public void Assert(BaseTerm assertion, bool asserta)
{
BaseTerm head;
TermNode body = null;
PredicateDescr pd;
if (assertion.HasFunctor(PrologParser.IMPLIES))
{
head = assertion.Arg(0);
body = assertion.Arg(1).ToGoalList();
}
else
{
head = assertion;
}
if (!head.IsCallable)
{
IO.Error("Illegal predicate head '{0}'", head.ToString());
}
string key = head.Key;
if ((predefineds.Contains(key)) || (head.Precedence >= 1000))
{
IO.Error("assert/1 cannot be applied to predefined predicate or operator '{0}'",
assertion.Index);
}
predTable.TryGetValue(key, out pd);
ClauseNode newC = new ClauseNode(head, body);
if (pd == null) // first head
{
SetClauseList(head.FunctorToString, head.Arity, newC);
ResolveIndices();
}
else if (pd.IsCacheable)
{
IO.Error("assert/1 cannot be applied to cached predicate '{0}'",
assertion.Index);
}
else if (asserta) // at beginning
{
newC.NextClause = pd.ClauseList; // pd.ClauseList may be null
SetClauseList(head.FunctorToString, head.Arity, newC);
#if arg1index
pd.CreateFirstArgIndex(); // re-create
#endif
}
else // at end
{
pd.AppendToClauseList(newC);
#if arg1index
pd.CreateFirstArgIndex(); // re-create
#endif
}
InvalidateCrossRef();
}