Rollup merge of #79026 - mbrubeck:btree_retain, r=m-ou-se
Implement BTreeMap::retain and BTreeSet::retain Adds new methods `BTreeMap::retain` and `BTreeSet::retain`. These are implemented on top of `drain_filter` (#70530). The API of these methods is identical to `HashMap::retain` and `HashSet::retain`, which were implemented in #39560 and stabilized in #36648. The docs and tests are also copied from HashMap/HashSet. The new methods are unstable, behind the `btree_retain` feature gate, with tracking issue #79025. See also rust-lang/rfcs#1338.
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commit
aa685e2024
4 changed files with 70 additions and 0 deletions
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@ -863,6 +863,30 @@ impl<K: Ord, V> BTreeMap<K, V> {
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}
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}
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/// Retains only the elements specified by the predicate.
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///
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/// In other words, remove all pairs `(k, v)` such that `f(&k, &mut v)` returns `false`.
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///
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/// # Examples
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///
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/// ```
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/// #![feature(btree_retain)]
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/// use std::collections::BTreeMap;
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///
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/// let mut map: BTreeMap<i32, i32> = (0..8).map(|x| (x, x*10)).collect();
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/// // Keep only the elements with even-numbered keys.
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/// map.retain(|&k, _| k % 2 == 0);
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/// assert!(map.into_iter().eq(vec![(0, 0), (2, 20), (4, 40), (6, 60)]));
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/// ```
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#[inline]
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#[unstable(feature = "btree_retain", issue = "79025")]
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pub fn retain<F>(&mut self, mut f: F)
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where
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F: FnMut(&K, &mut V) -> bool,
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{
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self.drain_filter(|k, v| !f(k, v));
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}
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/// Moves all elements from `other` into `Self`, leaving `other` empty.
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///
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/// # Examples
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@ -808,6 +808,17 @@ fn test_range_mut() {
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map.check();
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}
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#[test]
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fn test_retain() {
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let mut map: BTreeMap<i32, i32> = (0..100).map(|x| (x, x * 10)).collect();
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map.retain(|&k, _| k % 2 == 0);
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assert_eq!(map.len(), 50);
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assert_eq!(map[&2], 20);
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assert_eq!(map[&4], 40);
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assert_eq!(map[&6], 60);
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}
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mod test_drain_filter {
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use super::*;
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@ -798,6 +798,30 @@ impl<T: Ord> BTreeSet<T> {
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Recover::take(&mut self.map, value)
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}
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/// Retains only the elements specified by the predicate.
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///
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/// In other words, remove all elements `e` such that `f(&e)` returns `false`.
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///
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/// # Examples
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///
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/// ```
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/// #![feature(btree_retain)]
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/// use std::collections::BTreeSet;
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///
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/// let xs = [1, 2, 3, 4, 5, 6];
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/// let mut set: BTreeSet<i32> = xs.iter().cloned().collect();
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/// // Keep only the even numbers.
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/// set.retain(|&k| k % 2 == 0);
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/// assert!(set.iter().eq([2, 4, 6].iter()));
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/// ```
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#[unstable(feature = "btree_retain", issue = "79025")]
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pub fn retain<F>(&mut self, mut f: F)
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where
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F: FnMut(&T) -> bool,
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{
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self.drain_filter(|v| !f(v));
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}
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/// Moves all elements from `other` into `Self`, leaving `other` empty.
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///
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/// # Examples
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@ -324,6 +324,17 @@ fn test_is_subset() {
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assert_eq!(is_subset(&[99, 100], &large), false);
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}
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#[test]
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fn test_retain() {
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let xs = [1, 2, 3, 4, 5, 6];
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let mut set: BTreeSet<i32> = xs.iter().cloned().collect();
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set.retain(|&k| k % 2 == 0);
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assert_eq!(set.len(), 3);
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assert!(set.contains(&2));
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assert!(set.contains(&4));
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assert!(set.contains(&6));
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}
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#[test]
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fn test_drain_filter() {
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let mut x: BTreeSet<_> = [1].iter().copied().collect();
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