Implement `shrink_to` method on collections

1 files changed, 25 insertions, 0 deletions

diff --git a/src/liballoc/binary_heap.rs b/src/liballoc/binary_heap.rs
index 8aaac5d6e08..f6a666b599b 100644
--- a/src/liballoc/binary_heap.rs
+++ b/src/liballoc/binary_heap.rs
@@ -509,6 +509,31 @@ impl<T: Ord> BinaryHeap<T> {
         self.data.shrink_to_fit();
     }
 
+    /// Discards capacity with a lower bound.
+    ///
+    /// The capacity will remain at least as large as both the length
+    /// and the supplied value.
+    ///
+    /// Panics if the current capacity is smaller than the supplied
+    /// minimum capacity.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(shrink_to)]
+    /// use std::collections::BinaryHeap;
+    /// let mut heap: BinaryHeap<i32> = BinaryHeap::with_capacity(100);
+    ///
+    /// assert!(heap.capacity() >= 100);
+    /// heap.shrink_to(10);
+    /// assert!(heap.capacity() >= 10);
+    /// ```
+    #[inline]
+    #[unstable(feature = "shrink_to", reason = "new API", issue="0")]
+    pub fn shrink_to(&mut self, min_capacity: usize) {
+        self.data.shrink_to(min_capacity)
+    }
+
     /// Removes the greatest item from the binary heap and returns it, or `None` if it
     /// is empty.
     ///