 11]);
2939 /// assert_eq!(duplicates, [21, 30, 13]);
2941 #[unstable(feature = "slice_partition_dedup", issue = "54279")]
2943 pub fn partition_dedup_by_key<K, F>(&mut self, mut key: F) -> (&mut [T], &mut [T])
2945 F: FnMut(&mut T) -> K,
2948 self.partition_dedup_by(|a, b| key(a) == key(b))
2951 /// Rotates the slice in-place such that the first `mid` elements of the
2952 /// slice move to the end while the last `self.len() - mid` elements move to
2953 /// the front. After calling `rotate_left`, the element previously at index
2954 /// `mid` will become the first element in the slice.
2958 /// This function will panic if `mid` is greater than the length of the
2959 /// slice. Note that `mid == self.len()` does _not_ panic and is a no-op
2964 /// Takes linear (in `self.len()`) time.
2969 /// let mut a = ['a', 'b', 'c', 'd', 'e', 'f'];
2970 /// a.rotate_left(2);
2971 /// assert_eq!(a, ['c', 'd', 'e', 'f', 'a', 'b']);
2974 /// Rotating a subslice:
2977 /// let mut a = ['a', 'b', 'c', 'd', 'e', 'f'];
2978 /// a[1..5].rotate_left(1);
2979 /// assert_eq!(a, ['a', 'c', 'd', 'e', 'b', 'f']);
2981 #[stable(feature = "slice_rotate", since = "1.26.0")]
2982 pub fn rotate_left(&mut self, mid: usize) {
2983 assert!(mid <= self.len());
2984 let k = self.len() - mid;
2985 let p = self.as_mut_ptr();
2987 // SAFETY: The range `[p.add(mid) - mid, p.add(mid) + k)` is trivially
2988 // valid for reading and writing, as required by `ptr_rotate`.
2990 rotate::ptr_rotate(mid, p.add(mid), k);
2994 /// Rotates the slice in-place such that the first `self.len() - k`
2995 /// elements of the slice move to the end while the last `k` elements move
2996 /// to the front. After calling `rotate_right`, the element previously at
2997 /// index `self.len() - k` will become the first element in the slice.
3001 /// This function will panic if `k` is greater than the length of the
3002 /// slice. Note that `k == self.len()` does _not_ panic and is a no-op
3007 /// Takes linear (in `self.len()`) time.
3012 /// let mut a = ['a', 'b', 'c', 'd', 'e', 'f'];
3013 /// a.rotate_right(2);
3014 /// assert_eq!(a, ['e', 'f', 'a', 'b', 'c', 'd']);
3017 /// Rotate a subslice:
3020 /// let mut a = ['a', 'b', 'c', 'd', 'e', 'f'];
3021 /// a[1..5].rotate_right(1);
3022 /// assert_eq!(a, ['a', 'e', 'b', 'c', 'd', 'f']);
3024 #[stable(feature = "slice_rotate", since = "1.26.0")]
3025 pub fn rotate_right(&mut self, k: usize) {
3026 assert!(k <= self.len());
3027 let mid = self.len() - k;
3028 let p = self.as_mut_ptr();
3030 // SAFETY: The range `[p.add(mid) - mid, p.add(mid) + k)` is trivially
3031 // valid for reading and writing, as required by `ptr_rotate`.
3033 rotate::ptr_rotate(mid, p.add(mid), k);
3037 /// Fills `self` with elements by cloning `value`.
3042 /// let mut buf = vec![0; 10];
3044 /// assert_eq!(buf, vec![1; 10]);
3046 #[doc(alias = "memset")]
3047 #[stable(feature = "slice_fill", since = "1.50.0")]
3048 pub fn fill(&mut self, value: T)
3052 specialize::SpecFill::spec_fill(self, value);
3055 /// Fills `self` with elements returned by calling a closure repeatedly.
3057 /// This method uses a closure to create new values. If you'd rather
3058 /// [`Clone`] a given value, use [`fill`]. If you want to use the [`Default`]
3059 /// trait to generate values, you can pass [`Default::default`] as the
3062 /// [`fill`]: slice::fill
3067 /// let mut buf = vec![1; 10];
3068 /// buf.fill_with(Default::default);
3069 /// assert_eq!(buf, vec![0; 10]);
3071 #[doc(alias = "memset")]
3072 #[stable(feature = "slice_fill_with", since = "1.51.0")]
3073 pub fn fill_with<F>(&mut self, mut f: F)
3082 /// Copies the elements from `src` into `self`.
3084 /// The length of `src` must be the same as `self`.
3088 /// This function will panic if the two slices have different lengths.
3092 /// Cloning two elements from a slice into another:
3095 /// let src = [1, 2, 3, 4];
3096 /// let mut dst = [0, 0];
3098 /// // Because the slices have to be the same length,
3099 /// // we slice the source slice from four elements
3100 /// // to two. It will panic if we don't do this.
