public static Substitution Unify(ISentence sentence1, ISentence sentence2)
{
var res = new Substitution();
res.Successful = false;
switch (sentence1.GetSentenceType())
{
case SentenceType.Predicate:
if (sentence2.GetSentenceType() == SentenceType.QuantifierVariableSentence)
{
var qvs2 = sentence2 as QuantifierVariableSentence;
if (qvs2.Quantifier != Quantifier.Exists)
{
break;
}
return(Unify(sentence1, qvs2.Sentence));
}
if (sentence2.GetSentenceType() == SentenceType.SentenceConnectiveSentence)
{
break;
}
var pred1 = sentence1 as Predicate;
var pred2 = sentence2 as Predicate;
return(PredicateUnify(pred1, pred2));
case SentenceType.SentenceConnectiveSentence:
if (sentence1.GetSentenceType() != sentence2.GetSentenceType())
{
break;
}
var scs1 = sentence1 as SentenceConnectiveSentence;
var scs2 = sentence1 as SentenceConnectiveSentence;
return(Unify(scs1.Sentence1, scs2.Sentence1).Compose(Unify(scs1.Sentence2, scs2.Sentence2)));
case SentenceType.QuantifierVariableSentence:
var qvs1 = sentence1 as QuantifierVariableSentence;
if (qvs1.Quantifier == Quantifier.Exists)
{
return(Unify(qvs1.Sentence, sentence2));
}
break;
default:
return(res);
}
return(res);
}
public static ISentence DropOuterQuantifiers(ISentence sentence)
{
switch (sentence.GetSentenceType())
{
case SentenceType.Predicate:
return(sentence);
case SentenceType.SentenceConnectiveSentence:
return(sentence);
default: //QuantifierVariableSentence
var quantifiedSentence = sentence as QuantifierVariableSentence;
if (quantifiedSentence.Quantifier == Quantifier.All)
{
return(DropOuterQuantifiers(quantifiedSentence.Sentence));
}
else
{
return(sentence);
}
}
}