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alloc: Added as_slice method to BinaryHeap collection #82331

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Merged
merged 3 commits into from
Mar 30, 2021
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alloc: Added as_slice method to BinaryHeap collection #82331

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6233f3f
alloc: Added `as_slice` method to `BinaryHeap` collection
frol Feb 20, 2021
dd2b8a0
provide a more realistic example for BinaryHeap::as_slice
frol Mar 13, 2021
595f3f2
Updated the tracking issue #
frol Mar 29, 2021
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23 changes: 23 additions & 0 deletions library/alloc/src/collections/binary_heap.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -889,6 +889,29 @@ impl<T> BinaryHeap<T> {
self.data.shrink_to(min_capacity)
}

/// Returns a slice of all values in the underlying vector, in arbitrary
/// order.
///
/// # Examples
///
/// Basic usage:
///
/// ```
/// #![feature(binary_heap_as_slice)]
/// use std::collections::BinaryHeap;
/// let heap = BinaryHeap::from(vec![1, 2, 3, 4, 5, 6, 7]);
/// let slice = heap.as_slice();
///
/// // Will print in some order
/// for x in slice {
/// println!("{}", x);
/// }
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This is going to need a more realistic example. The point of example code is chiefly to show why you would want to call the method, not how to perform a method call. If someone is reading this documentation, we can assume they know how to make method calls. The example here does nothing to illustrate why as_slice would be used, since if you needed to do this, you should be writing for x in &heap {...} instead.

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@frol frol Mar 1, 2021 •
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@dtolnay Good question. I had bumped into it when I needed to efficiently serialize BinaryHeap. Some APIs (writer::write_all in my case) may expect a slice of data, and it is going to be quite inefficient to clone the data or iterate over it item by item (when you only have a reference to the BinaryHeap and cannot use into_vec)

/// ```
#[unstable(feature = "binary_heap_as_slice", issue = "82331")]
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the number needs to be a tracking issue, not this PR

pub fn as_slice(&self) -> &[T] {
self.data.as_slice()
}

/// Consumes the `BinaryHeap` and returns the underlying vector
/// in arbitrary order.
///
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1 change: 1 addition & 0 deletions library/alloc/tests/lib.rs
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Expand Up @@ -15,6 +15,7 @@
#![feature(binary_heap_drain_sorted)]
#![feature(slice_ptr_get)]
#![feature(binary_heap_retain)]
#![feature(binary_heap_as_slice)]
#![feature(inplace_iteration)]
#![feature(iter_map_while)]
#![feature(int_bits_const)]
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