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clarify swap

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This commit is contained in:
Ralf Jung 2018-09-18 21:14:31 +02:00
parent 0ec87d0c92
commit adcc0d2168
1 changed files with 10 additions and 5 deletions
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15
src/libcore/ptr.rs
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@ -236,7 +236,7 @@ pub const fn null_mut<T>() -> *mut T { 0 as *mut T }
///
/// * The two pointed-to values may overlap. If the values do overlap, then the
/// overlapping region of memory from `x` will be used. This is demonstrated
/// in the examples below.
/// in the second example below.
///
/// [`mem::swap`]: ../mem/fn.swap.html
///
@ -261,8 +261,8 @@ pub const fn null_mut<T>() -> *mut T { 0 as *mut T }
///
/// let mut array = [0, 1, 2, 3];
///
/// let x = array[0..].as_mut_ptr() as *mut [u32; 2];
/// let y = array[2..].as_mut_ptr() as *mut [u32; 2];
/// let x = array[0..].as_mut_ptr() as *mut [u32; 2]; // this is `array[0..2]`
/// let y = array[2..].as_mut_ptr() as *mut [u32; 2]; // this is `array[2..4]`
///
/// unsafe {
/// ptr::swap(x, y);
@ -277,11 +277,16 @@ pub const fn null_mut<T>() -> *mut T { 0 as *mut T }
///
/// let mut array = [0, 1, 2, 3];
///
/// let x = array[0..].as_mut_ptr() as *mut [u32; 3];
/// let y = array[1..].as_mut_ptr() as *mut [u32; 3];
/// let x = array[0..].as_mut_ptr() as *mut [u32; 3]; // this is `array[0..3]`
/// let y = array[1..].as_mut_ptr() as *mut [u32; 3]; // this is `array[1..4]`
///
/// unsafe {
/// ptr::swap(x, y);
/// // The indices `1..3` of the slice overlap between `x` and `y`.
/// // Reasonable results would be for to them be `[2, 3]`, so that indices `0..3` are
/// // `[1, 2, 3]` (matching `y` before the `swap`); or for them to be `[0, 1]`
/// // so that indices `1..4` are `[0, 1, 2]` (matching `x` before the `swap`).
/// // This implementation is defined to make the latter choice.
/// assert_eq!([1, 0, 1, 2], array);
/// }
/// ```