private Fact RenameDistinct(Fact distinct, Dictionary<TermVariable, TermVariable> renamings)
{
if (distinct is GroundFact)
return distinct;
Term arg1 = RenameTerm(distinct.GetTerm(0), renamings);
Term arg2 = RenameTerm(distinct.GetTerm(1), renamings);
return new VariableFact(false, distinct.RelationName, arg1, arg2);
}
private static Fact SubstituteDistinct(Fact distinct, Substitution theta)
{
if (distinct is GroundFact)
return distinct;
Term arg1 = SubstituteTerm(distinct.GetTerm(0), theta);
Term arg2 = SubstituteTerm(distinct.GetTerm(1), theta);
return arg1.HasVariables || arg2.HasVariables
? new VariableFact(false, distinct.RelationName, arg1, arg2)
: (Fact) new GroundFact(distinct.RelationName, arg1, arg2);
}
private static void VisitDistinct(Fact distinct, GdlVisitor visitor)
{
visitor.VisitDistinct(distinct);
VisitTerm(distinct.GetTerm(0), visitor);
VisitTerm(distinct.GetTerm(1), visitor);
}
private static bool Mgu(Fact f1, Fact f2, Substitution subsSoFar)
{
// Make sure this is even worth our time to check
if (f1.RelationName != f2.RelationName)
return false;
if (f1.Arity != f2.Arity)
return false;
// Find the mgu for each column of the facts
for (int i = 0; i < f1.Arity; i++)
{
// If there is no mgu, just die
if (Mgu(f1.GetTerm(i), f2.GetTerm(i), subsSoFar) == false)
return false;
}
return true;
}
/// <summary>
/// Returns true iff the given sentence is of this sentence form.
/// </summary>
public override bool Matches(Fact sentence)
{
if (sentence.RelationName != Name || sentence.Arity != _arity)
return false;
for (int i = 0; i < sentence.Arity; i++)
{
var term = sentence.GetTerm(i) as TermFunction;
if (term == null && _functions.ContainsKey(i))
return false;
if (term != null)
{
if (!_functions.ContainsKey(i) || !_functions[i].Matches(term))
return false;
}
}
return true;
}
private static Fact SubstituteSentence(Fact sentence, Substitution theta)
{
if (sentence is GroundFact)
return sentence;
var body = new List<Term>();
for (int i = 0; i < sentence.Arity; i++)
body.Add(SubstituteTerm(sentence.GetTerm(i), theta));
var variableFact = new VariableFact(false, sentence.RelationName, body.ToArray());
return variableFact.VariablesOrEmpty.Any()
? variableFact
: (Fact) new GroundFact(sentence.RelationName, body.ToArray());
}
private Fact RenameSentence(Fact sentence, Dictionary<TermVariable, TermVariable> renamings)
{
if (sentence is GroundFact)
return sentence;
var body = new List<Term>();
for (int i = 0; i < sentence.Arity; i++)
body.Add(RenameTerm(sentence.GetTerm(i), renamings));
return new VariableFact(false, sentence.RelationName, body.ToArray());
}
private void AskDistinct(Fact distinct, LinkedList<Expression> goals, KnowledgeBase context, Substitution theta,
ProverCache cache, VariableRenamer renamer, bool askOne, HashSet<Substitution> results, HashSet<Fact> alreadyAsking)
{
if (!distinct.GetTerm(0).Equals(distinct.GetTerm(1)))
Ask(goals, context, theta, cache, renamer, askOne, results, alreadyAsking);
}