private static void VisitLiteral(Expression literal, GdlVisitor visitor)
{
visitor.VisitLiteral(literal);
var fact = literal as Fact;
if (fact != null)
{
if (fact.RelationName == GameContainer.Parser.TokDistinct)
VisitDistinct(fact, visitor);
else
VisitSentence(fact, visitor);
}
else if (literal is Negation)
VisitNot((Negation) literal, visitor);
else if (literal is Disjunction)
VisitOr((Disjunction) literal, visitor);
else
throw new Exception("Unexpected GdlLiteral type " + literal.GetType());
}
/// <summary>
/// Unification will try to find a mapping that will go from the second expression to the first.
/// </summary>
/// <param name="exp1">Expression to map to</param>
/// <param name="exp2">Expression to map from</param>
/// <returns>List of mappigs that satify. If none exist returns null</returns>
public static Substitution Mgu(Expression exp1, Expression exp2)
{
if (exp1.GetType() != exp2.GetType())
return null;
var fact1 = exp1 as Fact;
if (fact1 != null)
return Mgu(fact1, (Fact) exp2);
var dis1 = exp1 as Disjunction;
if (dis1 != null)
return Mgu(dis1, (Disjunction) exp2);
var neg1 = exp1 as Negation;
if (neg1 != null)
return Mgu(neg1, (Negation)exp2);
throw new Exception("Unhandled type in unifier Mgu");
}
private static bool Mgu(Expression exp1, Expression exp2, Substitution subsSoFar)
{
if (exp1.GetType() != exp2.GetType())
return false;
var fact1 = exp1 as Fact;
if (fact1 != null)
return Mgu(fact1, (Fact)exp2, subsSoFar);
var dis1 = exp1 as Disjunction;
if (dis1 != null)
return Mgu(dis1, (Disjunction)exp2, subsSoFar);
var neg1 = exp1 as Negation;
if (neg1 != null)
return Mgu(neg1, (Negation)exp2, subsSoFar);
throw new Exception("Unhandled type in unifier Mgu");
}
private static Expression ReplaceRelationInLiteral(Expression literal, ISentenceForm trueForm)
{
var sentence = literal as Fact;
if (sentence != null)
if (trueForm.Matches(sentence))
{
var terms = sentence.GetTerms();
var function = terms[0] as TermFunction;
Debug.Assert(function != null);
return new VariableFact(true, function.FunctionName, function.Arguments);
}
else
return literal;
var not = literal as Negation;
if (not != null)
return new Negation(ReplaceRelationInLiteral(not.Negated, trueForm));
var or = literal as Disjunction;
if (or != null)
{
var newOrBody = new List<Expression>();
for (int i = 0; i < or.GetDisjuncts().Count(); i++)
newOrBody.Add(ReplaceRelationInLiteral(or.Constituents[i], trueForm));
return new Disjunction(newOrBody.ToArray());
}
throw new Exception(string.Format("Unanticipated GDL literal type {0} encountered in Relationizer", literal.GetType()));
}
