// insert tuples, discard duplicates
public void Insert(RelValueST <T> value)
{
Value = Rel.Create(RelOpsST.Union(Value, value));
}
// generate a new relation that is a set union
public RelValueST <Ttup> Union(RelValueST <Ttup> other)
{
var newbody = RelOpsST.Union <Ttup>(this, other);
return(Create <RelValueST <Ttup> >(newbody));
}