3101 /// dst.clone_from_slice(&src[2..]);
3103 /// assert_eq!(src, [1, 2, 3, 4]);
3104 /// assert_eq!(dst, [3, 4]);
3107 /// Rust enforces that there can only be one mutable reference with no
3108 /// immutable references to a particular piece of data in a particular
3109 /// scope. Because of this, attempting to use `clone_from_slice` on a
3110 /// single slice will result in a compile failure:
3113 /// let mut slice = [1, 2, 3, 4, 5];
3115 /// slice[..2].clone_from_slice(&slice[3..]); // compile fail!
3118 /// To work around this, we can use [`split_at_mut`] to create two distinct
3119 /// sub-slices from a slice:
3122 /// let mut slice = [1, 2, 3, 4, 5];
3125 /// let (left, right) = slice.split_at_mut(2);
3126 /// left.clone_from_slice(&right[1..]);
3129 /// assert_eq!(slice, [4, 5, 3, 4, 5]);
3132 /// [`copy_from_slice`]: slice::copy_from_slice
3133 /// [`split_at_mut`]: slice::split_at_mut
3134 #[stable(feature = "clone_from_slice", since = "1.7.0")]
3136 pub fn clone_from_slice(&mut self, src: &[T])
3140 self.spec_clone_from(src);
3143 /// Copies all elements from `src` into `self`, using a memcpy.
3145 /// The length of `src` must be the same as `self`.
3147 /// If `T` does not implement `Copy`, use [`clone_from_slice`].
3151 /// This function will panic if the two slices have different lengths.
3155 /// Copying two elements from a slice into another:
3158 /// let src = [1, 2, 3, 4];
3159 /// let mut dst = [0, 0];
3161 /// // Because the slices have to be the same length,
3162 /// // we slice the source slice from four elements
3163 /// // to two. It will panic if we don't do this.
3164 /// dst.copy_from_slice(&src[2..]);
3166 /// assert_eq!(src, [1, 2, 3, 4]);
3167 /// assert_eq!(dst, [3, 4]);
3170 /// Rust enforces that there can only be one mutable reference with no
3171 /// immutable references to a particular piece of data in a particular
3172 /// scope. Because of this, attempting to use `copy_from_slice` on a
3173 /// single slice will result in a compile failure:
3176 /// let mut slice = [1, 2, 3, 4, 5];
3178 /// slice[..2].copy_from_slice(&slice[3..]); // compile fail!
3181 /// To work around this, we can use [`split_at_mut`] to create two distinct
3182 /// sub-slices from a slice:
3185 /// let mut slice = [1, 2, 3, 4, 5];
3188 /// let (left, right) = slice.split_at_mut(2);
3189 /// left.copy_from_slice(&right[1..]);
3192 /// assert_eq!(slice, [4, 5, 3, 4, 5]);
3195 /// [`clone_from_slice`]: slice::clone_from_slice
3196 /// [`split_at_mut`]: slice::split_at_mut
3197 #[doc(alias = "memcpy")]
3198 #[stable(feature = "copy_from_slice", since = "1.9.0")]
3200 pub fn copy_from_slice(&mut self, src: &[T])
3204 // The panic code path was put into a cold function to not bloat the
3209 fn len_mismatch_fail(dst_len: usize, src_len: usize) -> ! {
3211 "source slice length ({}) does not match destination slice length ({})",
3216 if self.len() != src.len() {
3217 len_mismatch_fail(self.len(), src.len());
3220 // SAFETY: `self` is valid for `self.len()` elements by definition, and `src` was
3221 // checked to have the same length. The slices cannot overlap because
3222 // mutable references are exclusive.
3224 ptr::copy_nonoverlapping(src.as_ptr(), self.as_mut_ptr(), self.len());
3228 /// Copies elements from one part of the slice to another part of itself,
3229 /// using a memmove.
3231 /// `src` is the range within `self` to copy from. `dest` is the starting
3232 /// index of the range within `self` to copy to, which will have the same
3233 /// length as `src`. The two ranges may overlap. The ends of the two ranges
3234 /// must be less than or equal to `self.len()`.
3238 /// This function will panic if either range exceeds the end of the slice,
3239 /// or if the end of `src` is before the start.
3243 /// Copying four bytes within a slice:
3246 /// let mut bytes = *b"Hello, World!";
3248 /// bytes.copy_within(1..5, 8);
3250 /// assert_eq!(&bytes, b"Hello, Wello!");
3252 #[stable(feature = "copy_within", since = "1.37.0")]
3254 pub fn copy_within<R: RangeBounds<usize>>(&mut self, src: R, dest: usize)
3258 let Range { start: src_start, end: src_end } = slice::range(src, ..self.len());
3259 let count = src_end - src_start;
3260 assert!(dest <= self.len() - count, "dest is out of bounds");
3261 // SAFETY: the conditions for `ptr::copy` have all been checked above,
3262 // as have those for `ptr::add`.
