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Add RefCell<T>::replace_with

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This commit is contained in:
Havvy 2017-11-06 18:53:23 -08:00
parent bd0e45a323
commit 2d02772993
1 changed files with 39 additions and 14 deletions
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53
src/libcore/cell.rs
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@ -579,32 +579,62 @@ impl<T> RefCell<T> {
///
/// This function corresponds to [`std::mem::replace`](../mem/fn.replace.html).
///
/// # Panics
///
/// Panics if the value is currently borrowed.
///
/// # Examples
///
/// ```
/// #![feature(refcell_replace_swap)]
/// use std::cell::RefCell;
/// let c = RefCell::new(5);
/// let u = c.replace(6);
/// assert_eq!(u, 5);
/// assert_eq!(c, RefCell::new(6));
/// let cell = RefCell::new(5);
/// let old_value = cell.replace(6);
/// assert_eq!(old_value, 5);
/// assert_eq!(cell, RefCell::new(6));
/// ```
///
/// # Panics
///
/// This function will panic if the `RefCell` has any outstanding borrows,
/// whether or not they are full mutable borrows.
#[inline]
#[unstable(feature = "refcell_replace_swap", issue="43570")]
pub fn replace(&self, t: T) -> T {
mem::replace(&mut *self.borrow_mut(), t)
}
/// Replaces the wrapped value with a new one computed from `f`, returning
/// the old value, without deinitializing either one.
///
/// This function corresponds to [`std::mem::replace`](../mem/fn.replace.html).
///
/// # Panics
///
/// Panics if the value is currently borrowed.
///
/// # Examples
///
/// ```
/// #![feature(refcell_replace_swap)]
/// use std::cell::RefCell;
/// let cell = RefCell::new(5);
/// let old_value = cell.replace_with(|&mut old| old + 1);
/// assert_eq!(old_value, 5);
/// assert_eq!(cell, RefCell::new(6));
/// ```
#[inline]
#[unstable(feature = "refcell_replace_swap", issue="43570")]
pub fn replace_with<F: FnOnce(&mut T) -> T>(&self, f: F) -> T {
let mut_borrow = &mut *self.borrow_mut();
let replacement = f(mut_borrow);
mem::replace(mut_borrow, replacement)
}
/// Swaps the wrapped value of `self` with the wrapped value of `other`,
/// without deinitializing either one.
///
/// This function corresponds to [`std::mem::swap`](../mem/fn.swap.html).
///
/// # Panics
///
/// Panics if the value in either `RefCell` is currently borrowed.
///
/// # Examples
///
/// ```
@ -616,11 +646,6 @@ impl<T> RefCell<T> {
/// assert_eq!(c, RefCell::new(6));
/// assert_eq!(d, RefCell::new(5));
/// ```
///
/// # Panics
///
/// This function will panic if either `RefCell` has any outstanding borrows,
/// whether or not they are full mutable borrows.
#[inline]
#[unstable(feature = "refcell_replace_swap", issue="43570")]
pub fn swap(&self, other: &Self) {