linux-x86/1.55.0/src/stdlibs/library/core/src/array/mod.rs - platform/prebuilts/rust - Git at Google

 //! Helper functions and types for fixed-length arrays.
 //!
 //! *[See also the array primitive type](array).*

 #![stable(feature = "core_array", since = "1.36.0")]

 use crate::borrow::{Borrow, BorrowMut};
 use crate::cmp::Ordering;
 use crate::convert::{Infallible, TryFrom};
 use crate::fmt;
 use crate::hash::{self, Hash};
 use crate::iter::TrustedLen;
 use crate::mem::{self, MaybeUninit};
 use crate::ops::{Index, IndexMut};
 use crate::slice::{Iter, IterMut};

 mod equality;
 mod iter;

 #[stable(feature = "array_value_iter", since = "1.51.0")]
 pub use iter::IntoIter;

 /// Converts a reference to `T` into a reference to an array of length 1 (without copying).
 #[stable(feature = "array_from_ref", since = "1.53.0")]
 pub fn from_ref<T>(s: &T) -> &[T; 1] {
     // SAFETY: Converting `&T` to `&[T; 1]` is sound.
     unsafe { &*(s as *const T).cast::<[T; 1]>() }
 }

 /// Converts a mutable reference to `T` into a mutable reference to an array of length 1 (without copying).
 #[stable(feature = "array_from_ref", since = "1.53.0")]
 pub fn from_mut<T>(s: &mut T) -> &mut [T; 1] {
     // SAFETY: Converting `&mut T` to `&mut [T; 1]` is sound.
     unsafe { &mut *(s as *mut T).cast::<[T; 1]>() }
 }

 /// The error type returned when a conversion from a slice to an array fails.
 #[stable(feature = "try_from", since = "1.34.0")]
 #[derive(Debug, Copy, Clone)]
 pub struct TryFromSliceError(());

 #[stable(feature = "core_array", since = "1.36.0")]
 impl fmt::Display for TryFromSliceError {
     #[inline]
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         fmt::Display::fmt(self.__description(), f)
     }
 }

 impl TryFromSliceError {
     #[unstable(
         feature = "array_error_internals",
         reason = "available through Error trait and this method should not \
                      be exposed publicly",
         issue = "none"
     )]
     #[inline]
     #[doc(hidden)]
     pub fn __description(&self) -> &str {
         "could not convert slice to array"
     }
 }

 #[stable(feature = "try_from_slice_error", since = "1.36.0")]
 impl From<Infallible> for TryFromSliceError {
     fn from(x: Infallible) -> TryFromSliceError {
         match x {}
     }
 }

 #[stable(feature = "rust1", since = "1.0.0")]
 impl<T, const N: usize> AsRef<[T]> for [T; N] {
     #[inline]
     fn as_ref(&self) -> &[T] {
         &self[..]
     }
 }

 #[stable(feature = "rust1", since = "1.0.0")]
 impl<T, const N: usize> AsMut<[T]> for [T; N] {
     #[inline]
     fn as_mut(&mut self) -> &mut [T] {
         &mut self[..]
     }
 }

 #[stable(feature = "array_borrow", since = "1.4.0")]
 impl<T, const N: usize> Borrow<[T]> for [T; N] {
     fn borrow(&self) -> &[T] {
         self
     }
 }

 #[stable(feature = "array_borrow", since = "1.4.0")]
 impl<T, const N: usize> BorrowMut<[T]> for [T; N] {
     fn borrow_mut(&mut self) -> &mut [T] {
         self
     }
 }

 #[stable(feature = "try_from", since = "1.34.0")]
 impl<T, const N: usize> TryFrom<&[T]> for [T; N]
 where
     T: Copy,
 {
     type Error = TryFromSliceError;

     fn try_from(slice: &[T]) -> Result<[T; N], TryFromSliceError> {
         <&Self>::try_from(slice).map(|r| *r)
     }
 }

 #[stable(feature = "try_from", since = "1.34.0")]
 impl<'a, T, const N: usize> TryFrom<&'a [T]> for &'a [T; N] {
     type Error = TryFromSliceError;

     fn try_from(slice: &[T]) -> Result<&[T; N], TryFromSliceError> {
         if slice.len() == N {
             let ptr = slice.as_ptr() as *const [T; N];
             // SAFETY: ok because we just checked that the length fits
             unsafe { Ok(&*ptr) }
         } else {
             Err(TryFromSliceError(()))
         }
     }
 }