3264 // Derive both `src_ptr` and `dest_ptr` from the same loan
3265 let ptr = self.as_mut_ptr();
3266 let src_ptr = ptr.add(src_start);
3267 let dest_ptr = ptr.add(dest);
3268 ptr::copy(src_ptr, dest_ptr, count);
3272 /// Swaps all elements in `self` with those in `other`.
3274 /// The length of `other` must be the same as `self`.
3278 /// This function will panic if the two slices have different lengths.
3282 /// Swapping two elements across slices:
3285 /// let mut slice1 = [0, 0];
3286 /// let mut slice2 = [1, 2, 3, 4];
3288 /// slice1.swap_with_slice(&mut slice2[2..]);
3290 /// assert_eq!(slice1, [3, 4]);
3291 /// assert_eq!(slice2, [1, 2, 0, 0]);
3294 /// Rust enforces that there can only be one mutable reference to a
3295 /// particular piece of data in a particular scope. Because of this,
3296 /// attempting to use `swap_with_slice` on a single slice will result in
3297 /// a compile failure:
3300 /// let mut slice = [1, 2, 3, 4, 5];
3301 /// slice[..2].swap_with_slice(&mut slice[3..]); // compile fail!
3304 /// To work around this, we can use [`split_at_mut`] to create two distinct
3305 /// mutable sub-slices from a slice:
3308 /// let mut slice = [1, 2, 3, 4, 5];
3311 /// let (left, right) = slice.split_at_mut(2);
3312 /// left.swap_with_slice(&mut right[1..]);
3315 /// assert_eq!(slice, [4, 5, 3, 1, 2]);
3318 /// [`split_at_mut`]: slice::split_at_mut
3319 #[stable(feature = "swap_with_slice", since = "1.27.0")]
3321 pub fn swap_with_slice(&mut self, other: &mut [T]) {
3322 assert!(self.len() == other.len(), "destination and source slices have different lengths");
3323 // SAFETY: `self` is valid for `self.len()` elements by definition, and `src` was
3324 // checked to have the same length. The slices cannot overlap because
3325 // mutable references are exclusive.
3327 ptr::swap_nonoverlapping(self.as_mut_ptr(), other.as_mut_ptr(), self.len());
3331 /// Function to calculate lengths of the middle and trailing slice for `align_to{,_mut}`.
3332 fn align_to_offsets<U>(&self) -> (usize, usize) {
3333 // What we gonna do about `rest` is figure out what multiple of `U`s we can put in a
3334 // lowest number of `T`s. And how many `T`s we need for each such "multiple".
3336 // Consider for example T=u8 U=u16. Then we can put 1 U in 2 Ts. Simple. Now, consider
3337 // for example a case where size_of::<T> = 16, size_of::<U> = 24. We can put 2 Us in
3338 // place of every 3 Ts in the `rest` slice. A bit more complicated.
3340 // Formula to calculate this is:
3342 // Us = lcm(size_of::<T>, size_of::<U>) / size_of::<U>
3343 // Ts = lcm(size_of::<T>, size_of::<U>) / size_of::<T>
3345 // Expanded and simplified:
3347 // Us = size_of::<T> / gcd(size_of::<T>, size_of::<U>)
3348 // Ts = size_of::<U> / gcd(size_of::<T>, size_of::<U>)
3350 // Luckily since all this is constant-evaluated... performance here matters not!
3352 fn gcd(a: usize, b: usize) -> usize {
3353 use crate::intrinsics;
3354 // iterative stein’s algorithm
3355 // We should still make this `const fn` (and revert to recursive algorithm if we do)
3356 // because relying on llvm to consteval all this is… well, it makes me uncomfortable.
3358 // SAFETY: `a` and `b` are checked to be non-zero values.
3359 let (ctz_a, mut ctz_b) = unsafe {
3366 (intrinsics::cttz_nonzero(a), intrinsics::cttz_nonzero(b))
3368 let k = ctz_a.min(ctz_b);
3369 let mut a = a >> ctz_a;
3372 // remove all factors of 2 from b
3375 mem::swap(&mut a, &mut b);
3378 // SAFETY: `b` is checked to be non-zero.
3383 ctz_b = intrinsics::cttz_nonzero(b);
3388 let gcd: usize = gcd(mem::size_of::<T>(), mem::size_of::<U>());
3389 let ts: usize = mem::size_of::<U>() / gcd;
3390 let us: usize = mem::size_of::<T>() / gcd;
3392 // Armed with this knowledge, we can find how many `U`s we can fit!
3393 let us_len = self.len() / ts * us;
3394 // And how many `T`s will be in the trailing slice!
