/* 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 "forwardparam.hpp"#include "functorparam.hpp"template <typename C, int N> class BaseMem : public C {  public:    BaseMem(C& c) : C(c) { }    BaseMem(C const& c) : C(c) { }};template <typename FO1, typename FO2>class Composer : private BaseMem<FO1,1>,                 private BaseMem<FO2,2> {  public:    // to let it fit in our framework:    enum { NumParams = FO1::NumParams };    typedef typename FO2::ReturnT ReturnT;    // define Param1T, Param2T, and so on    // - use a macro to ease the replication of the parameter type construct#define ComposeParamT(N)                                            \        typedef typename FunctorParam<FO1, N>::Type Param##N##T    ComposeParamT(1);    ComposeParamT(2);    //...#undef ComposeParamT    // constructors: initialize function objects    Composer(FO1 const& f1, FO2 const& f2)     : BaseMem<FO1,1>(f1), BaseMem<FO2,2>(f2) {    }    Composer(FO1 const& f1, FO2& f2)     : BaseMem<FO1,1>(f1), BaseMem<FO2,2>(f2) {    }    Composer(FO1& f1, FO2 const& f2)     : BaseMem<FO1,1>(f1), BaseMem<FO2,2>(f2) {    }    Composer(FO1& f1, FO2& f2)     : BaseMem<FO1,1>(f1), BaseMem<FO2,2>(f2) {    }    // ``function call'' for no argument:    ReturnT operator() () {      return BaseMem<FO2,2>::operator()(BaseMem<FO1,1>::operator()());    }    // ``function call'' for one argument:    ReturnT operator() (typename ForwardParamT<Param1T>::Type v1) {        return BaseMem<FO2,2>::operator()(BaseMem<FO1,1>::operator()(v1));    }    // ``function call'' for two arguments:    ReturnT operator() (typename ForwardParamT<Param1T>::Type v1,                        typename ForwardParamT<Param2T>::Type v2) {        return BaseMem<FO2,2>::operator()(BaseMem<FO1,1>::operator()(v1, v2));    }    //...};