Specialize RepeatN::[r]fold

src/repeatn.rs

@@ -44,6 +44,20 @@ where
     fn size_hint(&self) -> (usize, Option<usize>) {
         (self.n, Some(self.n))
     }
+
+    fn fold<B, F>(self, mut init: B, mut f: F) -> B
+    where
+        F: FnMut(B, Self::Item) -> B,
+    {
+        match self {
+            Self { elt: Some(elt), n } => {
+                debug_assert!(n > 0);
+                init = (1..n).map(|_| elt.clone()).fold(init, &mut f);
+                f(init, elt)
+            }
+            _ => init,
+        }
+    }
 }
 
 impl<A> DoubleEndedIterator for RepeatN<A>
@@ -54,6 +68,14 @@ where
     fn next_back(&mut self) -> Option<Self::Item> {
         self.next()
     }
+
+    #[inline]
+    fn rfold<B, F>(self, init: B, f: F) -> B
+    where
+        F: FnMut(B, Self::Item) -> B,
+    {
+        self.fold(init, f)
+    }
 }
 
 impl<A> ExactSizeIterator for RepeatN<A> where A: Clone {}