1 files changed, 13 insertions, 0 deletions
diff --git a/2024_rust/src/lib.rs b/2024_rust/src/lib.rs
index c034fea..ea6f7d6 100644
--- a/2024_rust/src/lib.rs
+++ b/2024_rust/src/lib.rs
@@ -1,5 +1,6 @@
 pub mod matrix {
     pub type Pos = (usize, usize);
+    pub type PosDelta = (isize, isize);
 
     #[derive(Clone)]
     pub struct Matrix<T> {
@@ -27,6 +28,18 @@ pub mod matrix {
         pub fn set(&mut self, (x, y): Pos, dot: T) {
             self.dots[x][y] = dot;
         }
+
+        pub fn pos_move(&self, (x, y): Pos, (dx, dy): PosDelta) -> Option<Pos> {
+            let x2 = x as isize + dx;
+            if x2 < 0 || x2 >= self.limit.0 as isize {
+                return None;
+            }
+            let y2 = y as isize + dy;
+            if y2 < 0 || y2 >= self.limit.1 as isize {
+                return None;
+            }
+            Some((x2 as usize, y2 as usize))
+        }
     }
 
     use std::fmt;