grid: add find_all method/iterator

utils/grid/lib.rs

@@ -361,6 +361,13 @@ impl<T: Clone + Eq + PartialEq + Debug> Grid<T> {
                 .unwrap_or(-1),
         )
     }
+    /// Get all of the coordinates having value `needle`
+    pub fn find_all<'a>(&'a self, needle: &'a T) -> impl Iterator<Item = Coord2d> + 'a {
+        self.data
+            .iter()
+            .enumerate()
+            .filter_map(|(pos, val)| (*val == *needle).then_some(self.coord(pos as i64).unwrap()))
+    }
     pub fn count(&self, haystack: &T) -> usize {
         self.data.iter().filter(|item| *item == haystack).count()
     }
@@ -566,6 +573,15 @@ FBCG";
         assert!(grid.col_iter(4).is_none());
     }
 
+    #[test]
+    fn find_all() {
+        let grid = unchecked_load();
+        assert_eq!(
+            grid.find_all(&b'G').collect::<Vec<_>>(),
+            [Coord2d { x: 2, y: 1 }, Coord2d { x: 3, y: 3 }]
+        )
+    }
+
     // #[test]
     // fn window_compare() {
     //     let grid = unchecked_load();