1 //! Implementations of things like `Eq` for fixed-length arrays
2 //! up to a certain length. Eventually we should be able to generalize
5 //! *[See also the array primitive type](../../std/primitive.array.html).*
7 #![stable(feature = "core_array", since = "1.36.0")]
9 use crate::borrow::{Borrow, BorrowMut};
10 use crate::cmp::Ordering;
11 use crate::convert::{Infallible, TryFrom};
13 use crate::hash::{Hash, self};
14 use crate::marker::Unsize;
15 use crate::slice::{Iter, IterMut};
19 #[unstable(feature = "array_value_iter", issue = "65798")]
20 pub use iter::IntoIter;
22 /// Utility trait implemented only on arrays of fixed size
24 /// This trait can be used to implement other traits on fixed-size arrays
25 /// without causing much metadata bloat.
27 /// The trait is marked unsafe in order to restrict implementors to fixed-size
28 /// arrays. User of this trait can assume that implementors have the exact
29 /// layout in memory of a fixed size array (for example, for unsafe
32 /// Note that the traits [`AsRef`] and [`AsMut`] provide similar methods for types that
33 /// may not be fixed-size arrays. Implementors should prefer those traits
36 /// [`AsRef`]: ../convert/trait.AsRef.html
37 /// [`AsMut`]: ../convert/trait.AsMut.html
38 #[unstable(feature = "fixed_size_array", issue = "27778")]
39 pub unsafe trait FixedSizeArray<T> {
40 /// Converts the array to immutable slice
41 #[unstable(feature = "fixed_size_array", issue = "27778")]
42 fn as_slice(&self) -> &[T];
43 /// Converts the array to mutable slice
44 #[unstable(feature = "fixed_size_array", issue = "27778")]
45 fn as_mut_slice(&mut self) -> &mut [T];
48 #[unstable(feature = "fixed_size_array", issue = "27778")]
49 unsafe impl<T, A: Unsize<[T]>> FixedSizeArray<T> for A {
51 fn as_slice(&self) -> &[T] {
55 fn as_mut_slice(&mut self) -> &mut [T] {
60 /// The error type returned when a conversion from a slice to an array fails.
61 #[stable(feature = "try_from", since = "1.34.0")]
62 #[derive(Debug, Copy, Clone)]
63 pub struct TryFromSliceError(());
65 #[stable(feature = "core_array", since = "1.36.0")]
66 impl fmt::Display for TryFromSliceError {
68 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
69 fmt::Display::fmt(self.__description(), f)
73 impl TryFromSliceError {
74 #[unstable(feature = "array_error_internals",
75 reason = "available through Error trait and this method should not \
80 pub fn __description(&self) -> &str {
81 "could not convert slice to array"
85 #[stable(feature = "try_from_slice_error", since = "1.36.0")]
86 impl From<Infallible> for TryFromSliceError {
87 fn from(x: Infallible) -> TryFromSliceError {
92 #[stable(feature = "rust1", since = "1.0.0")]
93 impl<T, const N: usize> AsRef<[T]> for [T; N]
95 [T; N]: LengthAtMost32,
98 fn as_ref(&self) -> &[T] {
103 #[stable(feature = "rust1", since = "1.0.0")]
104 impl<T, const N: usize> AsMut<[T]> for [T; N]
106 [T; N]: LengthAtMost32,
109 fn as_mut(&mut self) -> &mut [T] {
114 #[stable(feature = "array_borrow", since = "1.4.0")]
115 impl<T, const N: usize> Borrow<[T]> for [T; N]
117 [T; N]: LengthAtMost32,
119 fn borrow(&self) -> &[T] {
124 #[stable(feature = "array_borrow", since = "1.4.0")]
125 impl<T, const N: usize> BorrowMut<[T]> for [T; N]
127 [T; N]: LengthAtMost32,
