1 files changed, 19 insertions, 0 deletions
diff --git a/src/geom/align.rs b/src/geom/align.rs
index 239a6e70..69f32bee 100644
--- a/src/geom/align.rs
+++ b/src/geom/align.rs
@@ -183,3 +183,22 @@ impl Fold for GenAlign {
         self
     }
 }
+
+#[derive(Copy, Clone, Eq, PartialEq, Debug)]
+pub enum LeftRightAlternator {
+    Left,
+    Right,
+}
+
+impl Iterator for LeftRightAlternator {
+    type Item = LeftRightAlternator;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        let r = Some(*self);
+        match self {
+            Self::Left => *self = Self::Right,
+            Self::Right => *self = Self::Left,
+        }
+        r
+    }
+}