3395 let ts_len = self.len() % ts;
3399 /// Transmute the slice to a slice of another type, ensuring alignment of the types is
3402 /// This method splits the slice into three distinct slices: prefix, correctly aligned middle
3403 /// slice of a new type, and the suffix slice. The method may make the middle slice the greatest
3404 /// length possible for a given type and input slice, but only your algorithm's performance
3405 /// should depend on that, not its correctness. It is permissible for all of the input data to
3406 /// be returned as the prefix or suffix slice.
3408 /// This method has no purpose when either input element `T` or output element `U` are
3409 /// zero-sized and will return the original slice without splitting anything.
3413 /// This method is essentially a `transmute` with respect to the elements in the returned
3414 /// middle slice, so all the usual caveats pertaining to `transmute::<T, U>` also apply here.
3422 /// let bytes: [u8; 7] = [1, 2, 3, 4, 5, 6, 7];
3423 /// let (prefix, shorts, suffix) = bytes.align_to::<u16>();
3424 /// // less_efficient_algorithm_for_bytes(prefix);
3425 /// // more_efficient_algorithm_for_aligned_shorts(shorts);
3426 /// // less_efficient_algorithm_for_bytes(suffix);
3429 #[stable(feature = "slice_align_to", since = "1.30.0")]
3431 pub unsafe fn align_to<U>(&self) -> (&[T], &[U], &[T]) {
3432 // Note that most of this function will be constant-evaluated,
3433 if mem::size_of::<U>() == 0 || mem::size_of::<T>() == 0 {
3434 // handle ZSTs specially, which is – don't handle them at all.
3435 return (self, &[], &[]);
3438 // First, find at what point do we split between the first and 2nd slice. Easy with
3439 // ptr.align_offset.
3440 let ptr = self.as_ptr();
3441 // SAFETY: See the `align_to_mut` method for the detailed safety comment.
3442 let offset = unsafe { crate::ptr::align_offset(ptr, mem::align_of::<U>()) };
3443 if offset > self.len() {
3446 let (left, rest) = self.split_at(offset);
3447 let (us_len, ts_len) = rest.align_to_offsets::<U>();
3448 // SAFETY: now `rest` is definitely aligned, so `from_raw_parts` below is okay,
3449 // since the caller guarantees that we can transmute `T` to `U` safely.
3453 from_raw_parts(rest.as_ptr() as *const U, us_len),
3454 from_raw_parts(rest.as_ptr().add(rest.len() - ts_len), ts_len),
3460 /// Transmute the slice to a slice of another type, ensuring alignment of the types is
3463 /// This method splits the slice into three distinct slices: prefix, correctly aligned middle
3464 /// slice of a new type, and the suffix slice. The method may make the middle slice the greatest
3465 /// length possible for a given type and input slice, but only your algorithm's performance
3466 /// should depend on that, not its correctness. It is permissible for all of the input data to
3467 /// be returned as the prefix or suffix slice.
3469 /// This method has no purpose when either input element `T` or output element `U` are
3470 /// zero-sized and will return the original slice without splitting anything.
3474 /// This method is essentially a `transmute` with respect to the elements in the returned
3475 /// middle slice, so all the usual caveats pertaining to `transmute::<T, U>` also apply here.
3483 /// let mut bytes: [u8; 7] = [1, 2, 3, 4, 5, 6, 7];
3484 /// let (prefix, shorts, suffix) = bytes.align_to_mut::<u16>();
3485 /// // less_efficient_algorithm_for_bytes(prefix);
3486 /// // more_efficient_algorithm_for_aligned_shorts(shorts);
3487 /// // less_efficient_algorithm_for_bytes(suffix);
3490 #[stable(feature = "slice_align_to", since = "1.30.0")]
3492 pub unsafe fn align_to_mut<U>(&mut self) -> (&mut [T], &mut [U], &mut [T]) {
3493 // Note that most of this function will be constant-evaluated,
3494 if mem::size_of::<U>() == 0 || mem::size_of::<T>() == 0 {
3495 // handle ZSTs specially, which is – don't handle them at all.
3496 return (self, &mut [], &mut []);
3499 // First, find at what point do we split between the first and 2nd slice. Easy with
3500 // ptr.align_offset.
3501 let ptr = self.as_ptr();
3502 // SAFETY: Here we are ensuring we will use aligned pointers for U for the
3503 // rest of the method. This is done by passing a pointer to &[T] with an
3504 // alignment targeted for U.
3505 // `crate::ptr::align_offset` is called with a correctly aligned and
3506 // valid pointer `ptr` (it comes from a reference to `self`) and with
3507 // a size that is a power of two (since it comes from the alignement for U),
3508 // satisfying its safety constraints.
