added example 8.2_20

8.2_20.pl

+% 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

8.2_20.py

+#!/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"))

8.2_20.py.out

+KB entails Alpha: True
+KB entails Beta: False