Shortcuts for min/max on ordinary BTreeMap/BTreeSet iterators

2 files changed, 75 insertions, 0 deletions

diff --git a/src/liballoc/collections/btree/map.rs b/src/liballoc/collections/btree/map.rs
index 34cacebe796..bb9091a6659 100644
--- a/src/liballoc/collections/btree/map.rs
+++ b/src/liballoc/collections/btree/map.rs
@@ -1396,6 +1396,14 @@ impl<'a, K: 'a, V: 'a> Iterator for Iter<'a, K, V> {
     fn last(mut self) -> Option<(&'a K, &'a V)> {
         self.next_back()
     }
+
+    fn min(mut self) -> Option<(&'a K, &'a V)> {
+        self.next()
+    }
+
+    fn max(mut self) -> Option<(&'a K, &'a V)> {
+        self.next_back()
+    }
 }
 
 #[stable(feature = "fused", since = "1.26.0")]
@@ -1458,6 +1466,14 @@ impl<'a, K: 'a, V: 'a> Iterator for IterMut<'a, K, V> {
     fn last(mut self) -> Option<(&'a K, &'a mut V)> {
         self.next_back()
     }
+
+    fn min(mut self) -> Option<(&'a K, &'a mut V)> {
+        self.next()
+    }
+
+    fn max(mut self) -> Option<(&'a K, &'a mut V)> {
+        self.next_back()
+    }
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
@@ -1595,6 +1611,14 @@ impl<'a, K, V> Iterator for Keys<'a, K, V> {
     fn last(mut self) -> Option<&'a K> {
         self.next_back()
     }
+
+    fn min(mut self) -> Option<&'a K> {
+        self.next()
+    }
+
+    fn max(mut self) -> Option<&'a K> {
+        self.next_back()
+    }
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
@@ -1768,6 +1792,14 @@ impl<'a, K, V> Iterator for Range<'a, K, V> {
     fn last(mut self) -> Option<(&'a K, &'a V)> {
         self.next_back()
     }
+
+    fn min(mut self) -> Option<(&'a K, &'a V)> {
+        self.next()
+    }
+
+    fn max(mut self) -> Option<(&'a K, &'a V)> {
+        self.next_back()
+    }
 }
 
 #[stable(feature = "map_values_mut", since = "1.10.0")]
@@ -1853,6 +1885,14 @@ impl<'a, K, V> Iterator for RangeMut<'a, K, V> {
     fn last(mut self) -> Option<(&'a K, &'a mut V)> {
         self.next_back()
     }
+
+    fn min(mut self) -> Option<(&'a K, &'a mut V)> {
+        self.next()
+    }
+
+    fn max(mut self) -> Option<(&'a K, &'a mut V)> {
+        self.next_back()
+    }
 }
 
 impl<'a, K, V> RangeMut<'a, K, V> {
diff --git a/src/liballoc/collections/btree/set.rs b/src/liballoc/collections/btree/set.rs
index 525ef38c32f..d8959966fe5 100644
--- a/src/liballoc/collections/btree/set.rs
+++ b/src/liballoc/collections/btree/set.rs
@@ -1291,12 +1291,22 @@ impl<'a, T> Iterator for Iter<'a, T> {
     fn next(&mut self) -> Option<&'a T> {
         self.iter.next()
     }
+
     fn size_hint(&self) -> (usize, Option<usize>) {
         self.iter.size_hint()
     }
+
     fn last(mut self) -> Option<&'a T> {
         self.next_back()
     }
+
+    fn min(mut self) -> Option<&'a T> {
+        self.next()
+    }
+
+    fn max(mut self) -> Option<&'a T> {
+        self.next_back()
+    }
 }
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<'a, T> DoubleEndedIterator for Iter<'a, T> {
@@ -1321,6 +1331,7 @@ impl<T> Iterator for IntoIter<T> {
     fn next(&mut self) -> Option<T> {
         self.iter.next().map(|(k, _)| k)
     }
+
     fn size_hint(&self) -> (usize, Option<usize>) {
         self.iter.size_hint()
     }
@@ -1359,6 +1370,14 @@ impl<'a, T> Iterator for Range<'a, T> {
     fn last(mut self) -> Option<&'a T> {
         self.next_back()
     }
+
+    fn min(mut self) -> Option<&'a T> {
+        self.next()
+    }
+
+    fn max(mut self) -> Option<&'a T> {
+        self.next_back()
+    }
 }
 
 #[stable(feature = "btree_range", since = "1.17.0")]
@@ -1429,6 +1448,10 @@ impl<'a, T: Ord> Iterator for Difference<'a, T> {
         };
         (self_len.saturating_sub(other_len), Some(self_len))
     }
+
+    fn min(mut self) -> Option<&'a T> {
+        self.next()
+    }
 }
 
 #[stable(feature = "fused", since = "1.26.0")]
@@ -1460,6 +1483,10 @@ impl<'a, T: Ord> Iterator for SymmetricDifference<'a, T> {
         // the number of elements to less than half the range of usize.
         (0, Some(a_len + b_len))
     }
+
+    fn min(mut self) -> Option<&'a T> {
+        self.next()
+    }
 }
 
 #[stable(feature = "fused", since = "1.26.0")]
@@ -1516,6 +1543,10 @@ impl<'a, T: Ord> Iterator for Intersection<'a, T> {
             IntersectionInner::Answer(Some(_)) => (1, Some(1)),
         }
     }
+
+    fn min(mut self) -> Option<&'a T> {
+        self.next()
+    }
 }
 
 #[stable(feature = "fused", since = "1.26.0")]
@@ -1541,6 +1572,10 @@ impl<'a, T: Ord> Iterator for Union<'a, T> {
         // No checked_add - see SymmetricDifference::size_hint.
         (max(a_len, b_len), Some(a_len + b_len))
     }
+
+    fn min(mut self) -> Option<&'a T> {
+        self.next()
+    }
 }
 
 #[stable(feature = "fused", since = "1.26.0")]