129 fn borrow_mut(&mut self) -> &mut [T] {
134 #[stable(feature = "try_from", since = "1.34.0")]
135 impl<T, const N: usize> TryFrom<&[T]> for [T; N]
138 [T; N]: LengthAtMost32,
140 type Error = TryFromSliceError;
142 fn try_from(slice: &[T]) -> Result<[T; N], TryFromSliceError> {
143 <&Self>::try_from(slice).map(|r| *r)
147 #[stable(feature = "try_from", since = "1.34.0")]
148 impl<'a, T, const N: usize> TryFrom<&'a [T]> for &'a [T; N]
150 [T; N]: LengthAtMost32,
152 type Error = TryFromSliceError;
154 fn try_from(slice: &[T]) -> Result<&[T; N], TryFromSliceError> {
155 if slice.len() == N {
156 let ptr = slice.as_ptr() as *const [T; N];
157 // SAFETY: ok because we just checked that the length fits
160 Err(TryFromSliceError(()))
165 #[stable(feature = "try_from", since = "1.34.0")]
166 impl<'a, T, const N: usize> TryFrom<&'a mut [T]> for &'a mut [T; N]
168 [T; N]: LengthAtMost32,
170 type Error = TryFromSliceError;
172 fn try_from(slice: &mut [T]) -> Result<&mut [T; N], TryFromSliceError> {
173 if slice.len() == N {
174 let ptr = slice.as_mut_ptr() as *mut [T; N];
175 // SAFETY: ok because we just checked that the length fits
176 unsafe { Ok(&mut *ptr) }
178 Err(TryFromSliceError(()))
183 #[stable(feature = "rust1", since = "1.0.0")]
184 impl<T: Hash, const N: usize> Hash for [T; N]
186 [T; N]: LengthAtMost32,
188 fn hash<H: hash::Hasher>(&self, state: &mut H) {
189 Hash::hash(&self[..], state)
193 #[stable(feature = "rust1", since = "1.0.0")]
194 impl<T: fmt::Debug, const N: usize> fmt::Debug for [T; N]
196 [T; N]: LengthAtMost32,
198 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
199 fmt::Debug::fmt(&&self[..], f)
203 #[stable(feature = "rust1", since = "1.0.0")]
204 impl<'a, T, const N: usize> IntoIterator for &'a [T; N]
206 [T; N]: LengthAtMost32,
209 type IntoIter = Iter<'a, T>;
211 fn into_iter(self) -> Iter<'a, T> {
216 #[stable(feature = "rust1", since = "1.0.0")]
217 impl<'a, T, const N: usize> IntoIterator for &'a mut [T; N]
219 [T; N]: LengthAtMost32,
221 type Item = &'a mut T;
222 type IntoIter = IterMut<'a, T>;
224 fn into_iter(self) -> IterMut<'a, T> {
229 #[stable(feature = "rust1", since = "1.0.0")]
230 impl<A, B, const N: usize> PartialEq<[B; N]> for [A; N]
233 [A; N]: LengthAtMost32,
234 [B; N]: LengthAtMost32,
237 fn eq(&self, other: &[B; N]) -> bool {
238 self[..] == other[..]
241 fn ne(&self, other: &[B; N]) -> bool {
242 self[..] != other[..]
246 #[stable(feature = "rust1", since = "1.0.0")]
247 impl<A, B, const N: usize> PartialEq<[B]> for [A; N]
250 [A; N]: LengthAtMost32,
253 fn eq(&self, other: &[B]) -> bool {
254 self[..] == other[..]
257 fn ne(&self, other: &[B]) -> bool {
258 self[..] != other[..]
262 #[stable(feature = "rust1", since = "1.0.0")]
263 impl<A, B, const N: usize> PartialEq<[A; N]> for [B]
266 [A; N]: LengthAtMost32,
269 fn eq(&self, other: &[A; N]) -> bool {
270 self[..] == other[..]
273 fn ne(&self, other: &[A; N]) -> bool {
274 self[..] != other[..]
278 #[stable(feature = "rust1", since = "1.0.0")]
279 impl<'b, A, B, const N: usize> PartialEq<&'b [B]> for [A; N]
282 [A; N]: LengthAtMost32,
285 fn eq(&self, other: &&'b [B]) -> bool {
286 self[..] == other[..]
289 fn ne(&self, other: &&'b [B]) -> bool {
290 self[..] != other[..]
