public object visitNotSentence(NotSentence notSentence, object arg) { // CNF requires NOT (~) to appear only in literals, so we 'move ~ // inwards' by repeated application of the following equivalences: Sentence negated = notSentence.getNegated(); // ~(~alpha) equivalent to alpha (double negation elimination) if (negated is NotSentence) { return(((NotSentence)negated).getNegated().accept(this, arg)); } if (negated is ConnectedSentence) { ConnectedSentence negConnected = (ConnectedSentence)negated; Sentence alpha = negConnected.getFirst(); Sentence beta = negConnected.getSecond(); // ~(alpha ^ beta) equivalent to (~alpha V ~beta) (De Morgan) if (Connectors.isAND(negConnected.getConnector())) { // I need to ensure the ~s are moved in deeper Sentence notAlpha = (Sentence)(new NotSentence(alpha)).accept(this, arg); Sentence notBeta = (Sentence)(new NotSentence(beta)).accept(this, arg); return(new ConnectedSentence(Connectors.OR, notAlpha, notBeta)); } // ~(alpha V beta) equivalent to (~alpha ^ ~beta) (De Morgan) if (Connectors.isOR(negConnected.getConnector())) { // I need to ensure the ~s are moved in deeper Sentence notAlpha = (Sentence)(new NotSentence(alpha)).accept(this, arg); Sentence notBeta = (Sentence)(new NotSentence(beta)).accept(this, arg); return(new ConnectedSentence(Connectors.AND, notAlpha, notBeta)); } } // in addition, rules for negated quantifiers: if (negated is QuantifiedSentence) { QuantifiedSentence negQuantified = (QuantifiedSentence)negated; // I need to ensure the ~ is moved in deeper Sentence notP = (Sentence)(new NotSentence(negQuantified.getQuantified())).accept(this, arg); // ~FORALL x p becomes EXISTS x ~p if (Quantifiers.isFORALL(negQuantified.getQuantifier())) { return(new QuantifiedSentence(Quantifiers.EXISTS, negQuantified.getVariables(), notP)); } // ~EXISTS x p becomes FORALL x ~p if (Quantifiers.isEXISTS(negQuantified.getQuantifier())) { return(new QuantifiedSentence(Quantifiers.FORALL, negQuantified.getVariables(), notP)); } } return(new NotSentence((Sentence)negated.accept(this, arg))); }
public void testNotSentence() { NotSentence ns = (NotSentence)parser .parse("NOT BrotherOf(John) = EnemyOf(Saladin)"); Assert.AreEqual(ns.getNegated().ToString(), (new TermEquality( getBrotherOfFunction(new Constant("John")), getEnemyOfFunction())).ToString()); }
public Object visitNotSentence(NotSentence sentence, Object arg) { ArgData ad = (ArgData)arg; // Indicate that the enclosed predicate is negated ad.negated = true; sentence.getNegated().accept(this, arg); ad.negated = false; return(sentence); }
public object visitNotSentence(NotSentence sentence, object arg) { sentence.getNegated().accept(this, arg); return(sentence); }
public Object visitNotSentence(NotSentence sentence, Object arg) { return(new NotSentence((Sentence)sentence.getNegated().accept(this, arg))); }
public Object visitNotSentence(NotSentence notSentence, Object arg) { Sentence negated = notSentence.getNegated(); return(new NotSentence((Sentence)negated.accept(this, arg))); }