added example 7.2_15

% nacteni:

/* ['7.2_15.pl']. */

alphabeta(Pos, Alpha, Beta, GoodPos, Val) :- moves( Pos, PosList), !,

    boundedbest( PosList, Alpha, Beta, GoodPos, Val);

    staticval(Pos, Val ). % Static value of Pos

boundedbest([Pos | PosList], Alpha, Beta, GoodPos, GoodVal) :-

    alphabeta(Pos, Alpha, Beta,_ , Val ),

    goodenough(PosList, Alpha, Beta, Pos, Val, GoodPos, GoodVal).

goodenough([],_,_, Pos, Val, Pos, Val) :- ! . % No other candidate

goodenough(_, Alpha, Beta, Pos, Val, Pos, Val) :-

    min_to_move(Pos), Val > Beta, ! % Maximizer attained upper bound

    ; 

    max_to_move(Pos), Val < Alpha, !. % Minimizer attained lower bound

goodenough(PosList, Alpha, Beta, Pos, Val, GoodPos, GoodVal) :-

    newbounds(Alpha, Beta, Pos, Val, NewAlpha, NewBeta), % Refine bounds

    boundedbest(PosList, NewAlpha, NewBeta, Pos1, Val1),

    betterof(Pos, Val, Pos1, Val1, GoodPos, GoodVal).

newbounds( Alpha, Beta, Pos, Val, Val, Beta) :-

    min_to_move( Pos), Val > Alpha, !. % Maximizer increased lower bound

newbounds( Alpha, Beta, Pos, Val, Alpha, Val) :-

    max_to_move( Pos), Val < Beta, !. % Minimizer decreased upper bound

newbounds( Alpha, Beta, _, _, Alpha, Beta). % Otherwise bounds unchanged

betterof(Pos, Val, _Pos1, Val1, Pos, Val) :- min_to_move( Pos), Val > Val1, !

    ; max_to_move( Pos), Val < Val1, !. % Pos better than Pos1

betterof(_,_, Pos1, Val1, Pos1, Val1). % Otherwise Pos1 better

#!/usr/bin/env python

# encoding=utf-8 (pep 0263)

from linked_lists import LinkedList, Nil

def alphabeta(pos, alpha, beta):

    poslist = moves(pos)

    if poslist == Nil:

        return (None, staticval(pos))

    return bounded_best(poslist, alpha, beta)

def bounded_best(poslist, alpha, beta):

    pos = poslist.head

    _, val = alphabeta(pos, alpha, beta)

    return good_enough(poslist.tail, alpha, beta, pos, val)

def good_enough(poslist, alpha, beta, pos, val):

    if poslist == Nil or (min_to_move(pos) and val > beta or \

       max_to_move(pos) and val < alpha):

        return (pos, val)

    new_alpha, new_beta = new_bounds(alpha, beta, pos, val)

    pos1, val1 = bounded_best(poslist, new_alpha, new_beta)

    return better_of(pos, val, pos1, val1)

def new_bounds(alpha, beta, pos, val):

    if min_to_move(pos) and val > alpha:

        return (val, beta)

    if max_to_move(pos) and val < beta:

        return (alpha, val)

    return (alpha, beta)

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 s alfa-beta prořezáváním - 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 alphabeta('root', 0, 9999): %s" % (alphabeta("root", 0, 9999),))

Minimax s alfa-beta prořezáváním - 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 alphabeta('root', 0, 9999): ('a1', 3)