Add finite iterator specialisations for Cycle

Author: varkor

src/libcore/iter/mod.rs

@@ -302,7 +302,7 @@
 
 #![stable(feature = "rust1", since = "1.0.0")]
 
-use cmp;
+use cmp::{self, Ordering};
 use fmt;
 use iter_private::TrustedRandomAccess;
 use ops::Try;
@@ -643,6 +643,41 @@ impl<I> Iterator for Cycle<I> where I: Clone + Iterator {
             _ => (usize::MAX, None)
         }
     }
+
+    #[inline]
+    fn all<F>(&mut self, f: F) -> bool where F: FnMut(Self::Item) -> bool { self.orig.clone().all(f) }
+
+    #[inline]
+    fn max(self) -> Option<Self::Item> where Self::Item: cmp::Ord { self.orig.clone().max() }
+
+    #[inline]
+    fn min(self) -> Option<Self::Item> where Self::Item: cmp::Ord {
+        cmp::min(self.iter.min(), self.orig.clone().min())
+    }
+
+    #[inline]
+    fn max_by_key<B: Ord, F>(self, f: F) -> Option<Self::Item>
+            where F: FnMut(&Self::Item) -> B {
+        self.orig.clone().max_by_key(f)
+    }
+
+    #[inline]
+    fn max_by<F>(self, f: F) -> Option<Self::Item>
+            where F: FnMut(&Self::Item, &Self::Item) -> Ordering {
+        self.orig.clone().max_by(f)
+    }
+
+    #[inline]
+    fn min_by_key<B: Ord, F>(self, f: F) -> Option<Self::Item>
+            where F: FnMut(&Self::Item) -> B {
+        self.iter.chain(self.orig.clone()).min_by_key(f)
+    }
+
+    #[inline]
+    fn min_by<F>(self, f: F) -> Option<Self::Item>
+            where F: FnMut(&Self::Item, &Self::Item) -> Ordering {
+        self.iter.chain(self.orig.clone()).min_by(f)
+    }
 }
 
 #[unstable(feature = "fused", issue = "35602")]

src/libcore/tests/iter.rs

@@ -867,6 +867,20 @@ fn test_cycle() {
     assert_eq!(it.next(), None);
 }
 
+#[test]
+fn test_cycle_iterator() {
+    let a = 1;
+    let b = 5;
+    let mut it = (a..b).cycle();
+    assert_eq!(it.all(|x| x <= b), true);
+    assert_eq!((a..b).cycle().max(), Some(b - 1));
+    assert_eq!((a..b).cycle().min(), Some(a));
+    assert_eq!((a..b).cycle().max_by_key(|x| -x), Some(a));
+    assert_eq!((a..b).cycle().max_by(|x, y| y.cmp(x)), Some(a));
+    assert_eq!((a..b).cycle().min_by_key(|x| -x), Some(b - 1));
+    assert_eq!((a..b).cycle().min_by(|x, y| y.cmp(x)), Some(b - 1));
+}
+
 #[test]
 fn test_iterator_nth() {
     let v: &[_] = &[0, 1, 2, 3, 4];
@@ -1414,9 +1428,9 @@ fn test_repeat_iterator() {
     assert_eq!(repeat(42).max(), Some(42));
     assert_eq!(repeat(42).min(), Some(42));
     assert_eq!(repeat(42).max_by_key(|_| 0), Some(42));
-    assert_eq!(repeat(42).max_by_key(|_| Ordering::Greater), Some(42));
+    assert_eq!(repeat(42).max_by(|_, _| Ordering::Equal), Some(42));
     assert_eq!(repeat(42).min_by_key(|_| 0), Some(42));
-    assert_eq!(repeat(42).min_by_key(|_| Ordering::Greater), Some(42));
+    assert_eq!(repeat(42).min_by(|_, _| Ordering::Equal), Some(42));
 }
 
 #[test]