public bool RetractAll(BaseTerm t, VarStack varStack)
{
// remark: first-argument indexing is not affected by deleting clauses
string key = t.Key;
if (predefineds.Contains(key))
{
IO.Error("retract of predefined predicate {0} not allowed", key);
}
PredicateDescr pd = this[key];
if (pd == null)
{
return(true);
}
ClauseNode c = pd.ClauseList;
ClauseNode prevc = null;
bool match = false;
while (c != null)
{
BaseTerm cleanTerm = c.Term.Copy();
if (cleanTerm.IsUnifiableWith(t, varStack)) // match found -- remove this head from the chain
{
match = true; // to indicate that at least one head was found
if (prevc == null) // remove first clause
{
if (c.NextClause == null) // we are about to remove the last remaining clause for this predicate
{
predTable.Remove(key); // ... so remove its PredicateDescr as well
break;
}
else
{
pd.SetClauseListHead(c.NextClause);
}
}
else // not the first
{
prevc.NextClause = c.NextClause;
prevc = c;
}
}
else
{
prevc = c;
}
c = c.NextClause;
}
if (match)
{
#if arg1index
pd.DestroyFirstArgIndex(); // rebuilt by ResolveIndices()
#endif
pd.AdjustClauseListEnd();
ResolveIndices();
}
return(true);
}
public bool Retract(BaseTerm t, VarStack varStack, BaseTerm where)
{
string key = t.Key;
if (predefineds.Contains(key))
{
IO.Error("retract of predefined predicate {0} not allowed", key);
}
PredicateDescr pd = this[key];
if (pd == null)
{
return(false);
}
InvalidateCrossRef();
ClauseNode c = pd.ClauseList;
ClauseNode prevc = null;
BaseTerm cleanTerm;
int top;
while (c != null)
{
cleanTerm = c.Head.Copy();
top = varStack.Count;
if (cleanTerm.Unify(t, varStack)) // match found -- remove this term from the chain
{
if (prevc == null) // remove first clause
{
if (c.NextClause == null) // we are about to remove the last remaining clause for this predicate
{
predTable.Remove(key); // ... so remove its PredicateDescr as well
#if arg1index
pd.CreateFirstArgIndex(); // re-create
#endif
ResolveIndices();
}
else
{
pd.SetClauseListHead(c.NextClause);
}
}
else // not the first
{
prevc.NextClause = c.NextClause;
prevc = c;
pd.AdjustClauseListEnd();
#if arg1index
pd.CreateFirstArgIndex(); // re-create
#endif
}
return(true); // possible bindings must stay intact (e.g. if p(a) then retract(p(X)) yields X=a)
}
Variable s;
for (int i = varStack.Count - top; i > 0; i--) // unbind all vars that got bound by the above Unification
{
s = (Variable)varStack.Pop();
s.Unbind();
}
prevc = c;
c = c.NextClause;
}
ResolveIndices();
return(false);
}