added example 7.1_11

7.1_11.pl

+% nacteni:
+/* ['7.1_11.pl']. */
+
+% minimax( Pos, BestSucc, Val ):
+% Pos is a position , Val is its minimax value ;
+% best move from Pos leads to position BestSucc
+minimax(Pos, BestSucc, Val) :-
+    moves(Pos, PosList), ! ,   % Legal moves in Pos produce PosList
+    best(PosList, BestSucc, Val)
+    ;
+    staticval( Pos, Val ).     % Pos has no successors : evaluate statically
+    
+best([Pos], Pos, Val) :-
+    minimax(Pos,_, Val), ! .
+best([Pos1 | PosList], BestPos, BestVal) :-
+    minimax(Pos1,_, Val1),
+    best(PosList, Pos2, Val2),
+    betterof(Pos1, Val1, Pos2, Val2, BestPos, BestVal).
+betterof(Pos0, Val0, _Pos1, Val1, Pos0, Val0) :-    % Pos0 better than Pos1
+    min_to_move(Pos0),				    % MIN to move in Pos0
+    Val0 > Val1, !				    % MAX prefers the greater value
+    ;
+    max_to_move(Pos0),                              % MAX to move in Pos0
+    Val0 < Val1, ! .				    % MIN prefers the lesser value
+betterof(_Pos0, _Val0, Pos1, Val1, Pos1, Val1).	    % Otherwise Pos1 better than Pos0

7.1_11.py

+#!/usr/bin/env python
+# encoding=utf-8 (pep 0263)
+
+from linked_lists import LinkedList, Nil
+
+def minimax(pos):
+    poslist = moves(pos)
+    if poslist == Nil:
+        return (None, staticval(pos))
+    return best(poslist)
+
+def best(poslist):
+    pos1 = poslist.head
+    if poslist.tail == Nil:
+        return minimax(pos1)
+    _, val1 = minimax(pos1)
+    pos2, val2 = best(poslist.tail)
+    return better_of(pos1, val1, pos2, val2)
+
+def better_of(pos0, val0, pos1, val1):
+    if min_to_move(pos0) and val0 > val1 or max_to_move(pos0) and val0 < val1:
+        return (pos0, val0)
+    return (pos1, val1)
+
+start = "root"
+graph = dict(
+    root=("max", LinkedList(["a1", "a2", "a3"])),
+    a1=("min", LinkedList(["b1", "b2", "b3"])),
+    a2=("min", LinkedList(["c1", "c2", "c3"])),
+    a3=("min", LinkedList(["d1", "d2", "d3"])),
+    b1=("max", Nil), b2=("max", Nil), b3=("max", Nil),
+    c1=("max", Nil), c2=("max", Nil), c3=("max", Nil),
+    d1=("max", Nil), d2=("max", Nil), d3=("max", Nil))
+
+def moves(pos):
+    # zavisi na resenem problemu
+    return graph[pos][1]
+
+def min_to_move(pos):
+    return graph[pos][0] == "min"
+
+def max_to_move(pos):
+    return graph[pos][0] == "max"
+
+staticvals = dict(
+    b1=3, b2=12, b3=8,
+    c1=2, c2=4, c3=6,
+    d1=14, d2=5, d3=2)
+
+def staticval(pos):
+    # zavisi na resenem problemu
+    if pos not in staticvals:
+        raise ValueError("Uzel %s neni cilovy." % pos)
+    return staticvals[pos]
+
+# demonstracni vypis
+if __name__ == "__main__":
+    print("Minimax - hra na jedno kolo\n")
+
+    print("            root            ")
+    print("      a1     a2     a3      ")
+    print("b1 b2 b3  c1 c2 c3  d1 d2 d3\n")
+
+    print(" 3 12  8   2  4  6  14  5  2\n")
+
+    print("Vysledek volani minimax('root'): %s" % (minimax("root"),))

7.1_11.py.out

+Minimax - hra na jedno kolo
+
+            root            
+      a1     a2     a3      
+b1 b2 b3  c1 c2 c3  d1 d2 d3
+
+ 3 12  8   2  4  6  14  5  2
+
+Vysledek volani minimax('root'): ('a1', 3)