 #[stable(feature = "try_from", since = "1.34.0")]
 impl<'a, T, const N: usize> TryFrom<&'a mut [T]> for &'a mut [T; N] {
     type Error = TryFromSliceError;

     fn try_from(slice: &mut [T]) -> Result<&mut [T; N], TryFromSliceError> {
         if slice.len() == N {
             let ptr = slice.as_mut_ptr() as *mut [T; N];
             // SAFETY: ok because we just checked that the length fits
             unsafe { Ok(&mut *ptr) }
         } else {
             Err(TryFromSliceError(()))
         }
     }
 }

 /// The hash of an array is the same as that of the corresponding slice,
 /// as required by the `Borrow` implementation.
 ///
 /// ```
 /// #![feature(build_hasher_simple_hash_one)]
 /// use std::hash::BuildHasher;
 ///
 /// let b = std::collections::hash_map::RandomState::new();
 /// let a: [u8; 3] = [0xa8, 0x3c, 0x09];
 /// let s: &[u8] = &[0xa8, 0x3c, 0x09];
 /// assert_eq!(b.hash_one(a), b.hash_one(s));
 /// ```
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<T: Hash, const N: usize> Hash for [T; N] {
     fn hash<H: hash::Hasher>(&self, state: &mut H) {
         Hash::hash(&self[..], state)
     }
 }

 #[stable(feature = "rust1", since = "1.0.0")]
 impl<T: fmt::Debug, const N: usize> fmt::Debug for [T; N] {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         fmt::Debug::fmt(&&self[..], f)
     }
 }

 // Note: the `#[rustc_skip_array_during_method_dispatch]` on `trait IntoIterator`
 // hides this implementation from explicit `.into_iter()` calls on editions < 2021,
 // so those calls will still resolve to the slice implementation, by reference.
 #[stable(feature = "array_into_iter_impl", since = "1.53.0")]
 impl<T, const N: usize> IntoIterator for [T; N] {
     type Item = T;
     type IntoIter = IntoIter<T, N>;

     /// Creates a consuming iterator, that is, one that moves each value out of
     /// the array (from start to end). The array cannot be used after calling
     /// this unless `T` implements `Copy`, so the whole array is copied.
     ///
     /// Arrays have special behavior when calling `.into_iter()` prior to the
     /// 2021 edition -- see the [array] Editions section for more information.
     ///
     /// [array]: prim@array
     fn into_iter(self) -> Self::IntoIter {
         IntoIter::new(self)
     }
 }

 #[stable(feature = "rust1", since = "1.0.0")]
 impl<'a, T, const N: usize> IntoIterator for &'a [T; N] {
     type Item = &'a T;
     type IntoIter = Iter<'a, T>;

     fn into_iter(self) -> Iter<'a, T> {
         self.iter()
     }
 }

 #[stable(feature = "rust1", since = "1.0.0")]
 impl<'a, T, const N: usize> IntoIterator for &'a mut [T; N] {
     type Item = &'a mut T;
     type IntoIter = IterMut<'a, T>;

     fn into_iter(self) -> IterMut<'a, T> {
         self.iter_mut()
     }
 }

 #[stable(feature = "index_trait_on_arrays", since = "1.50.0")]
 impl<T, I, const N: usize> Index<I> for [T; N]
 where
     [T]: Index<I>,
 {
     type Output = <[T] as Index<I>>::Output;

     #[inline]
     fn index(&self, index: I) -> &Self::Output {
         Index::index(self as &[T], index)
     }
 }

 #[stable(feature = "index_trait_on_arrays", since = "1.50.0")]
 impl<T, I, const N: usize> IndexMut<I> for [T; N]
 where
     [T]: IndexMut<I>,
 {
     #[inline]
     fn index_mut(&mut self, index: I) -> &mut Self::Output {
         IndexMut::index_mut(self as &mut [T], index)
     }
 }

 #[stable(feature = "rust1", since = "1.0.0")]
 impl<T: PartialOrd, const N: usize> PartialOrd for [T; N] {
     #[inline]
     fn partial_cmp(&self, other: &[T; N]) -> Option<Ordering> {
         PartialOrd::partial_cmp(&&self[..], &&other[..])
     }
     #[inline]
     fn lt(&self, other: &[T; N]) -> bool {
         PartialOrd::lt(&&self[..], &&other[..])
     }
     #[inline]
     fn le(&self, other: &[T; N]) -> bool {
         PartialOrd::le(&&self[..], &&other[..])
     }
     #[inline]
     fn ge(&self, other: &[T; N]) -> bool {
         PartialOrd::ge(&&self[..], &&other[..])
     }
     #[inline]
     fn gt(&self, other: &[T; N]) -> bool {
         PartialOrd::gt(&&self[..], &&other[..])
     }
 }

