added example 8.2_20

% nacteni:

/* ['8.2_20.pl']. */

% pomocne funkce - jen "zaslepky"

% symboly P1, P2, P3

proposition_symbols([p1,p2,p3],_).

% priklad: KB = P2 and P3

%          alpha = P2

%          beta = P1

pl_true(kb,   [p3-true, p2-true, p1-true]):-!.

pl_true(kb,   [p3-true, p2-true, p1-false]):-!.

pl_true(alpha,[p3-true, p2-true, p1-true]):-!.

pl_true(alpha,[p3-false,p2-true, p1-true]):-!.

pl_true(alpha,[p3-true, p2-true, p1-false]):-!.

pl_true(alpha,[p3-false,p2-true, p1-false]):-!.

pl_true(beta, [p3-true, p2-true, p1-true]):-!.

pl_true(beta, [p3-true, p2-false,p1-true]):-!.

pl_true(beta, [p3-false,p2-true, p1-true]):-!.

pl_true(beta, [p3-false,p2-false,p1-true]):-!.

% tt_entails(+KB,+Alpha)

tt_entails(KB,Alpha):-proposition_symbols(Symbols,[KB,Alpha]),

    tt_check_all(KB,Alpha,Symbols,[]).

% tt_check_all(+KB,+Alpha,+Symbols,+Model)

tt_check_all(KB,Alpha,[],Model):-pl_true(KB,Model),!,pl_true(Alpha,Model).

tt_check_all(_KB,_Alpha,[],_Model):-!.

tt_check_all(KB,Alpha,[P|Symbols],Model):-

    tt_check_all(KB,Alpha,Symbols,[P-true|Model]),

    tt_check_all(KB,Alpha,Symbols,[P-false|Model]).

show_bool(Text,P):-write(Text),call(P),!,write('yes'),nl.

show_bool(_,_):-write('no'),nl.

%:- trace,tt_entails(kb,alpha).

:- show_bool('KB entails Alpha: ', tt_entails(kb,alpha)), % true

   show_bool('KB entails Beta: ', tt_entails(kb,beta)).  % false

#!/usr/bin/env python

# encoding=utf-8 (pep 0263)

from linked_lists import LinkedList, Cons, Nil

def preposition_symbols(_):

    # zavisi na resenem problemu

    return LinkedList(["p1", "p2", "p3"])

def pl_true(formula, model):

    # zavisi na resenem problemu

    if formula == "kb":

        return model == LinkedList([("p3", True), ("p2", True), ("p1", True)]) or \

               model == LinkedList([("p3", True), ("p2", True), ("p1", False)])

    if formula == "alpha":

        return model == LinkedList([("p3", True), ("p2", True), ("p1", True)]) or \

               model == LinkedList([("p3", False), ("p2", True), ("p1", True)]) or \

               model == LinkedList([("p3", True), ("p2", True), ("p1", False)]) or \

               model == LinkedList([("p3", False), ("p2", True), ("p1", False)])

    if formula == "beta":

        return model == LinkedList([("p3", True), ("p2", True), ("p1", True)]) or \

               model == LinkedList([("p3", True), ("p2", False), ("p1", True)]) or \

               model == LinkedList([("p3", False), ("p2", True), ("p1", True)]) or \

               model == LinkedList([("p3", False), ("p2", False), ("p1", True)])

def tt_entails(kb, alpha):

    symbols = preposition_symbols(LinkedList([kb, alpha]))

    return tt_check_all(kb, alpha, symbols, Nil)

def tt_check_all(kb, alpha, symbols, model):

    if symbols == Nil:

        if pl_true(kb, model):

            return pl_true(alpha, model)

        return True

    p = symbols.head

    return tt_check_all(kb, alpha, symbols.tail, Cons((p, True), model)) and \

           tt_check_all(kb, alpha, symbols.tail, Cons((p, False), model))

# demonstracni vypis

if __name__ == "__main__":

    print("KB entails Alpha: %s" % tt_entails("kb", "alpha"))

    print("KB entails Beta: %s" % tt_entails("kb", "beta"))

KB entails Alpha: True

KB entails Beta: False