1 files changed, 20 insertions, 0 deletions
diff --git a/src/math.rs b/src/math.rs
index ce9d885..da06622 100644
--- a/src/math.rs
+++ b/src/math.rs
@@ -131,4 +131,24 @@ impl Point {
             (dx == 1 && dy == 0)
         
     }
+
+    pub fn is_on_lattice(&self, lattice_size: u16) -> bool {
+        (self.x + self.y) % lattice_size == 0
+    }
+}
+
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    
+    #[test]
+    fn point_on_lattice_works() {
+        assert_eq!(true, Point::new(0,0).is_on_lattice(4));
+        assert_eq!(true, Point::new(4,0).is_on_lattice(4));
+        assert_eq!(true, Point::new(0,4).is_on_lattice(4));
+        assert_eq!(true, Point::new(4,4).is_on_lattice(4));
+        assert_eq!(true, Point::new(1,3).is_on_lattice(4));
+        assert_eq!(true, Point::new(3,1).is_on_lattice(4));        
+    }
 }