C++ How to Program, 10/e

10.6 Overloading Unary Operators

A unary operator for a class can be overloaded as a non-static member function with no arguments or as a non-member function with one argument that must be an object (or a reference to an object) of the class. Member functions that implement overloaded operators must be non-static so that they can access the non-static data in each object of the class.

Unary Overloaded Operators as Member Functions

Consider overloading unary operator ! to test whether an object of your own String class is empty. Such a function would return a bool result. When a unary operator such as ! is overloaded as a member function with no arguments and the compiler sees the expression !s (in which s is an object of class String), the ...