//! Implementations of things like `Eq` for fixed-length arrays//! up to a certain length. Eventually, we should be able to generalize//! to all lengths.//!//! *[See also the array primitive type](../../std/primitive.array.html).* #![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::marker::Unsize;use crate::slice::{Iter, IterMut}; mod iter; #[unstable(feature = "array_value_iter", issue = "65798")]pub use iter::IntoIter; /// Converts a reference to `T` into a reference to an array of length 1 (without copying).#[unstable(feature = "array_from_ref", issue = "77101")]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).#[unstable(feature = "array_from_ref", issue = "77101")]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]>() }} /// Utility trait implemented only on arrays of fixed size////// This trait can be used to implement other traits on fixed-size arrays/// without causing much metadata bloat.////// The trait is marked unsafe in order to restrict implementors to fixed-size/// arrays. User of this trait can assume that implementors have the exact/// layout in memory of a fixed size array (for example, for unsafe/// initialization).////// Note that the traits [`AsRef`] and [`AsMut`] provide similar methods for types that/// may not be fixed-size arrays. Implementors should prefer those traits/// instead.#[unstable(feature = "fixed_size_array", issue = "27778")]pub unsafe trait FixedSizeArray<T> {    /// Converts the array to immutable slice    #[unstable(feature = "fixed_size_array", issue = "27778")]    fn as_slice(&self) -> &[T];    /// Converts the array to mutable slice    #[unstable(feature = "fixed_size_array", issue = "27778")]    fn as_mut_slice(&mut self) -> &mut [T];} #[unstable(feature = "fixed_size_array", issue = "27778")]unsafe impl<T, A: Unsize<[T]>> FixedSizeArray<T> for A {    #[inline]    fn as_slice(&self) -> &[T] {        self    }    #[inline]    fn as_mut_slice(&mut self) -> &mut [T] {        self    }} /// 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(()))        }    }} #[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)    }} #[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 = "rust1", since = "1.0.0")]impl<A, B, const N: usize> PartialEq<[B; N]> for [A; N]where    A: PartialEq<B>,{    #[inline]    fn eq(&self, other: &[B; N]) -> bool {        self[..] == other[..]    }    #[inline]    fn ne(&self, other: &[B; N]) -> bool {        self[..] != other[..]    }} #[stable(feature = "rust1", since = "1.0.0")]impl<A, B, const N: usize> PartialEq<[B]> for [A; N]where    A: PartialEq<B>,{    #[inline]    fn eq(&self, other: &[B]) -> bool {        self[..] == other[..]    }    #[inline]    fn ne(&self, other: &[B]) -> bool {        self[..] != other[..]    }} #[stable(feature = "rust1", since = "1.0.0")]impl<A, B, const N: usize> PartialEq<[A; N]> for [B]where    B: PartialEq<A>,{    #[inline]    fn eq(&self, other: &[A; N]) -> bool {        self[..] == other[..]    }    #[inline]    fn ne(&self, other: &[A; N]) -> bool {        self[..] != other[..]    }} #[stable(feature = "rust1", since = "1.0.0")]impl<'b, A, B, const N: usize> PartialEq<&'b [B]> for [A; N]where    A: PartialEq<B>,{    #[inline]    fn eq(&self, other: &&'b [B]) -> bool {        self[..] == other[..]    }    #[inline]    fn ne(&self, other: &&'b [B]) -> bool {        self[..] != other[..]    }} #[stable(feature = "rust1", since = "1.0.0")]impl<'b, A, B, const N: usize> PartialEq<[A; N]> for &'b [B]where    B: PartialEq<A>,{    #[inline]    fn eq(&self, other: &[A; N]) -> bool {        self[..] == other[..]    }    #[inline]    fn ne(&self, other: &[A; N]) -> bool {        self[..] != other[..]    }} #[stable(feature = "rust1", since = "1.0.0")]impl<'b, A, B, const N: usize> PartialEq<&'b mut [B]> for [A; N]where    A: PartialEq<B>,{    #[inline]    fn eq(&self, other: &&'b mut [B]) -> bool {        self[..] == other[..]    }    #[inline]    fn ne(&self, other: &&'b mut [B]) -> bool {        self[..] != other[..]    }} #[stable(feature = "rust1", since = "1.0.0")]impl<'b, A, B, const N: usize> PartialEq<[A; N]> for &'b mut [B]where    B: PartialEq<A>,{    #[inline]    fn eq(&self, other: &[A; N]) -> bool {        self[..] == other[..]    }    #[inline]    fn ne(&self, other: &[A; N]) -> bool {        self[..] != other[..]    }} // NOTE: some less important impls are omitted to reduce code bloat// __impl_slice_eq2! { [A; $N], &'b [B; $N] }// __impl_slice_eq2! { [A; $N], &'b mut [B; $N] } #[stable(feature = "rust1", since = "1.0.0")]impl<T: Eq, const N: usize> Eq for [T; N] {} #[stable(feature = "rust1", since = "1.0.0")]impl<T: PartialOrd, const N: usize> PartialOrd for [T; N] {    #[inline]    fn partial_cmp(&self, other: &[T; N]) -> Option<Ordering> {        PartialOrd::partial_cmp(&&self[..], &&other[..])    }    #[inline]    fn lt(&self, other: &[T; N]) -> bool {        PartialOrd::lt(&&self[..], &&other[..])    }    #[inline]    fn le(&self, other: &[T; N]) -> bool {        PartialOrd::le(&&self[..], &&other[..])    }    #[inline]    fn ge(&self, other: &[T; N]) -> bool {        PartialOrd::ge(&&self[..], &&other[..])    }    #[inline]    fn gt(&self, other: &[T; N]) -> bool {        PartialOrd::gt(&&self[..], &&other[..])    }} /// Implements comparison of arrays [lexicographically](Ord#lexicographical-comparison).#[stable(feature = "rust1", since = "1.0.0")]impl<T: Ord, const N: usize> Ord for [T; N] {    #[inline]    fn cmp(&self, other: &[T; N]) -> Ordering {        Ord::cmp(&&self[..], &&other[..])    }} // The Default impls cannot be done with const generics because `[T; 0]` doesn't// require Default to be implemented, and having different impl blocks for// different numbers isn't supported yet. macro_rules! array_impl_default {    {$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    ///    /// ```    /// #![feature(array_map)]    /// 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]);    /// ```    #[unstable(feature = "array_map", issue = "75243")]    pub fn map<F, U>(self, mut f: F) -> [U; N]    where        F: FnMut(T) -> U,    {        use crate::mem::MaybeUninit;        struct Guard<T, const N: usize> {            dst: *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.dst, self.initialized);                // SAFETY: this raw slice will contain only initialized objects                // that's why, it is allowed to drop it.                unsafe {                    crate::ptr::drop_in_place(initialized_part);                }            }        }        let mut dst = MaybeUninit::uninit_array::<N>();        let mut guard: Guard<U, N> =            Guard { dst: MaybeUninit::slice_as_mut_ptr(&mut dst), initialized: 0 };        for (src, dst) in IntoIter::new(self).zip(&mut dst) {            dst.write(f(src));            guard.initialized += 1;        }        // FIXME: Convert to crate::mem::transmute once it works with generics.        // unsafe { crate::mem::transmute::<[MaybeUninit<U>; N], [U; N]>(dst) }        crate::mem::forget(guard);        // SAFETY: At this point we've properly initialized the whole array        // and we just need to cast it to the correct type.        unsafe { crate::mem::transmute_copy::<_, [U; N]>(&dst) }    }     /// 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    }}