 /// Implements comparison of arrays [lexicographically](Ord#lexicographical-comparison).
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<T: Ord, const N: usize> Ord for [T; N] {
     #[inline]
     fn cmp(&self, other: &[T; N]) -> Ordering {
         Ord::cmp(&&self[..], &&other[..])
     }
 }

 // The Default impls cannot be done with const generics because `[T; 0]` doesn't
 // require Default to be implemented, and having different impl blocks for
 // different numbers isn't supported yet.

 macro_rules! array_impl_default {
     {$n:expr, $t:ident $($ts:ident)*} => {
         #[stable(since = "1.4.0", feature = "array_default")]
         impl<T> Default for [T; $n] where T: Default {
             fn default() -> [T; $n] {
                 [$t::default(), $($ts::default()),*]
             }
         }
         array_impl_default!{($n - 1), $($ts)*}
     };
     {$n:expr,} => {
         #[stable(since = "1.4.0", feature = "array_default")]
         impl<T> Default for [T; $n] {
             fn default() -> [T; $n] { [] }
         }
     };
 }

 array_impl_default! {32, T T T T T T T T T T T T T T T T T T T T T T T T T T T T T T T T}

 #[lang = "array"]
 impl<T, const N: usize> [T; N] {
     /// Returns an array of the same size as `self`, with function `f` applied to each element
     /// in order.
     ///
     /// # Examples
     ///
     /// ```
     /// let x = [1, 2, 3];
     /// let y = x.map(|v| v + 1);
     /// assert_eq!(y, [2, 3, 4]);
     ///
     /// let x = [1, 2, 3];
     /// let mut temp = 0;
     /// let y = x.map(|v| { temp += 1; v * temp });
     /// assert_eq!(y, [1, 4, 9]);
     ///
     /// let x = ["Ferris", "Bueller's", "Day", "Off"];
     /// let y = x.map(|v| v.len());
     /// assert_eq!(y, [6, 9, 3, 3]);
     /// ```
     #[stable(feature = "array_map", since = "1.55.0")]
     pub fn map<F, U>(self, f: F) -> [U; N]
     where
         F: FnMut(T) -> U,
     {
         // SAFETY: we know for certain that this iterator will yield exactly `N`
         // items.
         unsafe { collect_into_array_unchecked(&mut IntoIterator::into_iter(self).map(f)) }
     }

     /// 'Zips up' two arrays into a single array of pairs.
     ///
     /// `zip()` returns a new array where every element is a tuple where the
     /// first element comes from the first array, and the second element comes
     /// from the second array. In other words, it zips two arrays together,
     /// into a single one.
     ///
     /// # Examples
     ///
     /// ```
     /// #![feature(array_zip)]
     /// let x = [1, 2, 3];
     /// let y = [4, 5, 6];
     /// let z = x.zip(y);
     /// assert_eq!(z, [(1, 4), (2, 5), (3, 6)]);
     /// ```
     #[unstable(feature = "array_zip", issue = "80094")]
     pub fn zip<U>(self, rhs: [U; N]) -> [(T, U); N] {
         let mut iter = IntoIterator::into_iter(self).zip(rhs);

         // SAFETY: we know for certain that this iterator will yield exactly `N`
         // items.
         unsafe { collect_into_array_unchecked(&mut iter) }
     }

     /// Returns a slice containing the entire array. Equivalent to `&s[..]`.
     #[unstable(feature = "array_methods", issue = "76118")]
     pub fn as_slice(&self) -> &[T] {
         self
     }

     /// Returns a mutable slice containing the entire array. Equivalent to
     /// `&mut s[..]`.
     #[unstable(feature = "array_methods", issue = "76118")]
     pub fn as_mut_slice(&mut self) -> &mut [T] {
         self
     }

     /// Borrows each element and returns an array of references with the same
     /// size as `self`.
     ///
     ///
     /// # Example
     ///
     /// ```
     /// #![feature(array_methods)]
     ///
     /// let floats = [3.1, 2.7, -1.0];
     /// let float_refs: [&f64; 3] = floats.each_ref();
     /// assert_eq!(float_refs, [&3.1, &2.7, &-1.0]);
     /// ```
     ///
     /// This method is particularly useful if combined with other methods, like
     /// [`map`](#method.map). This way, you can avoid moving the original
     /// array if its elements are not `Copy`.
     ///
     /// ```
     /// #![feature(array_methods)]
     ///
     /// let strings = ["Ferris".to_string(), "♥".to_string(), "Rust".to_string()];
     /// let is_ascii = strings.each_ref().map(|s| s.is_ascii());
     /// assert_eq!(is_ascii, [true, false, true]);
     ///
     /// // We can still access the original array: it has not been moved.
     /// assert_eq!(strings.len(), 3);
     /// ```
     #[unstable(feature = "array_methods", issue = "76118")]
     pub fn each_ref(&self) -> [&T; N] {
         // SAFETY: we know for certain that this iterator will yield exactly `N`
         // items.
         unsafe { collect_into_array_unchecked(&mut self.iter()) }
     }

