tactics/ladder.h

   1 #ifndef ZZGO_TACTICS_LADDER_H
   2 #define ZZGO_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,
  14                       bool border_ladders, bool middle_ladders);
  15
  16
  17 bool is_border_ladder(struct board *b, coord_t coord, enum stone lcolor);
  18 bool is_middle_ladder(struct board *b, coord_t coord, enum stone lcolor);
  19 static inline bool
  20 is_ladder(struct board *b, coord_t coord, group_t laddered,
  21           bool border_ladders, bool middle_ladders)
  22 {
  23         enum stone lcolor = board_at(b, group_base(laddered));
  24
  25         if (DEBUGL(6))
  26                 fprintf(stderr, "ladder check - does %s play out %s's laddered group %s?\n",
  27                         coord2sstr(coord, b), stone2str(lcolor), coord2sstr(laddered, b));
  28
  29         /* First, special-case first-line "ladders". This is a huge chunk
  30          * of ladders we actually meet and want to play. */
  31         if (border_ladders
  32             && neighbor_count_at(b, coord, S_OFFBOARD) == 1
  33             && neighbor_count_at(b, coord, lcolor) == 1) {
  34                 bool l = is_border_ladder(b, coord, lcolor);
  35                 if (DEBUGL(6)) fprintf(stderr, "border ladder solution: %d\n", l);
  36                 return l;
  37         }
  38
  39         if (middle_ladders) {
  40                 bool l = is_middle_ladder(b, coord, lcolor);
  41                 if (DEBUGL(6)) fprintf(stderr, "middle ladder solution: %d\n", l);
  42                 return l;
  43         }
  44
  45         if (DEBUGL(6)) fprintf(stderr, "no ladder to be checked\n");
  46         return false;
  47 }
  48
  49 #endif