+
+#include <stdint.h> /* for uint8_t, uint16_t */
+
+
+
+/* Coordinates for maps of max. 65536x65536 cells. */
+struct yx_uint16
+{
+ uint16_t y;
+ uint16_t x;
+};
+
+/* Directions available for movement. */
+enum dir
+{
+ NORTH = 1,
+ EAST,
+ SOUTH,
+ WEST
+};
+
+/* Return 1 if two yx_uint16 coordinates 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. */
+extern struct yx_uint16 mv_yx_in_dir(enum dir d, struct yx_uint16 yx);