     /// Borrows each element mutably and returns an array of mutable references
     /// with the same size as `self`.
     ///
     ///
     /// # Example
     ///
     /// ```
     /// #![feature(array_methods)]
     ///
     /// let mut floats = [3.1, 2.7, -1.0];
     /// let float_refs: [&mut f64; 3] = floats.each_mut();
     /// *float_refs[0] = 0.0;
     /// assert_eq!(float_refs, [&mut 0.0, &mut 2.7, &mut -1.0]);
     /// assert_eq!(floats, [0.0, 2.7, -1.0]);
     /// ```
     #[unstable(feature = "array_methods", issue = "76118")]
     pub fn each_mut(&mut self) -> [&mut T; N] {
         // SAFETY: we know for certain that this iterator will yield exactly `N`
         // items.
         unsafe { collect_into_array_unchecked(&mut self.iter_mut()) }
     }
 }

 /// Pulls `N` items from `iter` and returns them as an array. If the iterator
 /// yields fewer than `N` items, this function exhibits undefined behavior.
 ///
 /// See [`collect_into_array`] for more information.
 ///
 ///
 /// # Safety
 ///
 /// It is up to the caller to guarantee that `iter` yields at least `N` items.
 /// Violating this condition causes undefined behavior.
 unsafe fn collect_into_array_unchecked<I, const N: usize>(iter: &mut I) -> [I::Item; N]
 where
     // Note: `TrustedLen` here is somewhat of an experiment. This is just an
     // internal function, so feel free to remove if this bound turns out to be a
     // bad idea. In that case, remember to also remove the lower bound
     // `debug_assert!` below!
     I: Iterator + TrustedLen,
 {
     debug_assert!(N <= iter.size_hint().1.unwrap_or(usize::MAX));
     debug_assert!(N <= iter.size_hint().0);

     match collect_into_array(iter) {
         Some(array) => array,
         // SAFETY: covered by the function contract.
         None => unsafe { crate::hint::unreachable_unchecked() },
     }
 }

 /// Pulls `N` items from `iter` and returns them as an array. If the iterator
 /// yields fewer than `N` items, `None` is returned and all already yielded
 /// items are dropped.
 ///
 /// Since the iterator is passed as a mutable reference and this function calls
 /// `next` at most `N` times, the iterator can still be used afterwards to
 /// retrieve the remaining items.
 ///
 /// If `iter.next()` panicks, all items already yielded by the iterator are
 /// dropped.
 fn collect_into_array<I, const N: usize>(iter: &mut I) -> Option<[I::Item; N]>
 where
     I: Iterator,
 {
     if N == 0 {
         // SAFETY: An empty array is always inhabited and has no validity invariants.
         return unsafe { Some(mem::zeroed()) };
     }

     struct Guard<T, const N: usize> {
         ptr: *mut T,
         initialized: usize,
     }

     impl<T, const N: usize> Drop for Guard<T, N> {
         fn drop(&mut self) {
             debug_assert!(self.initialized <= N);

             let initialized_part = crate::ptr::slice_from_raw_parts_mut(self.ptr, self.initialized);

             // SAFETY: this raw slice will contain only initialized objects.
             unsafe {
                 crate::ptr::drop_in_place(initialized_part);
             }
         }
     }

     let mut array = MaybeUninit::uninit_array::<N>();
     let mut guard: Guard<_, N> =
         Guard { ptr: MaybeUninit::slice_as_mut_ptr(&mut array), initialized: 0 };

     while let Some(item) = iter.next() {
         // SAFETY: `guard.initialized` starts at 0, is increased by one in the
         // loop and the loop is aborted once it reaches N (which is
         // `array.len()`).
         unsafe {
             array.get_unchecked_mut(guard.initialized).write(item);
         }
         guard.initialized += 1;

         // Check if the whole array was initialized.
         if guard.initialized == N {
             mem::forget(guard);

             // SAFETY: the condition above asserts that all elements are
             // initialized.
             let out = unsafe { MaybeUninit::array_assume_init(array) };
             return Some(out);
         }
     }

     // This is only reached if the iterator is exhausted before
     // `guard.initialized` reaches `N`. Also note that `guard` is dropped here,
     // dropping all already initialized elements.
     None
 }
	//! Helper functions and types for fixed-length arrays.
	//!
	//! [See also the array primitive type](array).