3509 let offset = unsafe { crate::ptr::align_offset(ptr, mem::align_of::<U>()) };
3510 if offset > self.len() {
3511 (self, &mut [], &mut [])
3513 let (left, rest) = self.split_at_mut(offset);
3514 let (us_len, ts_len) = rest.align_to_offsets::<U>();
3515 let rest_len = rest.len();
3516 let mut_ptr = rest.as_mut_ptr();
3517 // We can't use `rest` again after this, that would invalidate its alias `mut_ptr`!
3518 // SAFETY: see comments for `align_to`.
3522 from_raw_parts_mut(mut_ptr as *mut U, us_len),
3523 from_raw_parts_mut(mut_ptr.add(rest_len - ts_len), ts_len),
3529 /// Split a slice into a prefix, a middle of aligned SIMD types, and a suffix.
3531 /// This is a safe wrapper around [`slice::align_to`], so has the same weak
3532 /// postconditions as that method. You're only assured that
3533 /// `self.len() == prefix.len() + middle.len() * LANES + suffix.len()`.
3535 /// Notably, all of the following are possible:
3536 /// - `prefix.len() >= LANES`.
3537 /// - `middle.is_empty()` despite `self.len() >= 3 * LANES`.
3538 /// - `suffix.len() >= LANES`.
3540 /// That said, this is a safe method, so if you're only writing safe code,
3541 /// then this can at most cause incorrect logic, not unsoundness.
3545 /// This will panic if the size of the SIMD type is different from
3546 /// `LANES` times that of the scalar.
3548 /// At the time of writing, the trait restrictions on `Simd<T, LANES>` keeps
3549 /// that from ever happening, as only power-of-two numbers of lanes are
3550 /// supported. It's possible that, in the future, those restrictions might
3551 /// be lifted in a way that would make it possible to see panics from this
3552 /// method for something like `LANES == 3`.
3557 /// #![feature(portable_simd)]
3559 /// let short = &[1, 2, 3];
3560 /// let (prefix, middle, suffix) = short.as_simd::<4>();
3561 /// assert_eq!(middle, []); // Not enough elements for anything in the middle
3563 /// // They might be split in any possible way between prefix and suffix
3564 /// let it = prefix.iter().chain(suffix).copied();
3565 /// assert_eq!(it.collect::<Vec<_>>(), vec![1, 2, 3]);
3567 /// fn basic_simd_sum(x: &[f32]) -> f32 {
3568 /// use std::ops::Add;
3569 /// use std::simd::f32x4;
3570 /// let (prefix, middle, suffix) = x.as_simd();
3571 /// let sums = f32x4::from_array([
3572 /// prefix.iter().copied().sum(),
3575 /// suffix.iter().copied().sum(),
3577 /// let sums = middle.iter().copied().fold(sums, f32x4::add);
3578 /// sums.reduce_sum()
3581 /// let numbers: Vec<f32> = (1..101).map(|x| x as _).collect();
3582 /// assert_eq!(basic_simd_sum(&numbers[1..99]), 4949.0);
3584 #[unstable(feature = "portable_simd", issue = "86656")]
3586 pub fn as_simd<const LANES: usize>(&self) -> (&[T], &[Simd<T, LANES>], &[T])
3588 Simd<T, LANES>: AsRef<[T; LANES]>,
3589 T: simd::SimdElement,
3590 simd::LaneCount<LANES>: simd::SupportedLaneCount,
3592 // These are expected to always match, as vector types are laid out like
3593 // arrays per <https://llvm.org/docs/LangRef.html#vector-type>, but we
3594 // might as well double-check since it'll optimize away anyhow.
3595 assert_eq!(mem::size_of::<Simd<T, LANES>>(), mem::size_of::<[T; LANES]>());
3597 // SAFETY: The simd types have the same layout as arrays, just with
3598 // potentially-higher alignment, so the de-facto transmutes are sound.
3599 unsafe { self.align_to() }
3602 /// Split a slice into a prefix, a middle of aligned SIMD types, and a suffix.
3604 /// This is a safe wrapper around [`slice::align_to_mut`], so has the same weak
3605 /// postconditions as that method. You're only assured that
3606 /// `self.len() == prefix.len() + middle.len() * LANES + suffix.len()`.
3608 /// Notably, all of the following are possible:
3609 /// - `prefix.len() >= LANES`.
3610 /// - `middle.is_empty()` despite `self.len() >= 3 * LANES`.
3611 /// - `suffix.len() >= LANES`.
3613 /// That said, this is a safe method, so if you're only writing safe code,
3614 /// then this can at most cause incorrect logic, not unsoundness.
3616 /// This is the mutable version of [`slice::as_simd`]; see that for examples.
3620 /// This will panic if the size of the SIMD type is different from
3621 /// `LANES` times that of the scalar.
