Introduce the GroupBy and GroupByMut Iterators

4 files changed, 31 insertions, 0 deletions

diff --git a/library/alloc/src/lib.rs b/library/alloc/src/lib.rs
index 3ac34c9ae28..34102d9c403 100644
--- a/library/alloc/src/lib.rs
+++ b/library/alloc/src/lib.rs
@@ -140,6 +140,7 @@
 #![feature(try_trait)]
 #![feature(type_alias_impl_trait)]
 #![feature(associated_type_bounds)]
+#![feature(slice_group_by)]
 // Allow testing this library
 
 #[cfg(test)]
diff --git a/library/alloc/src/slice.rs b/library/alloc/src/slice.rs
index 064700fc72c..bfa317ffd73 100644
--- a/library/alloc/src/slice.rs
+++ b/library/alloc/src/slice.rs
@@ -118,6 +118,8 @@ pub use core::slice::{RChunks, RChunksExact, RChunksExactMut, RChunksMut};
 pub use core::slice::{RSplit, RSplitMut};
 #[stable(feature = "rust1", since = "1.0.0")]
 pub use core::slice::{RSplitN, RSplitNMut, SplitN, SplitNMut};
+#[unstable(feature = "slice_group_by", issue = "0")]
+pub use core::slice::{GroupBy, GroupByMut};
 
 ////////////////////////////////////////////////////////////////////////////////
 // Basic slice extension methods
diff --git a/library/alloc/tests/lib.rs b/library/alloc/tests/lib.rs
index b7cc03f8eb9..268153242c7 100644
--- a/library/alloc/tests/lib.rs
+++ b/library/alloc/tests/lib.rs
@@ -21,6 +21,7 @@
 #![feature(iter_map_while)]
 #![feature(int_bits_const)]
 #![feature(vecdeque_binary_search)]
+#![feature(slice_group_by)]
 
 use std::collections::hash_map::DefaultHasher;
 use std::hash::{Hash, Hasher};
diff --git a/library/alloc/tests/slice.rs b/library/alloc/tests/slice.rs
index a4f0fb415fb..e2fdb5a6b5a 100644
--- a/library/alloc/tests/slice.rs
+++ b/library/alloc/tests/slice.rs
@@ -1898,3 +1898,30 @@ fn subslice_patterns() {
     m!(&mut v, [..] => ());
     m!(&mut v, [x, .., y] => c!((x, y), (&mut N, &mut N), (&mut N(0), &mut N(4))));
 }
+
+#[test]
+fn test_group_by() {
+    let slice = &[1, 1, 1, 3, 3, 2, 2, 2];
+
+    let mut iter = slice.group_by(|a, b| a == b);
+
+    assert_eq!(iter.next(), Some(&[1, 1, 1][..]));
+
+    assert_eq!(iter.remaining(), &[3, 3, 2, 2, 2]);
+
+    assert_eq!(iter.next(), Some(&[3, 3][..]));
+    assert_eq!(iter.next(), Some(&[2, 2, 2][..]));
+    assert_eq!(iter.next(), None);
+}
+
+#[test]
+fn test_group_by_rev() {
+    let slice = &[1, 1, 1, 3, 3, 2, 2, 2];
+
+    let mut iter = slice.group_by(|a, b| a == b);
+
+    assert_eq!(iter.next_back(), Some(&[2, 2, 2][..]));
+    assert_eq!(iter.next_back(), Some(&[3, 3][..]));
+    assert_eq!(iter.next_back(), Some(&[1, 1, 1][..]));
+    assert_eq!(iter.next_back(), None);
+}