From f479cdd74dfe2f365c40d28f4e09c7f92a3c701f Mon Sep 17 00:00:00 2001
From: philipp <philipp>
Date: Tue, 11 Apr 2017 20:53:43 +0200
Subject: [PATCH] Add all_equal

---
 src/lib.rs     | 22 ++++++++++++++++++++++
 tests/tests.rs |  9 +++++++++
 2 files changed, 31 insertions(+)

diff --git a/src/lib.rs b/src/lib.rs
index 53e4971b5..654756758 100755
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -997,6 +997,28 @@ pub trait Itertools : Iterator {
         None
     }
 
+    /// Check whether all elements compare equal.
+    ///
+    /// Empty iterators are considered to have equal elements:
+    ///
+    /// ```
+    /// use itertools::Itertools;
+    ///
+    /// let data = vec![1, 1, 1, 2, 2, 3, 3, 3, 4, 5, 5];
+    /// assert!(!data.iter().all_equal());
+    /// assert!(data[0..3].iter().all_equal());
+    /// assert!(data[3..5].iter().all_equal());
+    /// assert!(data[5..8].iter().all_equal());
+    ///
+    /// let data : Option<usize> = None;
+    /// assert!(data.into_iter().all_equal());
+    /// ```
+    fn all_equal(&mut self) -> bool 
+        where Self::Item: PartialEq,
+    {
+        self.dedup().nth(1).is_none()
+    }
+
     /// Consume the first `n` elements from the iterator eagerly,
     /// and return the same iterator again.
     ///
diff --git a/tests/tests.rs b/tests/tests.rs
index b99980cae..de7caa9d5 100644
--- a/tests/tests.rs
+++ b/tests/tests.rs
@@ -185,6 +185,15 @@ fn dedup() {
     assert_eq!(&xs_d, &ys);
 }
 
+#[test]
+fn all_equal() {
+    assert!(!"AABBCCC".chars().all_equal());
+    assert!("AAAAAAA".chars().all_equal());
+    for (_key, mut sub) in &"AABBCCC".chars().group_by(|&x| x) {
+        assert!(sub.all_equal());
+    }
+}
+
 #[test]
 fn unique_by() {
     let xs = ["aaa", "bbbbb", "aa", "ccc", "bbbb", "aaaaa", "cccc"];