# Struct PeekMut

1.36.0 · Source

    pub struct PeekMut<'a, T: 'a + Ord, A: Allocator = Global> { /* private fields */ }

Expand description

Structure wrapping a mutable reference to the greatest item on a `BinaryHeap`.

This `struct` is created by the `peek_mut` method on `BinaryHeap`. See its documentation for more.

## Implementations§

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### impl<'a, T: Ord, A: Allocator> PeekMut<'a, T, A>

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#### pub fn refresh(&mut self) -> bool

🔬This is a nightly-only experimental API. (`binary_heap_peek_mut_refresh` #138355)

Sifts the current element to its new position.

Afterwards refers to the new element. Returns if the element changed.

###### §Examples

The condition can be used to upper bound all elements in the heap. When only few elements are affected, the heap’s sort ensures this is faster than a reconstruction from the raw element list and requires no additional allocation.

    #![feature(binary_heap_peek_mut_refresh)]
    use std::collections::BinaryHeap;

    let mut heap: BinaryHeap<u32> = (0..128).collect();
    let mut peek = heap.peek_mut().unwrap();

    loop {
        *peek = 99;

        if !peek.refresh() {
            break;
        }
    }

    // Post condition, this is now an upper bound.
    assert!(*peek < 100);

When the element remains the maximum after modification, the peek remains unchanged:

    #![feature(binary_heap_peek_mut_refresh)]
    use std::collections::BinaryHeap;

    let mut heap: BinaryHeap<u32> = [1, 2, 3].into();
    let mut peek = heap.peek_mut().unwrap();

    assert_eq!(*peek, 3);
    *peek = 42;

    // When we refresh, the peek is updated to the new maximum.
    assert!(!peek.refresh(), "42 is even larger than 3");
    assert_eq!(*peek, 42);

1.18.0 · Source

#### pub fn pop(this: PeekMut<'a, T, A>) -> T

Removes the peeked value from the heap and returns it.

## Trait Implementations§

1.17.0 · Source§

### impl<T: Ord + Debug, A: Allocator> Debug for PeekMut<'_, T, A>

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#### fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter. Read more
1.12.0 · Source§

### impl<T: Ord, A: Allocator> Deref for PeekMut<'_, T, A>

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#### type Target = T

The resulting type after dereferencing.
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#### fn deref(&self) -> &T

Dereferences the value.
1.12.0 · Source§

### impl<T: Ord, A: Allocator> DerefMut for PeekMut<'_, T, A>

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#### fn deref_mut(&mut self) -> &mut T

Mutably dereferences the value.
1.12.0 · Source§

### impl<T: Ord, A: Allocator> Drop for PeekMut<'_, T, A>

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#### fn drop(&mut self)

Executes the destructor for this type. Read more

## Auto Trait Implementations§

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### impl<'a, T, A> Freeze for PeekMut<'a, T, A>

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### impl<'a, T, A> RefUnwindSafe for PeekMut<'a, T, A>
where A: RefUnwindSafe, T: RefUnwindSafe,

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### impl<'a, T, A> Send for PeekMut<'a, T, A>
where A: Send, T: Send,

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### impl<'a, T, A> Sync for PeekMut<'a, T, A>
where A: Sync, T: Sync,

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### impl<'a, T, A> Unpin for PeekMut<'a, T, A>

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### impl<'a, T, A = Global> !UnwindSafe for PeekMut<'a, T, A>

## Blanket Implementations§

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### impl<T> Any for T
where T: 'static + ?Sized,

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#### fn type_id(&self) -> TypeId

Gets the `TypeId` of `self`. Read more
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### impl<T> Borrow<T> for T
where T: ?Sized,

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#### fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more
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### impl<T> BorrowMut<T> for T
where T: ?Sized,

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#### fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value. Read more
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### impl<T> From<T> for T

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#### fn from(t: T) -> T

Returns the argument unchanged.

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### impl<T, U> Into<U> for T
where U: From<T>,

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#### fn into(self) -> U

Calls `U::from(self)`.

That is, this conversion is whatever the implementation of `From<T> for U` chooses to do.

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### impl<P, T> Receiver for P
where P: Deref<Target = T> + ?Sized, T: ?Sized,

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#### type Target = T

🔬This is a nightly-only experimental API. (`arbitrary_self_types` #44874)
The target type on which the method may be called.
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### impl<T, U> TryFrom<U> for T
where U: Into<T>,

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#### type Error = Infallible

The type returned in the event of a conversion error.
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#### fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

Performs the conversion.
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### impl<T, U> TryInto<U> for T
where U: TryFrom<T>,

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#### type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.
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#### fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.