public bool UnifiesNoUndo(ITerm term, ITerm term2)
{
if (term == null && term2 == null)
{
return(true);
}
if (term == null && term2 != null)
{
return(false);
}
if (term != null && term2 == null)
{
return(false);
}
Pred np1 = null;
Pred np2 = null;
if (np1.GetType() == typeof(Pred) && np2.GetType() == typeof(Pred))
{
np1 = (Pred)term;
np2 = (Pred)term2;
// tests when np1 or np2 are variables with annotations
if (np1.IsVar() && np1.HasAnnot() || np2.IsVar() && np2.HasAnnot())
{
if (!np1.HasSubsetAnnot(np2, this))
{
return(false);
}
}
}
if (term.IsCyclicTerm() && term2.IsCyclicTerm()) // Both are cycled terms
{
// Unification of cyclic terms: Remove variables to avoid loops and test the structure, then reintroduce vars
VarTerm v1 = term.GetCyclicVar();
VarTerm v2 = term2.GetCyclicVar();
Remove(v1);
Remove(v2);
try
{
return(UnifiesNoUndo(new LiteralImpl((Literal)term), new LiteralImpl((Literal)term2)));
}
finally
{
function.Add(v1, term);
function.Add(v2, term2);
}
}
else
{
if (term.IsCyclicTerm() && Get(term.GetCyclicVar()) == null) // Reintroduce cycles in the unifier
{
function.Add(term.GetCyclicVar(), term);
}
if (term2.IsCyclicTerm() && Get(term.GetCyclicVar()) == null)
{
function.Add(term2.GetCyclicVar(), term2);
}
}
// Unify as Term
bool ok = UnifyTerms(term, term2);
// If term is a unified variable, clear its annotations
if (ok && term != null) // Both are predicates
{
if (term.IsVar() && ((Pred)term).HasAnnot())
{
term = Deref((VarTerm)term); // ???
ITerm termvl;
function.TryGetValue((VarTerm)term, out termvl);
if (termvl != null && termvl.IsPred())
{
Pred pvl = (Pred)termvl.Clone();
pvl.ClearAnnots();
Bind((VarTerm)term, pvl);
}
}
if (term2.IsVar() && ((Pred)term2).HasAnnot())
{
term2 = Deref((VarTerm)term2);
ITerm term2vl;
function.TryGetValue((VarTerm)term2, out term2vl);
if (term2vl != null && term2vl.IsPred())
{
Pred pvl = (Pred)term2vl.Clone();
pvl.ClearAnnots();
Bind((VarTerm)term2, pvl);
}
}
}
return(ok);
}
