C++ typedef function definition as a class member to use later for function pointer? -

i need have class stores function definition/prototype class member in order use later function pointers based on definition.

#include <cstdlib> #include <cstdio> #include <functional>  template<typename... ts> class function;  template <typename r> class function<r> { public:     using functype = r (*) ();      function()     {         printf("r()\n");     } };  template <typename r, typename... a> class function<r, a...> { public:     using functype = r (*) (a...);      function()     {         printf("r(a)\n");     } };  void fn1(int i) { printf("called fn1: %d\n", i); } void fn2(int i, float f) { printf("called fn2: %d, %f\n", i, f); } void fn3() { printf("called fn3: n/a \n"); }  int main(int argc, char **argv) {     function<void, int> myfuncx;     function<void, int, float> myfuncy;     function<void> myfuncz;      myfuncx.functype mf1 = fn1;     myfuncy.functype mf2 = fn2;     myfuncz.functype mf3 = fn3;      fn1(244);     fn2(568, 1.891);     fn3();      return exit_success; } 

objects unknown until runtime reason need them class members. they're stored in std::map , need able specific item map , use it's function definition/prototype store pointer of function.

but kind of error:

||=== build: win32 release in sandbox (compiler: gnu gcc compiler) === .\src\testdummy.cpp||in function 'int main(int, char**)': .\src\testdummy.cpp|42|error: invalid use of 'using functype = void (*)(int)' .\src\testdummy.cpp|42|error: expected ';' before 'mf1' .\src\testdummy.cpp|43|error: invalid use of 'using functype = void (*)(int, float)' .\src\testdummy.cpp|43|error: expected ';' before 'mf2' .\src\testdummy.cpp|44|error: invalid use of 'using functype = void (*)()' .\src\testdummy.cpp|44|error: expected ';' before 'mf3' ||=== build failed: 6 error(s), 0 warning(s) (0 minute(s), 0 second(s)) === 

i've tried std::function, typedef etc. why this?

this wrong:

myfuncx.functype mf1 = fn1; 

you can't use type alias normal member - it's declaration inside class' scope, similar typedefs. work:

decltype(myfuncx)::functype mf1 = fn1;