public IEnumerable <bool> retract(object Head, object Body)
{
Head = YP.getValue(Head);
if (Head is Variable)
{
throw new PrologException("instantiation_error", "Head is an unbound variable");
}
object[] arguments = YP.getFunctorArgs(Head);
// We always match Head from _allAnswers, and the Body is Atom.a("true").
#pragma warning disable 0168, 0219
foreach (bool l1 in YP.unify(Body, Atom.a("true")))
{
// The caller can assert another answer into this same predicate during yield, so we have to
// make a copy of the answers.
foreach (object[] answer in _allAnswers.ToArray())
{
foreach (bool l2 in YP.unifyArrays(arguments, answer))
{
_allAnswers.Remove(answer);
clearIndexes();
yield return(false);
}
}
}
#pragma warning restore 0168, 0219
}
public IEnumerable <bool> clause(object Head, object Body)
{
Head = YP.getValue(Head);
if (Head is Variable)
{
throw new PrologException("instantiation_error", "Head is an unbound variable");
}
object[] arguments = YP.getFunctorArgs(Head);
// We always match Head from _allAnswers, and the Body is Atom.TRUE.
foreach (bool l1 in YP.unify(Body, Atom.TRUE))
{
// The caller can assert another answer into this same predicate during yield, so we have to
// make a copy of the answers.
foreach (object[] answer in _allAnswers.ToArray())
{
foreach (bool l2 in YP.unifyArrays(arguments, answer))
{
yield return(false);
}
}
}
}
