-/* Return yx_uint16 coordinate one step from coordinate yx in direction dir. */
-extern struct yx_uint16 mv_yx_in_dir(enum dir d, struct yx_uint16 yx);
+
+
+/* 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);
+
+