Drain { base: self.base.drain() }
}
+ /// Creates an iterator which uses a closure to determine if an element should be removed.
+ ///
+ /// If the closure returns true, the element is removed from the map and yielded.
+ /// If the closure returns false, or panics, the element remains in the map and will not be
+ /// yielded.
+ ///
+ /// Note that `drain_filter` lets you mutate every value in the filter closure, regardless of
+ /// whether you choose to keep or remove it.
+ ///
+ /// If the iterator is only partially consumed or not consumed at all, each of the remaining
+ /// elements will still be subjected to the closure and removed and dropped if it returns true.
+ ///
+ /// It is unspecified how many more elements will be subjected to the closure
+ /// if a panic occurs in the closure, or a panic occurs while dropping an element,
+ /// or if the `DrainFilter` value is leaked.
+ ///
+ /// # Examples
+ ///
+ /// Splitting a map into even and odd keys, reusing the original map:
+ ///
+ /// ```
+ /// #![feature(hash_drain_filter)]
+ /// use std::collections::HashMap;
+ ///
+ /// let mut map: HashMap<i32, i32> = (0..8).map(|x| (x, x)).collect();
+ /// let drained: HashMap<i32, i32> = map.drain_filter(|k, _v| k % 2 == 0).collect();
+ ///
+ /// let mut evens = drained.keys().copied().collect::<Vec<_>>();
+ /// let mut odds = map.keys().copied().collect::<Vec<_>>();
+ /// evens.sort();
+ /// odds.sort();
+ ///
+ /// assert_eq!(evens, vec![0, 2, 4, 6]);
+ /// assert_eq!(odds, vec![1, 3, 5, 7]);
+ /// ```
+ #[inline]
+ #[unstable(feature = "hash_drain_filter", issue = "59618")]
+ pub fn drain_filter<F>(&mut self, pred: F) -> DrainFilter<'_, K, V, F>
+ where
+ F: FnMut(&K, &mut V) -> bool,
+ {
+ DrainFilter { base: self.base.drain_filter(pred) }
+ }
+
/// Clears the map, removing all key-value pairs. Keeps the allocated memory
/// for reuse.
///
}
}
+/// A draining, filtering iterator over the entries of a `HashMap`.
+///
+/// This `struct` is created by the [`drain_filter`] method on [`HashMap`].
+///
+/// [`drain_filter`]: HashMap::drain_filter
+#[unstable(feature = "hash_drain_filter", issue = "59618")]
+pub struct DrainFilter<'a, K, V, F>
+where
+ F: FnMut(&K, &mut V) -> bool,
+{
+ base: base::DrainFilter<'a, K, V, F>,
+}
+
/// A mutable iterator over the values of a `HashMap`.
///
/// This `struct` is created by the [`values_mut`] method on [`HashMap`]. See its
}
}
+#[unstable(feature = "hash_drain_filter", issue = "59618")]
+impl<K, V, F> Iterator for DrainFilter<'_, K, V, F>
+where
+ F: FnMut(&K, &mut V) -> bool,
+{
+ type Item = (K, V);
+
+ #[inline]
+ fn next(&mut self) -> Option<(K, V)> {
+ self.base.next()
+ }
+ #[inline]
+ fn size_hint(&self) -> (usize, Option<usize>) {
+ self.base.size_hint()
+ }
+}
+
+#[unstable(feature = "hash_drain_filter", issue = "59618")]
+impl<K, V, F> FusedIterator for DrainFilter<'_, K, V, F> where F: FnMut(&K, &mut V) -> bool {}
+
+#[unstable(feature = "hash_drain_filter", issue = "59618")]
+impl<'a, K, V, F> fmt::Debug for DrainFilter<'a, K, V, F>
+where
+ F: FnMut(&K, &mut V) -> bool,
+{
+ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+ f.pad("DrainFilter { .. }")
+ }
+}
+
impl<'a, K, V> Entry<'a, K, V> {
#[stable(feature = "rust1", since = "1.0.0")]
/// Ensures a value is in the entry by inserting the default if empty, and returns
Drain { base: self.base.drain() }
}
+ /// Creates an iterator which uses a closure to determine if a value should be removed.
+ ///
+ /// If the closure returns true, then the value is removed and yielded.
+ /// If the closure returns false, the value will remain in the list and will not be yielded
+ /// by the iterator.
+ ///
+ /// If the iterator is only partially consumed or not consumed at all, each of the remaining
+ /// values will still be subjected to the closure and removed and dropped if it returns true.
+ ///
+ /// It is unspecified how many more values will be subjected to the closure
+ /// if a panic occurs in the closure, or if a panic occurs while dropping a value, or if the
+ /// `DrainFilter` itself is leaked.
+ ///
+ /// # Examples
+ ///
+ /// Splitting a set into even and odd values, reusing the original set:
+ ///
+ /// ```
+ /// #![feature(hash_drain_filter)]
+ /// use std::collections::HashSet;
+ ///
+ /// let mut set: HashSet<i32> = (0..8).collect();
+ /// let drained: HashSet<i32> = set.drain_filter(|v| v % 2 == 0).collect();
+ ///
+ /// let mut evens = drained.into_iter().collect::<Vec<_>>();
+ /// let mut odds = set.into_iter().collect::<Vec<_>>();
+ /// evens.sort();
+ /// odds.sort();
+ ///
+ /// assert_eq!(evens, vec![0, 2, 4, 6]);
+ /// assert_eq!(odds, vec![1, 3, 5, 7]);
+ /// ```
+ #[inline]
+ #[unstable(feature = "hash_drain_filter", issue = "59618")]
+ pub fn drain_filter<F>(&mut self, pred: F) -> DrainFilter<'_, T, F>
+ where
+ F: FnMut(&T) -> bool,
+ {
+ DrainFilter { base: self.base.drain_filter(pred) }
+ }
+
/// Clears the set, removing all values.
///
/// # Examples
base: base::Drain<'a, K>,
}
+/// A draining, filtering iterator over the items of a `HashSet`.
+///
+/// This `struct` is created by the [`drain_filter`] method on [`HashSet`].
+///
+/// [`drain_filter`]: HashSet::drain_filter
+#[unstable(feature = "hash_drain_filter", issue = "59618")]
+pub struct DrainFilter<'a, K, F>
+where
+ F: FnMut(&K) -> bool,
+{
+ base: base::DrainFilter<'a, K, F>,
+}
+
/// A lazy iterator producing elements in the intersection of `HashSet`s.
///
/// This `struct` is created by the [`intersection`] method on [`HashSet`].
}
}
+#[unstable(feature = "hash_drain_filter", issue = "59618")]
+impl<K, F> Iterator for DrainFilter<'_, K, F>
+where
+ F: FnMut(&K) -> bool,
+{
+ type Item = K;
+
+ #[inline]
+ fn next(&mut self) -> Option<K> {
+ self.base.next()
+ }
+ #[inline]
+ fn size_hint(&self) -> (usize, Option<usize>) {
+ self.base.size_hint()
+ }
+}
+
+#[unstable(feature = "hash_drain_filter", issue = "59618")]
+impl<K, F> FusedIterator for DrainFilter<'_, K, F> where F: FnMut(&K) -> bool {}
+
+#[unstable(feature = "hash_drain_filter", issue = "59618")]
+impl<'a, K, F> fmt::Debug for DrainFilter<'a, K, F>
+where
+ F: FnMut(&K) -> bool,
+{
+ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+ f.pad("DrainFilter { .. }")
+ }
+}
+
#[stable(feature = "rust1", since = "1.0.0")]
impl<T, S> Clone for Intersection<'_, T, S> {
#[inline]