The following code example is taken from the book
C++ Templates - The Complete Guide
by David Vandevoorde and Nicolai M. Josuttis, Addison-Wesley, 2002
© Copyright David Vandevoorde and Nicolai M. Josuttis 2002
#include "forwardparam.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;
typedef typename FO1::Param1T Param1T;
// constructor: initialize function objects
Composer(FO1 f1, FO2 f2)
: BaseMem<FO1,1>(f1), BaseMem<FO2,2>(f2) {
}
// ``function call'': nested call of function objects
ReturnT operator() (typename ForwardParamT<Param1T>::Type v) {
return BaseMem<FO2,2>::operator()
(BaseMem<FO1,1>::operator()(v));
}
};