tactics/dragon.h

   1 #ifndef PACHI_TACTICS_DRAGON_H
   2 #define PACHI_TACTICS_DRAGON_H
   3
   4 /* Functions for dealing with dragons, ie virtually connected groups of stones.
   5  * Used for some high-level tactics decisions, like trying to detect useful lost
   6  * ladders or whether breaking a 3-stones seki is safe.
   7  * Currently these are fairly expensive (dragon data is not cached) so shouldn't be
   8  * called by low-level / perf-critical code. */
   9
  10
  11 /* Like group_at() but returns unique id for all stones in a dragon.
  12  * Depending on the situation what is considered to be a dragon here may or
  13  * may not match what we'd intuitively call a dragon: there are connections
  14  * it doesn't understand (dead cutting stones for instance) so it'll usually
  15  * be smaller. Doesn't need to be perfect though. */
  16 group_t dragon_at(struct board *b, coord_t to);
  17
  18 /* Returns total number of liberties of dragon at @to. */
  19 int dragon_liberties(struct board *b, enum stone color, coord_t to);
  20
  21 /* Print board highlighting given dragon */
  22 void dragon_print(struct board *board, FILE *f, group_t dragon);
  23
  24 /* Like board_print() but use a different color for each dragon */
  25 void board_print_dragons(struct board *board, FILE *f);
  26
  27 /* Pick a color for dragon with index @i. Returns ansi color code.
  28  * Useful for writing custom board_print_dragons()-like functions. */
  29 char *pick_dragon_color(int i, bool bold, bool white_ok);
  30
  31 /* Try to find out if dragon has 2 eyes. Pretty conservative:
  32  * big eye areas are counted as one eye, must be completely enclosed and
  33  * have all surrounded stones connected. Doesn't need to be perfect though. */
  34 bool dragon_is_safe(struct board *b, group_t g, enum stone color);
  35
  36 /* Like group_is_safe() but passing already visited stones / eyes. */
  37 bool dragon_is_safe_full(struct board *b, group_t g, enum stone color, int *visited, int *eyes);
  38
  39 /* Try to detect big eye area, ie:
  40  *  - completely enclosed area, not too big,
  41  *  - surrounding stones all connected to each other
  42  *  - size >= 2  (so no false eye issues)
  43  * Returns size of the area, or 0 if doesn't match.  */
  44 int big_eye_area(struct board *b, enum stone color, coord_t around, int *visited);
  45
  46 /* Try to find out if dragon is completely surrounded:
  47  * Look for outwards 2-stones gap from our external liberties.
  48  * (hack, but works pretty well in practice) */
  49 bool dragon_is_surrounded(struct board *b, coord_t to);
  50
  51
  52 #endif /* PACHI_TACTICS_DRAGON_H */