public TermNode ToGoalList(int stackTop, int level) // called during execution (when there is a stack)
{
TermNode result = null;
Term t0, t1;
FType ft = this.FType;
OType ot = this.OType;
int pr = this.Precedence;
if (this is Cut)
{
if (stackTop == 0)
return new TermNode(this, level);
else
return new TermNode(new Cut(stackTop), level);
}
switch (this.Functor)
{
case Parser.IMPLIES:
t0 = Arg(0);
if (!t0.IsGoal)
PrologIO.Error("Illegal predicate head: {0}", t0);
t1 = Arg(1);
result = new TermNode(t0, t1.ToGoalList(stackTop, level));
break;
case Parser.DCGIMPL:
t0 = Arg(0);
if (!t0.IsGoal) PrologIO.Error("Illegal DCG head: {0}", t0);
t1 = Arg(1);
result = new TermNode(t0, t1.ToGoalList(stackTop, level));
break;
case Parser.COMMA:
t0 = Arg(0);
t1 = Arg(1);
result = t0.ToGoalList(stackTop, level);
result.Append(t1.ToGoalList(stackTop, level));
break;
case Parser.DOT:
t0 = Arg(0);
t1 = Arg(1);
if (readingDCGClause)
result = (new ListTerm(t0, t1)).ToGoalList(stackTop, level);
else
result = (new Term("consult", new ListTerm(t0, t1), OType.fy, 0)).ToGoalList(stackTop, level);
break;
case Parser.CURL:
if (readingDCGClause)
{
t0 = Arg(0);
result = t0.ToGoalList(stackTop, level);
}
else
PrologIO.Error("Curly brackets only allowed in a DCG-clause: {0}", this);
break;
default:
if (this.IsVar)
result = new TermNode(new Term("'$metacall'", this), level);
else if (this.IsGoal)
result = new TermNode(this, level);
else
PrologIO.Error("Illegal term {0} in goal list", this);
break;
}
return result;
}
private static void DCGGoal(Term t, ref TermNode body, ref Term remainder, ref bool embedded)
{
Term temp;
if (t.IsString || t is Cut)
body.Append(t);
else if (t.Functor == Parser.CURL)
{
while (t.Arity == 2)
{
body.Append(t.Arg(0));
t = t.Arg(1);
embedded = true;
}
}
else if (t.IsList)
{
temp = new Term();
if (t == NULLLIST) t = temp; else t.SetRightmostArg(temp);
if (embedded)
{
body.Append(new Term(Parser.EQ, remainder, t, FType.comp, OType.xfx, 700));
embedded = false;
}
else
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.IsVar)
PrologIO.Error("Variable not allowed in DCG-clause: {0}", t.VarName());
else
PrologIO.Error("Illegal term in DCG-clause: {0}", t);
}