	#![stable(feature = "core_array", since = "1.36.0")]

	use crate::borrow::{Borrow, BorrowMut};
	use crate::cmp::Ordering;
	use crate::convert::{Infallible, TryFrom};
	use crate::fmt;
	use crate::hash::{self, Hash};
	use crate::iter::TrustedLen;
	use crate::mem::{self, MaybeUninit};
	use crate::ops::{Index, IndexMut};
	use crate::slice::{Iter, IterMut};

	mod equality;
	mod iter;

	#[stable(feature = "array_value_iter", since = "1.51.0")]
	pub use iter::IntoIter;

	/// Converts a reference to `T` into a reference to an array of length 1 (without copying).
	#[stable(feature = "array_from_ref", since = "1.53.0")]
	pub fn from_ref<T>(s: &T) -> &[T; 1] {
	// SAFETY: Converting `&T` to `&[T; 1]` is sound.
	unsafe { &(s as const T).cast::<[T; 1]>() }
	}

	/// Converts a mutable reference to `T` into a mutable reference to an array of length 1 (without copying).
	#[stable(feature = "array_from_ref", since = "1.53.0")]
	pub fn from_mut<T>(s: &mut T) -> &mut [T; 1] {
	// SAFETY: Converting `&mut T` to `&mut [T; 1]` is sound.
	unsafe { &mut (s as mut T).cast::<[T; 1]>() }
	}

	/// The error type returned when a conversion from a slice to an array fails.
	#[stable(feature = "try_from", since = "1.34.0")]
	#[derive(Debug, Copy, Clone)]
	pub struct TryFromSliceError(());

	#[stable(feature = "core_array", since = "1.36.0")]
	impl fmt::Display for TryFromSliceError {
	#[inline]
	fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
	fmt::Display::fmt(self.__description(), f)
	}
	}

	impl TryFromSliceError {
	#[unstable(
	feature = "array_error_internals",
	reason = "available through Error trait and this method should not \
	be exposed publicly",
	issue = "none"
	)]
	#[inline]
	#[doc(hidden)]
	pub fn __description(&self) -> &str {
	"could not convert slice to array"
	}
	}

	#[stable(feature = "try_from_slice_error", since = "1.36.0")]
	impl From<Infallible> for TryFromSliceError {
	fn from(x: Infallible) -> TryFromSliceError {
	match x {}
	}
	}

	#[stable(feature = "rust1", since = "1.0.0")]
	impl<T, const N: usize> AsRef<[T]> for [T; N] {
	#[inline]
	fn as_ref(&self) -> &[T] {
	&self[..]
	}
	}

	#[stable(feature = "rust1", since = "1.0.0")]
	impl<T, const N: usize> AsMut<[T]> for [T; N] {
	#[inline]
	fn as_mut(&mut self) -> &mut [T] {
	&mut self[..]
	}
	}

	#[stable(feature = "array_borrow", since = "1.4.0")]
	impl<T, const N: usize> Borrow<[T]> for [T; N] {
	fn borrow(&self) -> &[T] {
	self
	}
	}

	#[stable(feature = "array_borrow", since = "1.4.0")]
	impl<T, const N: usize> BorrowMut<[T]> for [T; N] {
	fn borrow_mut(&mut self) -> &mut [T] {
	self
	}
	}

	#[stable(feature = "try_from", since = "1.34.0")]
	impl<T, const N: usize> TryFrom<&[T]> for [T; N]
	where
	T: Copy,
	{
	type Error = TryFromSliceError;

	fn try_from(slice: &[T]) -> Result<[T; N], TryFromSliceError> {
	<&Self>::try_from(slice).map(\|r\| *r)
	}
	}

	#[stable(feature = "try_from", since = "1.34.0")]
	impl<'a, T, const N: usize> TryFrom<&'a [T]> for &'a [T; N] {
	type Error = TryFromSliceError;

	fn try_from(slice: &[T]) -> Result<&[T; N], TryFromSliceError> {
	if slice.len() == N {
	let ptr = slice.as_ptr() as *const [T; N];
	// SAFETY: ok because we just checked that the length fits
	unsafe { Ok(&*ptr) }
	} else {
	Err(TryFromSliceError(()))
	}
	}
	}

