public void Unify(XPredicate src, XPredicate dest, IXExpression expression)
{
for (int i = 0; i < src.Signature.Arity; ++i)
{
var sArg = src.Vars[i];
var dArg = dest.Vars[i];
if (sArg.Type == XType.Var && dArg.Type == XType.Const)
{
expression.Bind(sArg, dArg);
}
}
}
public bool Resolve(XPredicate target, IXExpression expression, out List <XPredicate> facts, out List <XPredicate> localFacts)
{
if (expression == null)
{
facts = new List <XPredicate>();
localFacts = new List <XPredicate>();
return(true);
}
switch (expression.Type)
{
case XOperand.Predicate:
var predicateExp = expression as XExpression;
facts = new List <XPredicate>();
if (Run(predicateExp.Predicate, out localFacts))
{
foreach (var f in localFacts)
{
var clone = target.Clone();
for (int i = 0; i < f.Vars.Length; ++i)
{
var sArg = predicateExp.Predicate.Vars[i];
var dArg = f.Vars[i];
if (sArg.Type == XType.Var && dArg.Type == XType.Const)
{
clone.Bind(sArg, dArg);
}
}
facts.Add(clone);
}
return(true);
}
return(false);
case XOperand.Not:
var notExp = expression as XNot;
return(!Resolve(target, notExp.Expression.Clone(), out facts, out localFacts));
default:
var andExp = expression as XAnd;
return(Resolve2(target, andExp, out facts, out localFacts));
}
}
public XNot(IXExpression expression)
{
Expression = expression;
}
private int ParseExpression(List <XToken <XTokenType> > tokens, int start, int end, XDatabase db, out IXExpression expression)
{
int position = start;
expression = null;
var expressions = new List <IXExpression>();
for (; position < end; ++position)
{
position = ParseExpression2(tokens, position, end, db, out IXExpression child);
expressions.Add(child);
if (tokens[position].Type != XTokenType.Separator)
{
break;
}
}
if (expressions.Count == 0)
{
throw new ApplicationException("Clause has an empty body");
}
else if (expressions.Count == 1)
{
expression = expressions[0];
}
else
{
expression = new XAnd(expressions.ToArray());
}
return(position);
}
private int ParseExpression2(List <XToken <XTokenType> > tokens, int start, int end, XDatabase db, out IXExpression expression)
{
int position = start;
if (tokens[position].Type == XTokenType.Not)
{
position = ParsePredicate(tokens, position + 1, end, db, out XPredicate predicate);
expression = new XNot(new XExpression(predicate));
}
else
{
position = ParsePredicate(tokens, position, end, db, out XPredicate predicate);
expression = new XExpression(predicate);
}
return(position);
}
public XClause(IXExpression body, XSignature signature, params XVar[] vars) : this(body, new XPredicate(signature, vars))
{
}
public XClause(IXExpression body, XPredicate predicate)
{
Body = body;
Predicate = predicate;
}