42   return new Not(*
this);
 
Expression * clone() const 
It creates a new copy of this expression. 
 
UnaryOp & operator=(const UnaryOp &rhs)
 
TE_DEFINE_VISITABLE Not(Expression *arg)
Constructor. 
 
Boolean NOT operator - syntatic-suggar. 
 
A base class for unary operators. 
 
This is an abstract class that models a query expression. 
 
Not & operator=(const Not &rhs)