	#[stable(feature = "try_from", since = "1.34.0")]
	impl<'a, T, const N: usize> TryFrom<&'a mut [T]> for &'a mut [T; N] {
	type Error = TryFromSliceError;

	fn try_from(slice: &mut [T]) -> Result<&mut [T; N], TryFromSliceError> {
	if slice.len() == N {
	let ptr = slice.as_mut_ptr() as *mut [T; N];
	// SAFETY: ok because we just checked that the length fits
	unsafe { Ok(&mut *ptr) }
	} else {
	Err(TryFromSliceError(()))
	}
	}
	}

	/// The hash of an array is the same as that of the corresponding slice,
	/// as required by the `Borrow` implementation.
	///
	/// ```
	/// #![feature(build_hasher_simple_hash_one)]
	/// use std::hash::BuildHasher;
	///
	/// let b = std::collections::hash_map::RandomState::new();
	/// let a: [u8; 3] = [0xa8, 0x3c, 0x09];
	/// let s: &[u8] = &[0xa8, 0x3c, 0x09];
	/// assert_eq!(b.hash_one(a), b.hash_one(s));
	/// ```
	#[stable(feature = "rust1", since = "1.0.0")]
	impl<T: Hash, const N: usize> Hash for [T; N] {
	fn hash<H: hash::Hasher>(&self, state: &mut H) {
	Hash::hash(&self[..], state)
	}
	}

	#[stable(feature = "rust1", since = "1.0.0")]
	impl<T: fmt::Debug, const N: usize> fmt::Debug for [T; N] {
	fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
	fmt::Debug::fmt(&&self[..], f)
	}
	}

	// Note: the `#[rustc_skip_array_during_method_dispatch]` on `trait IntoIterator`
	// hides this implementation from explicit `.into_iter()` calls on editions < 2021,
	// so those calls will still resolve to the slice implementation, by reference.
	#[stable(feature = "array_into_iter_impl", since = "1.53.0")]
	impl<T, const N: usize> IntoIterator for [T; N] {
	type Item = T;
	type IntoIter = IntoIter<T, N>;

	/// Creates a consuming iterator, that is, one that moves each value out of
	/// the array (from start to end). The array cannot be used after calling
	/// this unless `T` implements `Copy`, so the whole array is copied.
	///
	/// Arrays have special behavior when calling `.into_iter()` prior to the
	/// 2021 edition -- see the [array] Editions section for more information.
	///
	/// [array]: prim@array
	fn into_iter(self) -> Self::IntoIter {
	IntoIter::new(self)
	}
	}

	#[stable(feature = "rust1", since = "1.0.0")]
	impl<'a, T, const N: usize> IntoIterator for &'a [T; N] {
	type Item = &'a T;
	type IntoIter = Iter<'a, T>;

	fn into_iter(self) -> Iter<'a, T> {
	self.iter()
	}
	}

	#[stable(feature = "rust1", since = "1.0.0")]
	impl<'a, T, const N: usize> IntoIterator for &'a mut [T; N] {
	type Item = &'a mut T;
	type IntoIter = IterMut<'a, T>;

	fn into_iter(self) -> IterMut<'a, T> {
	self.iter_mut()
	}
	}

	#[stable(feature = "index_trait_on_arrays", since = "1.50.0")]
	impl<T, I, const N: usize> Index<I> for [T; N]
	where
	[T]: Index<I>,
	{
	type Output = <[T] as Index<I>>::Output;

	#[inline]
	fn index(&self, index: I) -> &Self::Output {
	Index::index(self as &[T], index)
	}
	}

	#[stable(feature = "index_trait_on_arrays", since = "1.50.0")]
	impl<T, I, const N: usize> IndexMut<I> for [T; N]
	where
	[T]: IndexMut<I>,
	{
	#[inline]
	fn index_mut(&mut self, index: I) -> &mut Self::Output {
	IndexMut::index_mut(self as &mut [T], index)
	}
	}

	#[stable(feature = "rust1", since = "1.0.0")]
	impl<T: PartialOrd, const N: usize> PartialOrd for [T; N] {
	#[inline]
	fn partial_cmp(&self, other: &[T; N]) -> Option<Ordering> {
	PartialOrd::partial_cmp(&&self[..], &&other[..])
	}
	#[inline]
	fn lt(&self, other: &[T; N]) -> bool {
	PartialOrd::lt(&&self[..], &&other[..])
	}
	#[inline]
	fn le(&self, other: &[T; N]) -> bool {
	PartialOrd::le(&&self[..], &&other[..])
	}
	#[inline]
	fn ge(&self, other: &[T; N]) -> bool {
	PartialOrd::ge(&&self[..], &&other[..])
	}
	#[inline]
	fn gt(&self, other: &[T; N]) -> bool {
	PartialOrd::gt(&&self[..], &&other[..])
	}
	}