3623 /// At the time of writing, the trait restrictions on `Simd<T, LANES>` keeps
3624 /// that from ever happening, as only power-of-two numbers of lanes are
3625 /// supported. It's possible that, in the future, those restrictions might
3626 /// be lifted in a way that would make it possible to see panics from this
3627 /// method for something like `LANES == 3`.
3628 #[unstable(feature = "portable_simd", issue = "86656")]
3630 pub fn as_simd_mut<const LANES: usize>(&mut self) -> (&mut [T], &mut [Simd<T, LANES>], &mut [T])
3632 Simd<T, LANES>: AsMut<[T; LANES]>,
3633 T: simd::SimdElement,
3634 simd::LaneCount<LANES>: simd::SupportedLaneCount,
3636 // These are expected to always match, as vector types are laid out like
3637 // arrays per <https://llvm.org/docs/LangRef.html#vector-type>, but we
3638 // might as well double-check since it'll optimize away anyhow.
3639 assert_eq!(mem::size_of::<Simd<T, LANES>>(), mem::size_of::<[T; LANES]>());
3641 // SAFETY: The simd types have the same layout as arrays, just with
3642 // potentially-higher alignment, so the de-facto transmutes are sound.
3643 unsafe { self.align_to_mut() }
3646 /// Checks if the elements of this slice are sorted.
3648 /// That is, for each element `a` and its following element `b`, `a <= b` must hold. If the
3649 /// slice yields exactly zero or one element, `true` is returned.
3651 /// Note that if `Self::Item` is only `PartialOrd`, but not `Ord`, the above definition
3652 /// implies that this function returns `false` if any two consecutive items are not
3658 /// #![feature(is_sorted)]
3659 /// let empty: [i32; 0] = [];
3661 /// assert!([1, 2, 2, 9].is_sorted());
3662 /// assert!(![1, 3, 2, 4].is_sorted());
3663 /// assert!([0].is_sorted());
3664 /// assert!(empty.is_sorted());
3665 /// assert!(![0.0, 1.0, f32::NAN].is_sorted());
3668 #[unstable(feature = "is_sorted", reason = "new API", issue = "53485")]
3670 pub fn is_sorted(&self) -> bool
3674 self.is_sorted_by(|a, b| a.partial_cmp(b))
3677 /// Checks if the elements of this slice are sorted using the given comparator function.
3679 /// Instead of using `PartialOrd::partial_cmp`, this function uses the given `compare`
3680 /// function to determine the ordering of two elements. Apart from that, it's equivalent to
3681 /// [`is_sorted`]; see its documentation for more information.
3683 /// [`is_sorted`]: slice::is_sorted
3684 #[unstable(feature = "is_sorted", reason = "new API", issue = "53485")]
3686 pub fn is_sorted_by<F>(&self, mut compare: F) -> bool
3688 F: FnMut(&T, &T) -> Option<Ordering>,
3690 self.iter().is_sorted_by(|a, b| compare(*a, *b))
3693 /// Checks if the elements of this slice are sorted using the given key extraction function.
3695 /// Instead of comparing the slice's elements directly, this function compares the keys of the
3696 /// elements, as determined by `f`. Apart from that, it's equivalent to [`is_sorted`]; see its
3697 /// documentation for more information.
3699 /// [`is_sorted`]: slice::is_sorted
3704 /// #![feature(is_sorted)]
3706 /// assert!(["c", "bb", "aaa"].is_sorted_by_key(|s| s.len()));
3707 /// assert!(![-2i32, -1, 0, 3].is_sorted_by_key(|n| n.abs()));
3710 #[unstable(feature = "is_sorted", reason = "new API", issue = "53485")]
3712 pub fn is_sorted_by_key<F, K>(&self, f: F) -> bool
3717 self.iter().is_sorted_by_key(f)
3720 /// Returns the index of the partition point according to the given predicate
3721 /// (the index of the first element of the second partition).
3723 /// The slice is assumed to be partitioned according to the given predicate.
3724 /// This means that all elements for which the predicate returns true are at the start of the slice
3725 /// and all elements for which the predicate returns false are at the end.
3726 /// For example, [7, 15, 3, 5, 4, 12, 6] is a partitioned under the predicate x % 2 != 0
3727 /// (all odd numbers are at the start, all even at the end).
3729 /// If this slice is not partitioned, the returned result is unspecified and meaningless,
3730 /// as this method performs a kind of binary search.
3732 /// See also [`binary_search`], [`binary_search_by`], and [`binary_search_by_key`].
