-/* Update game log by appending "text", or by appending a "." if "text" is the
- * same as the last one passed.
- */
-extern void update_log(struct World * world, char * text);
-
-
-
-/* Return the offset necessary to center "map" on position "pos" in a frame of
- * "framesize.
- */
-extern uint16_t center_offset(uint16_t pos, uint16_t mapsize,
- uint16_t framesize);
-
-
-
-/* Record last player "action" in game record file "record, increment the game
- * turn and trigger enemy movement.
- */
-extern void turn_over(struct World * world, char action);
+/* If one and only one of files at "p1", "p2" exists, fail with explanation. */
+extern void check_files_xor(char * p1, char * p2);