+extern struct yx_uint16 mv_yx_in_dir (char d, struct yx_uint16 yx) {
+// Return yx coordinates one step to the direction d of yx.
+ if (d == NORTH) yx.y--;
+ else if (d == EAST) yx.x++;
+ else if (d == SOUTH) yx.y++;
+ else if (d == WEST) yx.x--;
+ return yx; }
+