1 files changed, 65 insertions, 0 deletions
diff --git a/src/iter.rs b/src/iter.rs
new file mode 100644
index 0000000..650dceb
--- /dev/null
+++ b/src/iter.rs
@@ -0,0 +1,65 @@
+use std::fmt::Debug;
+use std::iter::Peekable;
+
+pub trait IteratorExt: Sized + Iterator
+{
+    /// Returns an iterator over overlapping item tuples.
+    fn windows(self) -> Windows<Self>;
+}
+
+impl<Iter: Iterator> IteratorExt for Iter
+where
+    Iter::Item: Clone,
+{
+    fn windows(self) -> Windows<Self>
+    {
+        Windows {
+            iter: self.peekable(),
+        }
+    }
+}
+
+pub struct Windows<Iter: Iterator>
+{
+    iter: Peekable<Iter>,
+}
+
+impl<Iter: Iterator> Iterator for Windows<Iter>
+where
+    Iter::Item: Clone + Debug,
+{
+    type Item = (Iter::Item, Option<Iter::Item>);
+
+    fn next(&mut self) -> Option<Self::Item>
+    {
+        let opt_first = self.iter.next();
+        let opt_second = self.iter.peek();
+
+        let Some(first) = opt_first else {
+            return None;
+        };
+
+        Some((first, opt_second.cloned()))
+    }
+}
+
+#[cfg(test)]
+mod tests
+{
+    use pretty_assertions::assert_eq;
+
+    use super::*;
+
+    #[test]
+    fn windows_works()
+    {
+        let mut windows = (0..6).windows();
+
+        assert_eq!(windows.next(), Some((0, Some(1))));
+        assert_eq!(windows.next(), Some((1, Some(2))));
+        assert_eq!(windows.next(), Some((2, Some(3))));
+        assert_eq!(windows.next(), Some((3, Some(4))));
+        assert_eq!(windows.next(), Some((4, Some(5))));
+        assert_eq!(windows.next(), Some((5, None)));
+    }
+}