1 files changed, 60 insertions, 0 deletions
diff --git a/src/zip_eq_impl.rs b/src/zip_eq_impl.rs
new file mode 100644
index 0000000..857465d
--- /dev/null
+++ b/src/zip_eq_impl.rs
@@ -0,0 +1,60 @@
+use super::size_hint;
+
+/// An iterator which iterates two other iterators simultaneously
+///
+/// See [`.zip_eq()`](../trait.Itertools.html#method.zip_eq) for more information.
+#[derive(Clone, Debug)]
+#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
+pub struct ZipEq<I, J> {
+    a: I,
+    b: J,
+}
+
+/// Iterate `i` and `j` in lock step.
+///
+/// **Panics** if the iterators are not of the same length.
+///
+/// `IntoIterator` enabled version of `i.zip_eq(j)`.
+///
+/// ```
+/// use itertools::zip_eq;
+///
+/// let data = [1, 2, 3, 4, 5];
+/// for (a, b) in zip_eq(&data[..data.len() - 1], &data[1..]) {
+///     /* loop body */
+/// }
+/// ```
+pub fn zip_eq<I, J>(i: I, j: J) -> ZipEq<I::IntoIter, J::IntoIter>
+    where I: IntoIterator,
+          J: IntoIterator
+{
+    ZipEq {
+        a: i.into_iter(),
+        b: j.into_iter(),
+    }
+}
+
+impl<I, J> Iterator for ZipEq<I, J>
+    where I: Iterator,
+          J: Iterator
+{
+    type Item = (I::Item, J::Item);
+
+    fn next(&mut self) -> Option<Self::Item> {
+        match (self.a.next(), self.b.next()) {
+            (None, None) => None,
+            (Some(a), Some(b)) => Some((a, b)),
+            (None, Some(_)) | (Some(_), 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())
+    }
+}
+
+impl<I, J> ExactSizeIterator for ZipEq<I, J>
+    where I: ExactSizeIterator,
+          J: ExactSizeIterator
+{}