static void DCGGoal(BaseTerm t, ref TermNode body, ref BaseTerm remainder, ref bool embedded)
{
BaseTerm temp;
if (t.IsString || t is Cut)
{
body.Append(t);
}
else if (t.HasFunctor(PrologParser.CURL))
{
while (t.Arity == 2)
{
body.Append(t.Arg(0));
t = t.Arg(1);
embedded = true;
}
}
else if (t.IsProperList)
{
temp = new Variable();
t = (t.IsEmptyList) ? temp : ((ListTerm)t).Append(temp);
if (embedded)
{
body.Append(new CompoundTerm(PrologParser.EQ, remainder, t));
embedded = false;
}
else
{
((Variable)remainder).Bind(t);
}
// in this case, nothing is appended to body, which may be left empty (e.g. t-->[x])
remainder = temp;
}
else if (t.IsAtom || t.IsCompound)
{
t = new DcgTerm(t, ref remainder);
body.Append(t);
}
else if (t.IsNamedVar)
{
IO.Error("Variable not allowed in DCG-clause: {0}", ((NamedVariable)t).Name);
}
else if (t.IsUnboundTerm)
{
IO.Error("Unbound variable not allowed in DCG-clause");
}
else
{
IO.Error("Illegal term in DCG-clause: {0}", t);
}
}
public TermNode ToGoalList(int stackSize, int level) // called during execution (when there is a stack)
{
TermNode result = null;
BaseTerm t0, t1;
TermType tt = this.TermType;
AssocType at = this.AssocType;
int pr = this.Precedence;
if (this is Cut)
{
if (stackSize == 0)
{
return(new TermNode(this, null, level));
}
else
{
return(new TermNode(new Cut(stackSize), null, level));
}
}
switch (this.Functor as string)
{
case PrologParser.IMPLIES:
t0 = Arg(0);
if (!t0.IsCallable)
{
IO.Error("Illegal predicate head: {0}", t0);
}
t1 = Arg(1);
result = new TermNode(t0, t1.ToGoalList(stackSize, level));
break;
case PrologParser.DCGIMPL:
t0 = Arg(0);
if (!t0.IsCallable)
{
IO.Error("Illegal DCG head: {0}", t0);
}
t1 = Arg(1);
result = new TermNode(t0, t1.ToGoalList(stackSize, level));
break;
case PrologParser.COMMA:
t0 = Arg(0);
t1 = Arg(1);
result = t0.ToGoalList(stackSize, level);
result.Append(t1.ToGoalList(stackSize, level));
break;
case PrologParser.DOT:
t0 = Arg(0);
t1 = Arg(1);
result = (new CompoundTerm("consult", new ListTerm(t0, t1))).ToGoalList(stackSize, level);
break;
case PrologParser.CURL:
t0 = Arg(0);
result = t0.ToGoalList(stackSize, level);
break;
default:
if (this.IsVar)
{
result = new TermNode(new CompoundTerm("meta$call", this), null, level);
}
else if (this.IsCallable)
{
result = new TermNode(this, null, level);
}
else
{
IO.Error("Illegal term {0} in goal list", this);
}
break;
}
return(result);
}
