core: implement array::repeat · model-checking/verify-rust-std@387fd1f (original) (raw)
`@@ -10,6 +10,7 @@ use crate::convert::Infallible;
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`use crate::error::Error;
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`use crate::fmt;
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`use crate::hash::{self, Hash};
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use crate::intrinsics::transmute_unchecked;
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`use crate::iter::UncheckedIterator;
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`use crate::mem::{self, MaybeUninit};
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`use crate::ops::{
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`@@ -27,6 +28,41 @@ pub(crate) use drain::drain_array_with;
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`#[stable(feature = "array_value_iter", since = "1.51.0")]
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`pub use iter::IntoIter;
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/// Creates an array of type [T; N] by repeatedly cloning a value.
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///
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/// The value will be used as the last element of the resulting array, so it
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/// will be cloned N - 1 times. If N is zero, the value will be dropped.
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///
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/// # Example
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///
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/// Creating muliple copies of a string:
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/// ```rust
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/// #![feature(array_repeat)]
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///
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/// use std::array;
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///
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/// let string = "Hello there!".to_string();
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/// let strings = array::repeat(string);
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/// assert_eq!(strings, ["Hello there!", "Hello there!"]);
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/// ```
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#[inline]
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#[unstable(feature = "array_repeat", issue = "none")]
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pub fn repeat<T: Clone, const N: usize>(val: T) -> [T; N] {
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match N {
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// SAFETY: we know N to be 0 at this point.
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0 => unsafe { transmute_unchecked::<[T; 0], [T; N]>([]) },
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// SAFETY: we know N to be 1 at this point.
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1 => unsafe { transmute_unchecked::<[T; 1], [T; N]>([val]) },
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_ => {
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let mut array = MaybeUninit::uninit_array::();
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try_from_fn_erased(&mut array[..N - 1], NeverShortCircuit::wrap_mut_1(|_| val.clone()));
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array[N - 1].write(val);
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// SAFETY: all elements were initialized.
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unsafe { MaybeUninit::array_assume_init(array) }
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}
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}
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}
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`` /// Creates an array of type [T; N], where each element T is the returned value from cb
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`/// using that element's index.
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`///
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