Rollup merge of #70850 - ssomers:btreemap_first_last, r=Amanieu
BTreeMap first last proposal tweaks Clean-up and following up on a request in #62924. Trying the reviewer of the original code #65637... r? @scottmcm
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b9bb12640e
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@ -653,11 +653,7 @@ impl<K: Ord, V> BTreeMap<K, V> {
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/// assert_eq!(map.first_key_value(), Some((&1, &"b")));
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/// ```
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#[unstable(feature = "map_first_last", issue = "62924")]
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pub fn first_key_value<T: ?Sized>(&self) -> Option<(&K, &V)>
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where
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T: Ord,
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K: Borrow<T>,
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{
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pub fn first_key_value(&self) -> Option<(&K, &V)> {
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let front = self.root.as_ref()?.as_ref().first_leaf_edge();
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front.right_kv().ok().map(Handle::into_kv)
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}
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@ -667,7 +663,38 @@ impl<K: Ord, V> BTreeMap<K, V> {
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///
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/// # Examples
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///
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/// Contrived way to `clear` a map:
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/// ```
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/// #![feature(map_first_last)]
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/// use std::collections::BTreeMap;
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///
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/// let mut map = BTreeMap::new();
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/// map.insert(1, "a");
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/// map.insert(2, "b");
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/// if let Some(mut entry) = map.first_entry() {
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/// if *entry.key() > 0 {
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/// entry.insert("first");
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/// }
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/// }
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/// assert_eq!(*map.get(&1).unwrap(), "first");
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/// assert_eq!(*map.get(&2).unwrap(), "b");
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/// ```
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#[unstable(feature = "map_first_last", issue = "62924")]
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pub fn first_entry(&mut self) -> Option<OccupiedEntry<'_, K, V>> {
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let front = self.root.as_mut()?.as_mut().first_leaf_edge();
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let kv = front.right_kv().ok()?;
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Some(OccupiedEntry {
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handle: kv.forget_node_type(),
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length: &mut self.length,
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_marker: PhantomData,
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})
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}
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/// Removes and returns the first element in the map.
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/// The key of this element is the minimum key that was in the map.
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///
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/// # Examples
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///
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/// Draining elements in ascending order, while keeping a usable map each iteration.
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///
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/// ```
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/// #![feature(map_first_last)]
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@ -676,27 +703,14 @@ impl<K: Ord, V> BTreeMap<K, V> {
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/// let mut map = BTreeMap::new();
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/// map.insert(1, "a");
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/// map.insert(2, "b");
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/// while let Some(entry) = map.first_entry() {
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/// let (key, val) = entry.remove_entry();
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/// assert!(!map.contains_key(&key));
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/// while let Some((key, _val)) = map.pop_first() {
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/// assert!(map.iter().all(|(k, _v)| *k > key));
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/// }
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/// assert!(map.is_empty());
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/// ```
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#[unstable(feature = "map_first_last", issue = "62924")]
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pub fn first_entry<T: ?Sized>(&mut self) -> Option<OccupiedEntry<'_, K, V>>
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where
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T: Ord,
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K: Borrow<T>,
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{
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let front = self.root.as_mut()?.as_mut().first_leaf_edge();
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if let Ok(kv) = front.right_kv() {
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Some(OccupiedEntry {
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handle: kv.forget_node_type(),
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length: &mut self.length,
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_marker: PhantomData,
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})
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} else {
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None
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}
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pub fn pop_first(&mut self) -> Option<(K, V)> {
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self.first_entry().map(|entry| entry.remove_entry())
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}
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/// Returns the last key-value pair in the map.
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@ -716,11 +730,7 @@ impl<K: Ord, V> BTreeMap<K, V> {
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/// assert_eq!(map.last_key_value(), Some((&2, &"a")));
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/// ```
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#[unstable(feature = "map_first_last", issue = "62924")]
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pub fn last_key_value<T: ?Sized>(&self) -> Option<(&K, &V)>
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where
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T: Ord,
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K: Borrow<T>,
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{
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pub fn last_key_value(&self) -> Option<(&K, &V)> {
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let back = self.root.as_ref()?.as_ref().last_leaf_edge();
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back.left_kv().ok().map(Handle::into_kv)
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}
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@ -730,7 +740,38 @@ impl<K: Ord, V> BTreeMap<K, V> {
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///
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/// # Examples
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///
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/// Contrived way to `clear` a map:
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/// ```
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/// #![feature(map_first_last)]
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/// use std::collections::BTreeMap;
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///
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/// let mut map = BTreeMap::new();
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/// map.insert(1, "a");
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/// map.insert(2, "b");
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/// if let Some(mut entry) = map.last_entry() {
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/// if *entry.key() > 0 {
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/// entry.insert("last");
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/// }
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/// }
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/// assert_eq!(*map.get(&1).unwrap(), "a");
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/// assert_eq!(*map.get(&2).unwrap(), "last");
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/// ```
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#[unstable(feature = "map_first_last", issue = "62924")]
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pub fn last_entry(&mut self) -> Option<OccupiedEntry<'_, K, V>> {
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let back = self.root.as_mut()?.as_mut().last_leaf_edge();
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let kv = back.left_kv().ok()?;
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Some(OccupiedEntry {
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handle: kv.forget_node_type(),
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length: &mut self.length,
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_marker: PhantomData,
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})
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}
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/// Removes and returns the last element in the map.
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/// The key of this element is the maximum key that was in the map.
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///
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/// # Examples
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///
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/// Draining elements in descending order, while keeping a usable map each iteration.
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///
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/// ```
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/// #![feature(map_first_last)]
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@ -739,27 +780,14 @@ impl<K: Ord, V> BTreeMap<K, V> {
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/// let mut map = BTreeMap::new();
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/// map.insert(1, "a");
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/// map.insert(2, "b");
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/// while let Some(entry) = map.last_entry() {
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/// let (key, val) = entry.remove_entry();
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/// assert!(!map.contains_key(&key));
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/// while let Some((key, _val)) = map.pop_last() {
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/// assert!(map.iter().all(|(k, _v)| *k < key));
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/// }
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/// assert!(map.is_empty());
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/// ```
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#[unstable(feature = "map_first_last", issue = "62924")]
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pub fn last_entry<T: ?Sized>(&mut self) -> Option<OccupiedEntry<'_, K, V>>
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where
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T: Ord,
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K: Borrow<T>,
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{
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let back = self.root.as_mut()?.as_mut().last_leaf_edge();
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if let Ok(kv) = back.left_kv() {
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Some(OccupiedEntry {
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handle: kv.forget_node_type(),
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length: &mut self.length,
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_marker: PhantomData,
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})
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} else {
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None
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}
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pub fn pop_last(&mut self) -> Option<(K, V)> {
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self.last_entry().map(|entry| entry.remove_entry())
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}
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/// Returns `true` if the map contains a value for the specified key.
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