	/// Implements comparison of arrays [lexicographically](Ord#lexicographical-comparison).
	#[stable(feature = "rust1", since = "1.0.0")]
	impl<T: Ord, const N: usize> Ord for [T; N] {
	#[inline]
	fn cmp(&self, other: &[T; N]) -> Ordering {
	Ord::cmp(&&self[..], &&other[..])
	}
	}

	// The Default impls cannot be done with const generics because `[T; 0]` doesn't
	// require Default to be implemented, and having different impl blocks for
	// different numbers isn't supported yet.

	macro_rules! array_impl_default {
	{$n:expr, $t:ident $($ts:ident)*} => {
	#[stable(since = "1.4.0", feature = "array_default")]
	impl<T> Default for [T; $n] where T: Default {
	fn default() -> [T; $n] {
	[$t::default(), $($ts::default()),*]
	}
	}
	array_impl_default!{($n - 1), $($ts)*}
	};
	{$n:expr,} => {
	#[stable(since = "1.4.0", feature = "array_default")]
	impl<T> Default for [T; $n] {
	fn default() -> [T; $n] { [] }
	}
	};
	}

	array_impl_default! {32, T T T T T T T T T T T T T T T T T T T T T T T T T T T T T T T T}

	#[lang = "array"]
	impl<T, const N: usize> [T; N] {
	/// Returns an array of the same size as `self`, with function `f` applied to each element
	/// in order.
	///
	/// # Examples
	///
	/// ```
	/// let x = [1, 2, 3];
	/// let y = x.map(\|v\| v + 1);
	/// assert_eq!(y, [2, 3, 4]);
	///
	/// let x = [1, 2, 3];
	/// let mut temp = 0;
	/// let y = x.map(\|v\| { temp += 1; v * temp });
	/// assert_eq!(y, [1, 4, 9]);
	///
	/// let x = ["Ferris", "Bueller's", "Day", "Off"];
	/// let y = x.map(\|v\| v.len());
	/// assert_eq!(y, [6, 9, 3, 3]);
	/// ```
	#[stable(feature = "array_map", since = "1.55.0")]
	pub fn map<F, U>(self, f: F) -> [U; N]
	where
	F: FnMut(T) -> U,
	{
	// SAFETY: we know for certain that this iterator will yield exactly `N`
	// items.
	unsafe { collect_into_array_unchecked(&mut IntoIterator::into_iter(self).map(f)) }
	}

	/// 'Zips up' two arrays into a single array of pairs.
	///
	/// `zip()` returns a new array where every element is a tuple where the
	/// first element comes from the first array, and the second element comes
	/// from the second array. In other words, it zips two arrays together,
	/// into a single one.
	///
	/// # Examples
	///
	/// ```
	/// #![feature(array_zip)]
	/// let x = [1, 2, 3];
	/// let y = [4, 5, 6];
	/// let z = x.zip(y);
	/// assert_eq!(z, [(1, 4), (2, 5), (3, 6)]);
	/// ```
	#[unstable(feature = "array_zip", issue = "80094")]
	pub fn zip<U>(self, rhs: [U; N]) -> [(T, U); N] {
	let mut iter = IntoIterator::into_iter(self).zip(rhs);

	// SAFETY: we know for certain that this iterator will yield exactly `N`
	// items.
	unsafe { collect_into_array_unchecked(&mut iter) }
	}

	/// Returns a slice containing the entire array. Equivalent to `&s[..]`.
	#[unstable(feature = "array_methods", issue = "76118")]
	pub fn as_slice(&self) -> &[T] {
	self
	}

	/// Returns a mutable slice containing the entire array. Equivalent to
	/// `&mut s[..]`.
	#[unstable(feature = "array_methods", issue = "76118")]
	pub fn as_mut_slice(&mut self) -> &mut [T] {
	self
	}

	/// Borrows each element and returns an array of references with the same
	/// size as `self`.
	///
	///
	/// # Example
	///
	/// ```
	/// #![feature(array_methods)]
	///
	/// let floats = [3.1, 2.7, -1.0];
	/// let float_refs: [&f64; 3] = floats.each_ref();
	/// assert_eq!(float_refs, [&3.1, &2.7, &-1.0]);
	/// ```
	///
	/// This method is particularly useful if combined with other methods, like
	/// [`map`](#method.map). This way, you can avoid moving the original
	/// array if its elements are not `Copy`.
	///
	/// ```
	/// #![feature(array_methods)]
	///
	/// let strings = ["Ferris".to_string(), "♥".to_string(), "Rust".to_string()];
	/// let is_ascii = strings.each_ref().map(\|s\| s.is_ascii());
	/// assert_eq!(is_ascii, [true, false, true]);
	///
	/// // We can still access the original array: it has not been moved.
	/// assert_eq!(strings.len(), 3);
	/// ```
	#[unstable(feature = "array_methods", issue = "76118")]
	pub fn each_ref(&self) -> [&T; N] {
	// SAFETY: we know for certain that this iterator will yield exactly `N`
	// items.
	unsafe { collect_into_array_unchecked(&mut self.iter()) }
	}

