-/* Return 1 if two yx_uint16 coordinates a and b are equal, else 0. */
-extern char yx_uint16_cmp(struct yx_uint16 a, struct yx_uint16 b);
+/* Return 1 if two yx_uint16 coordinates at "a" and "b" are equal, else 0. */
+extern uint8_t yx_uint16_cmp(struct yx_uint16 * a, struct yx_uint16 * b);
+
+
+
+/* Return yx_uint16 coordinate one step from coordinate yx in direction "dir"
+ * (east: 'E', west: 'W', north: 'N', south: 'S').
+ *
+ * If an invalid dir "d" is passed, "yx" remains unchanged.
+ */
+extern struct yx_uint16 mv_yx_in_dir(char dir, struct yx_uint16 yx);
+