/* The following code example is taken from the book * "C++ Templates - The Complete Guide" * by David Vandevoorde and Nicolai M. Josuttis, Addison-Wesley, 2002 * * (C) Copyright David Vandevoorde and Nicolai M. Josuttis 2002. * Permission to copy, use, modify, sell and distribute this software * is granted provided this copyright notice appears in all copies. * This software is provided "as is" without express or implied * warranty, and with no claim as to its suitability for any purpose. */#include <cmath>#include <cstdlib>class Abs {  public:    // ``function call'':    double operator() (double v) const {         return std::abs(v);     }};class Sine {  public:    // ``function call'':    double operator() (double a) const {        return std::sin(a);     }};