	/// Borrows each element mutably and returns an array of mutable references
	/// with the same size as `self`.
	///
	///
	/// # Example
	///
	/// ```
	/// #![feature(array_methods)]
	///
	/// let mut floats = [3.1, 2.7, -1.0];
	/// let float_refs: [&mut f64; 3] = floats.each_mut();
	/// *float_refs[0] = 0.0;
	/// assert_eq!(float_refs, [&mut 0.0, &mut 2.7, &mut -1.0]);
	/// assert_eq!(floats, [0.0, 2.7, -1.0]);
	/// ```
	#[unstable(feature = "array_methods", issue = "76118")]
	pub fn each_mut(&mut self) -> [&mut T; N] {
	// SAFETY: we know for certain that this iterator will yield exactly `N`
	// items.
	unsafe { collect_into_array_unchecked(&mut self.iter_mut()) }
	}
	}

	/// Pulls `N` items from `iter` and returns them as an array. If the iterator
	/// yields fewer than `N` items, this function exhibits undefined behavior.
	///
	/// See [`collect_into_array`] for more information.
	///
	///
	/// # Safety
	///
	/// It is up to the caller to guarantee that `iter` yields at least `N` items.
	/// Violating this condition causes undefined behavior.
	unsafe fn collect_into_array_unchecked<I, const N: usize>(iter: &mut I) -> [I::Item; N]
	where
	// Note: `TrustedLen` here is somewhat of an experiment. This is just an
	// internal function, so feel free to remove if this bound turns out to be a
	// bad idea. In that case, remember to also remove the lower bound
	// `debug_assert!` below!
	I: Iterator + TrustedLen,
	{
	debug_assert!(N <= iter.size_hint().1.unwrap_or(usize::MAX));
	debug_assert!(N <= iter.size_hint().0);

	match collect_into_array(iter) {
	Some(array) => array,
	// SAFETY: covered by the function contract.
	None => unsafe { crate::hint::unreachable_unchecked() },
	}
	}

	/// Pulls `N` items from `iter` and returns them as an array. If the iterator
	/// yields fewer than `N` items, `None` is returned and all already yielded
	/// items are dropped.
	///
	/// Since the iterator is passed as a mutable reference and this function calls
	/// `next` at most `N` times, the iterator can still be used afterwards to
	/// retrieve the remaining items.
	///
	/// If `iter.next()` panicks, all items already yielded by the iterator are
	/// dropped.
	fn collect_into_array<I, const N: usize>(iter: &mut I) -> Option<[I::Item; N]>
	where
	I: Iterator,
	{
	if N == 0 {
	// SAFETY: An empty array is always inhabited and has no validity invariants.
	return unsafe { Some(mem::zeroed()) };
	}

	struct Guard<T, const N: usize> {
	ptr: *mut T,
	initialized: usize,
	}

	impl<T, const N: usize> Drop for Guard<T, N> {
	fn drop(&mut self) {
	debug_assert!(self.initialized <= N);

	let initialized_part = crate::ptr::slice_from_raw_parts_mut(self.ptr, self.initialized);

	// SAFETY: this raw slice will contain only initialized objects.
	unsafe {
	crate::ptr::drop_in_place(initialized_part);
	}
	}
	}

	let mut array = MaybeUninit::uninit_array::<N>();
	let mut guard: Guard<_, N> =
	Guard { ptr: MaybeUninit::slice_as_mut_ptr(&mut array), initialized: 0 };

	while let Some(item) = iter.next() {
	// SAFETY: `guard.initialized` starts at 0, is increased by one in the
	// loop and the loop is aborted once it reaches N (which is
	// `array.len()`).
	unsafe {
	array.get_unchecked_mut(guard.initialized).write(item);
	}
	guard.initialized += 1;

	// Check if the whole array was initialized.
	if guard.initialized == N {
	mem::forget(guard);

	// SAFETY: the condition above asserts that all elements are
	// initialized.
	let out = unsafe { MaybeUninit::array_assume_init(array) };
	return Some(out);
	}
	}

	// This is only reached if the iterator is exhausted before
	// `guard.initialized` reaches `N`. Also note that `guard` is dropped here,
	// dropping all already initialized elements.
	None
	}