Struct PeekMut

1.12.0 · Source
pub struct PeekMut<'a, T, A = Global>
where T: 'a + Ord, A: Allocator,
{ heap: &'a mut BinaryHeap<T, A>, original_len: Option<NonZero<usize>>, }
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.

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§heap: &'a mut BinaryHeap<T, A>§original_len: Option<NonZero<usize>>

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

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pub fn refresh(&mut self) -> bool

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

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

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

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

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

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

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

Mutably dereferences the value.
1.12.0 · Source§

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

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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>

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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>

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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> ArchivePointee for T

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type ArchivedMetadata = ()

The archived version of the pointer metadata for this type.
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fn pointer_metadata( _: &<T as ArchivePointee>::ArchivedMetadata, ) -> <T as Pointee>::Metadata

Converts some archived metadata to the pointer metadata for itself.
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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<T> LayoutRaw for T

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fn layout_raw(_: <T as Pointee>::Metadata) -> Result<Layout, LayoutError>

Returns the layout of the type.
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impl<T, N1, N2> Niching<NichedOption<T, N1>> for N2
where T: SharedNiching<N1, N2>, N1: Niching<T>, N2: Niching<T>,

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unsafe fn is_niched(niched: *const NichedOption<T, N1>) -> bool

Returns whether the given value has been niched. Read more
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fn resolve_niched(out: Place<NichedOption<T, N1>>)

Writes data to out indicating that a T is niched.
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impl<T> Pointee for T

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type Metadata = ()

The metadata type for pointers and references to this type.
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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)
The target type on which the method may be called.
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impl<T> Same for T

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type Output = T

Should always be Self
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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.
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impl<T> Upcastable for T
where T: Any + Send + Sync + 'static,

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fn upcast_any_ref(&self) -> &(dyn Any + 'static)

upcast ref
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fn upcast_any_mut(&mut self) -> &mut (dyn Any + 'static)

upcast mut ref
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fn upcast_any_box(self: Box<T>) -> Box<dyn Any>

upcast boxed dyn