// DCG stuff
public TermNode ToDCG(ref BaseTerm lhs) // called from parser
{
TermNode body = new TermNode();
BaseTerm result = null;
BaseTerm inVar = new Variable();
BaseTerm inVarSave = inVar;
BaseTerm outVar = inVar;
lhs = new DcgTerm(lhs, ref outVar); // outVar becomes new term
BaseTerm remainder;
List <BaseTerm> alternatives = AlternativesToArrayList();
for (int i = 0; i < alternatives.Count; i++)
{
BaseTerm alt = alternatives[i];
bool embedded = (alternatives.Count > 1);
List <BaseTerm> terms = alt.ToTermList();
body.Clear();
remainder = inVarSave;
for (int ii = 0; ii < terms.Count; ii++)
{
DCGGoal(terms[ii], ref body, ref remainder, ref embedded);
}
// create a term-tree from the array
if (i == 0)
{
result = body.TermSeq();
}
else
{
result = new OperatorTerm(SemiOpDescr, result, body.TermSeq());
}
((Variable)remainder).Bind(outVar);
}
return((result == null) ? null : result.ToGoalList()); // empty body treated similar to null
}