3734 /// [`binary_search`]: slice::binary_search
3735 /// [`binary_search_by`]: slice::binary_search_by
3736 /// [`binary_search_by_key`]: slice::binary_search_by_key
3741 /// let v = [1, 2, 3, 3, 5, 6, 7];
3742 /// let i = v.partition_point(|&x| x < 5);
3744 /// assert_eq!(i, 4);
3745 /// assert!(v[..i].iter().all(|&x| x < 5));
3746 /// assert!(v[i..].iter().all(|&x| !(x < 5)));
3748 #[stable(feature = "partition_point", since = "1.52.0")]
3750 pub fn partition_point<P>(&self, mut pred: P) -> usize
3752 P: FnMut(&T) -> bool,
3754 self.binary_search_by(|x| if pred(x) { Less } else { Greater }).unwrap_or_else(|i| i)
3757 /// Removes the subslice corresponding to the given range
3758 /// and returns a reference to it.
3760 /// Returns `None` and does not modify the slice if the given
3761 /// range is out of bounds.
3763 /// Note that this method only accepts one-sided ranges such as
3764 /// `2..` or `..6`, but not `2..6`.
3768 /// Taking the first three elements of a slice:
3771 /// #![feature(slice_take)]
3773 /// let mut slice: &[_] = &['a', 'b', 'c', 'd'];
3774 /// let mut first_three = slice.take(..3).unwrap();
3776 /// assert_eq!(slice, &['d']);
3777 /// assert_eq!(first_three, &['a', 'b', 'c']);
3780 /// Taking the last two elements of a slice:
3783 /// #![feature(slice_take)]
3785 /// let mut slice: &[_] = &['a', 'b', 'c', 'd'];
3786 /// let mut tail = slice.take(2..).unwrap();
3788 /// assert_eq!(slice, &['a', 'b']);
3789 /// assert_eq!(tail, &['c', 'd']);
3792 /// Getting `None` when `range` is out of bounds:
3795 /// #![feature(slice_take)]
3797 /// let mut slice: &[_] = &['a', 'b', 'c', 'd'];
3799 /// assert_eq!(None, slice.take(5..));
3800 /// assert_eq!(None, slice.take(..5));
3801 /// assert_eq!(None, slice.take(..=4));
3802 /// let expected: &[char] = &['a', 'b', 'c', 'd'];
3803 /// assert_eq!(Some(expected), slice.take(..4));
3806 #[must_use = "method does not modify the slice if the range is out of bounds"]
3807 #[unstable(feature = "slice_take", issue = "62280")]
3808 pub fn take<'a, R: OneSidedRange<usize>>(self: &mut &'a Self, range: R) -> Option<&'a Self> {
3809 let (direction, split_index) = split_point_of(range)?;
3810 if split_index > self.len() {
3813 let (front, back) = self.split_at(split_index);
3815 Direction::Front => {
3819 Direction::Back => {
3826 /// Removes the subslice corresponding to the given range
3827 /// and returns a mutable reference to it.
3829 /// Returns `None` and does not modify the slice if the given
3830 /// range is out of bounds.
3832 /// Note that this method only accepts one-sided ranges such as
3833 /// `2..` or `..6`, but not `2..6`.
3837 /// Taking the first three elements of a slice:
3840 /// #![feature(slice_take)]
3842 /// let mut slice: &mut [_] = &mut ['a', 'b', 'c', 'd'];
3843 /// let mut first_three = slice.take_mut(..3).unwrap();
3845 /// assert_eq!(slice, &mut ['d']);
3846 /// assert_eq!(first_three, &mut ['a', 'b', 'c']);
3849 /// Taking the last two elements of a slice:
3852 /// #![feature(slice_take)]
3854 /// let mut slice: &mut [_] = &mut ['a', 'b', 'c', 'd'];
3855 /// let mut tail = slice.take_mut(2..).unwrap();
3857 /// assert_eq!(slice, &mut ['a', 'b']);
3858 /// assert_eq!(tail, &mut ['c', 'd']);
3861 /// Getting `None` when `range` is out of bounds:
3864 /// #![feature(slice_take)]
3866 /// let mut slice: &mut [_] = &mut ['a', 'b', 'c', 'd'];
3868 /// assert_eq!(None, slice.take_mut(5..));
3869 /// assert_eq!(None, slice.take_mut(..5));
3870 /// assert_eq!(None, slice.take_mut(..=4));
3871 /// let expected: &mut [_] = &mut ['a', 'b', 'c', 'd'];
3872 /// assert_eq!(Some(expected), slice.take_mut(..4));
3875 #[must_use = "method does not modify the slice if the range is out of bounds"]
3876 #[unstable(feature = "slice_take", issue = "62280")]
3877 pub fn take_mut<'a, R: OneSidedRange<usize>>(
3878 self: &mut &'a mut Self,
3880 ) -> Option<&'a mut Self> {
3881 let (direction, split_index) = split_point_of(range)?;
3882 if split_index > self.len() {
3885 let (front, back) = mem::take(self).split_at_mut(split_index);
3887 Direction::Front => {
3891 Direction::Back => {
3898 /// Removes the first element of the slice and returns a reference
3901 /// Returns `None` if the slice is empty.
