Fixed infinite recursion bug

pygo.py

@@ -7,6 +7,7 @@ import os
 import pygame
 from pygame.locals import *
 
+
 def load_png(name):
     """ Load image and return image object"""
     fullname = os.path.join('res', name)
@@ -55,6 +56,7 @@ class GobanSquare:
         self.x, self.y = pos
         self.state = -1
         self.marked = False
+        self.checked = False # Used for recursive checks
 
         if (self.x, self.y) == (1,1):
             self.default_draw_code = 'ul'
@@ -152,6 +154,8 @@ class Goban:
             if not self._has_liberties(p, who):
                 self.captures[self.turn] += self._delete_group(p)
 
+            self._clear_checks()
+
 
     def _valid_move(self, pos):
         x, y = pos
@@ -166,6 +170,7 @@ class Goban:
         self.board[x][y].state = self.turn
 
         liberties = self._has_liberties(pos, self.turn)
+        self._clear_checks()
 
         opponent = (self.turn + 1) % 2
 
@@ -174,7 +179,9 @@ class Goban:
             if not self._has_liberties(d, opponent):
                 kills_group = True
                 break
+            self._clear_checks()
 
+        # Remove temporary stone
         self.board[x][y].state = -1
 
         return liberties > 0 or kills_group
@@ -183,35 +190,26 @@ class Goban:
     # Recursively find whether there are liberties for the group
     # at pos. Positive numbers are not necessarily accurate - 
     # treat this as a boolean
-    # fixme: Apparently there is some case that causes infinite recursion,
-    # yay!
     def _has_liberties(self, pos, who, direction = None):
         x,y = pos
         if x < 0 or x > 18 or y < 0 or y > 18:
             return 0
 
         square = self.board[x][y]
+
+        if square.checked:
+            return 0
+        else:
+            square.checked = True
+
         if square.state == -1:
             return 1
         elif square.state != who:
             return 0
-        elif square.state == who:
-            to_check = []
-
-            if direction == None:
-                to_check = [((x, y+1), 'r'), ((x-1, y), 'u'), ((x+1, y), 'd'), ((x, y-1), 'l')]
-            if direction == 'r':
-                to_check = [((x, y+1), 'r'),  ((x-1, y), 'u'), ((x+1, y), 'd')]
-            if direction == 'l':
-                to_check = [((x, y-1), 'l'), ((x-1, y), 'u'), ((x+1, y), 'd')]
-            if direction == 'u':
-                to_check = [((x, y+1), 'r'),  ((x-1, y), 'u'), ((x, y-1), 'l')]
-            if direction == 'd':
-                to_check = [((x, y+1), 'r'), ((x, y-1), 'l'),  ((x+1, y), 'd')]
-
+        else:
             liberties = 0
-            for d, c in to_check:
-                liberties += self._has_liberties(d, who, c)
+            for d in [(x, y+1), (x-1, y), (x+1, y), (x, y-1)]:
+                liberties += self._has_liberties(d, who)
 
             return liberties
 
@@ -262,6 +260,12 @@ class Goban:
         return num_deleted
 
 
+    def _clear_checks(self):
+        for row in self.board:
+            for col in row:
+                col.checked = False
+
+
     def draw_board(self, size, img_res):
         ret = pygame.Surface((size,size))