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"
#include "functionptrt.hpp"
template<typename RT, typename P1 = void,
typename P2 = void,
typename P3 = void>
class FunctionPtr {
private:
typedef typename FunctionPtrT<RT,P1,P2,P3>::Type FuncPtr;
// the encapsulated pointer:
FuncPtr fptr;
public:
// to fit in our framework:
enum { NumParams = FunctionPtrT<RT,P1,P2,P3>::NumParams };
typedef RT ReturnT;
typedef P1 Param1T;
typedef P2 Param2T;
typedef P3 Param3T;
// constructor:
FunctionPtr(FuncPtr ptr)
: fptr(ptr) {
}
// ``function calls'':
RT operator()() {
return fptr();
}
RT operator()(typename ForwardParamT<P1>::Type a1) {
return fptr(a1);
}
RT operator()(typename ForwardParamT<P1>::Type a1,
typename ForwardParamT<P2>::Type a2) {
return fptr(a1, a2);
}
RT operator()(typename ForwardParamT<P1>::Type a1,
typename ForwardParamT<P2>::Type a2,
typename ForwardParamT<P3>::Type a3) {
return fptr(a1, a2, a3);
}
};