3906 /// #![feature(slice_take)]
3908 /// let mut slice: &[_] = &['a', 'b', 'c'];
3909 /// let first = slice.take_first().unwrap();
3911 /// assert_eq!(slice, &['b', 'c']);
3912 /// assert_eq!(first, &'a');
3915 #[unstable(feature = "slice_take", issue = "62280")]
3916 pub fn take_first<'a>(self: &mut &'a Self) -> Option<&'a T> {
3917 let (first, rem) = self.split_first()?;
3922 /// Removes the first element of the slice and returns a mutable
3923 /// reference to it.
3925 /// Returns `None` if the slice is empty.
3930 /// #![feature(slice_take)]
3932 /// let mut slice: &mut [_] = &mut ['a', 'b', 'c'];
3933 /// let first = slice.take_first_mut().unwrap();
3936 /// assert_eq!(slice, &['b', 'c']);
3937 /// assert_eq!(first, &'d');
3940 #[unstable(feature = "slice_take", issue = "62280")]
3941 pub fn take_first_mut<'a>(self: &mut &'a mut Self) -> Option<&'a mut T> {
3942 let (first, rem) = mem::take(self).split_first_mut()?;
3947 /// Removes the last element of the slice and returns a reference
3950 /// Returns `None` if the slice is empty.
3955 /// #![feature(slice_take)]
3957 /// let mut slice: &[_] = &['a', 'b', 'c'];
3958 /// let last = slice.take_last().unwrap();
3960 /// assert_eq!(slice, &['a', 'b']);
3961 /// assert_eq!(last, &'c');
3964 #[unstable(feature = "slice_take", issue = "62280")]
3965 pub fn take_last<'a>(self: &mut &'a Self) -> Option<&'a T> {
3966 let (last, rem) = self.split_last()?;
3971 /// Removes the last element of the slice and returns a mutable
3972 /// reference to it.
3974 /// Returns `None` if the slice is empty.
3979 /// #![feature(slice_take)]
3981 /// let mut slice: &mut [_] = &mut ['a', 'b', 'c'];
3982 /// let last = slice.take_last_mut().unwrap();
3985 /// assert_eq!(slice, &['a', 'b']);
3986 /// assert_eq!(last, &'d');
3989 #[unstable(feature = "slice_take", issue = "62280")]
3990 pub fn take_last_mut<'a>(self: &mut &'a mut Self) -> Option<&'a mut T> {
3991 let (last, rem) = mem::take(self).split_last_mut()?;
3997 trait CloneFromSpec<T> {
3998 fn spec_clone_from(&mut self, src: &[T]);
4001 impl<T> CloneFromSpec<T> for [T]
4006 default fn spec_clone_from(&mut self, src: &[T]) {
4007 assert!(self.len() == src.len(), "destination and source slices have different lengths");
4008 // NOTE: We need to explicitly slice them to the same length
4009 // to make it easier for the optimizer to elide bounds checking.
4010 // But since it can't be relied on we also have an explicit specialization for T: Copy.
4011 let len = self.len();
4012 let src = &src[..len];
4014 self[i].clone_from(&src[i]);
4019 impl<T> CloneFromSpec<T> for [T]
4024 fn spec_clone_from(&mut self, src: &[T]) {
4025 self.copy_from_slice(src);
4029 #[stable(feature = "rust1", since = "1.0.0")]
4030 #[rustc_const_unstable(feature = "const_default_impls", issue = "87864")]
4031 impl<T> const Default for &[T] {
4032 /// Creates an empty slice.
4033 fn default() -> Self {
4038 #[stable(feature = "mut_slice_default", since = "1.5.0")]
4039 #[rustc_const_unstable(feature = "const_default_impls", issue = "87864")]
4040 impl<T> const Default for &mut [T] {
4041 /// Creates a mutable empty slice.
4042 fn default() -> Self {
4047 #[unstable(feature = "slice_pattern", reason = "stopgap trait for slice patterns", issue = "56345")]
4048 /// Patterns in slices - currently, only used by `strip_prefix` and `strip_suffix`. At a future
4049 /// point, we hope to generalise `core::str::Pattern` (which at the time of writing is limited to
4050 /// `str`) to slices, and then this trait will be replaced or abolished.
4051 pub trait SlicePattern {
4052 /// The element type of the slice being matched on.
4055 /// Currently, the consumers of `SlicePattern` need a slice.
4056 fn as_slice(&self) -> &[Self::Item];
4059 #[stable(feature = "slice_strip", since = "1.51.0")]
4060 impl<T> SlicePattern for [T] {
4064 fn as_slice(&self) -> &[Self::Item] {
4069 #[stable(feature = "slice_strip", since = "1.51.0")]
4070 impl<T, const N: usize> SlicePattern for [T; N] {
4074 fn as_slice(&self) -> &[Self::Item] {