// remove tuples that satisfy predicate
public void Delete(string heading, Func <Tup, bool> selfunc)
{
var head = CommonHeading.Create(heading);
var map = head.CreateMap(Heading);
Value = new RelValue(Heading, Value.Where(t => !selfunc(RelStatic.CreateByMap <Tup>(t, map))));
}
// update tuples that satisfy predicate
public void Update(string heading, Func <Tup, bool> selfunc, object newvalue)
{
// map for selection tuple
var head1 = CommonHeading.Create(heading);
var map1 = head1.CreateMap(Heading);
// map for replace tuple
var head2 = Heading.Remove(head1.Fields.Last()).Append(CommonField.Empty);
var map2 = head2.CreateMap(Heading);
Value = new RelValue(Heading, Value.Select(t => selfunc(RelStatic.CreateByMap <Tup>(t, map1))
? RelStatic.CreateByMap <Tup>(t, map2, newvalue) : t));
}
public RelVar(RelNode node)
{
Value = new RelValue(node);
}
public void Insert(RelNode node)
{
Value = new RelValue(Heading, Value.Body.Union(node));
}
public RelVar()
{
Value = new RelValue();
}
