tactics/ladder.h

   1 #ifndef PACHI_TACTICS_LADDER_H
   2 #define PACHI_TACTICS_LADDER_H
   3
   4 /* Reading ladders. */
   5
   6 #include "board.h"
   7 #include "debug.h"
   8
   9 /* Check if escaping on this liberty by given group in atari would play out
  10  * a simple ladder. */
  11 /* Two ways of ladder reading can be enabled separately; simple first-line
  12  * ladders and trivial middle-board ladders. */
  13 static bool is_ladder(struct board *b, coord_t coord, group_t laddered, bool test_middle);
  14
  15 /* Check if a 2-lib group of color @lcolor escaping at @escapelib would be
  16  * caught in a ladder given opponent stone at @chaselib.  */
  17 bool wouldbe_ladder(struct board *b, group_t group, coord_t escapelib, coord_t chaselib, enum stone lcolor);
  18
  19
  20 bool is_border_ladder(struct board *b, coord_t coord, enum stone lcolor);
  21 bool is_middle_ladder(struct board *b, coord_t coord, group_t group, enum stone lcolor);
  22 static inline bool
  23 is_ladder(struct board *b, coord_t coord, group_t laddered, bool test_middle)
  24 {
  25         enum stone lcolor = board_at(b, group_base(laddered));
  26
  27         if (DEBUGL(6))
  28                 fprintf(stderr, "ladder check - does %s play out %s's laddered group %s?\n",
  29                         coord2sstr(coord, b), stone2str(lcolor), coord2sstr(laddered, b));
  30
  31         /* First, special-case first-line "ladders". This is a huge chunk
  32          * of ladders we actually meet and want to play. */
  33         if (neighbor_count_at(b, coord, S_OFFBOARD) == 1
  34             && neighbor_count_at(b, coord, lcolor) == 1) {
  35                 bool l = is_border_ladder(b, coord, lcolor);
  36                 if (DEBUGL(6)) fprintf(stderr, "border ladder solution: %d\n", l);
  37                 return l;
  38         }
  39
  40         bool l = test_middle && is_middle_ladder(b, coord, laddered, lcolor);
  41         if (DEBUGL(6)) fprintf(stderr, "middle ladder solution: %d\n", l);
  42         return l;
  43 }
  44
  45 #endif