Implement ZipEq::fold

Author: kinto-b

src/zip_eq_impl.rs

@@ -52,6 +52,20 @@ where
         }
     }
 
+    #[inline]
+    fn fold<B, F>(self, init: B, mut f: F) -> B
+    where
+        Self: Sized,
+        F: FnMut(B, Self::Item) -> B,
+    {
+        let Self { a, mut b } = self;
+
+        a.fold(init, |acc, x| match b.next() {
+            Some(y) => f(acc, (x, y)),
+            None => panic!("itertools: .zip_eq() reached end of one iterator before the other"),
+        })
+    }
+
     fn size_hint(&self) -> (usize, Option<usize>) {
         size_hint::min(self.a.size_hint(), self.b.size_hint())
     }