294 #[stable(feature = "rust1", since = "1.0.0")]
295 impl<'b, A, B, const N: usize> PartialEq<[A; N]> for &'b [B]
298 [A; N]: LengthAtMost32,
301 fn eq(&self, other: &[A; N]) -> bool {
302 self[..] == other[..]
305 fn ne(&self, other: &[A; N]) -> bool {
306 self[..] != other[..]
310 #[stable(feature = "rust1", since = "1.0.0")]
311 impl<'b, A, B, const N: usize> PartialEq<&'b mut [B]> for [A; N]
314 [A; N]: LengthAtMost32,
317 fn eq(&self, other: &&'b mut [B]) -> bool {
318 self[..] == other[..]
321 fn ne(&self, other: &&'b mut [B]) -> bool {
322 self[..] != other[..]
326 #[stable(feature = "rust1", since = "1.0.0")]
327 impl<'b, A, B, const N: usize> PartialEq<[A; N]> for &'b mut [B]
330 [A; N]: LengthAtMost32,
333 fn eq(&self, other: &[A; N]) -> bool {
334 self[..] == other[..]
337 fn ne(&self, other: &[A; N]) -> bool {
338 self[..] != other[..]
342 // NOTE: some less important impls are omitted to reduce code bloat
343 // __impl_slice_eq2! { [A; $N], &'b [B; $N] }
344 // __impl_slice_eq2! { [A; $N], &'b mut [B; $N] }
346 #[stable(feature = "rust1", since = "1.0.0")]
347 impl<T: Eq, const N: usize> Eq for [T; N] where [T; N]: LengthAtMost32 {}
349 #[stable(feature = "rust1", since = "1.0.0")]
350 impl<T: PartialOrd, const N: usize> PartialOrd for [T; N]
352 [T; N]: LengthAtMost32,
355 fn partial_cmp(&self, other: &[T; N]) -> Option<Ordering> {
356 PartialOrd::partial_cmp(&&self[..], &&other[..])
359 fn lt(&self, other: &[T; N]) -> bool {
360 PartialOrd::lt(&&self[..], &&other[..])
363 fn le(&self, other: &[T; N]) -> bool {
364 PartialOrd::le(&&self[..], &&other[..])
367 fn ge(&self, other: &[T; N]) -> bool {
368 PartialOrd::ge(&&self[..], &&other[..])
371 fn gt(&self, other: &[T; N]) -> bool {
372 PartialOrd::gt(&&self[..], &&other[..])
376 #[stable(feature = "rust1", since = "1.0.0")]
377 impl<T: Ord, const N: usize> Ord for [T; N]
379 [T; N]: LengthAtMost32,
382 fn cmp(&self, other: &[T; N]) -> Ordering {
383 Ord::cmp(&&self[..], &&other[..])
387 /// Implemented for lengths where trait impls are allowed on arrays in core/std
388 #[rustc_on_unimplemented(
389 message="arrays only have std trait implementations for lengths 0..=32",
391 #[unstable(feature = "const_generic_impls_guard", issue = "0",
392 reason = "will never be stable, just a temporary step until const generics are stable")]
393 pub trait LengthAtMost32 {}
395 macro_rules! array_impls {
396 ($($N:literal)+) => {
398 #[unstable(feature = "const_generic_impls_guard", issue = "0")]
399 impl<T> LengthAtMost32 for [T; $N] {}
406 10 11 12 13 14 15 16 17 18 19
407 20 21 22 23 24 25 26 27 28 29
411 // The Default impls cannot be generated using the array_impls! macro because
412 // they require array literals.
414 macro_rules! array_impl_default {
415 {$n:expr, $t:ident $($ts:ident)*} => {
416 #[stable(since = "1.4.0", feature = "array_default")]
417 impl<T> Default for [T; $n] where T: Default {
418 fn default() -> [T; $n] {
419 [$t::default(), $($ts::default()),*]
422 array_impl_default!{($n - 1), $($ts)*}
425 #[stable(since = "1.4.0", feature = "array_default")]
426 impl<T> Default for [T; $n] {
427 fn default() -> [T; $n] { [] }
432 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}