Question

I’m trying to figure out how to write this function:

template <typename Bound> Bound::result_type callFromAnyList(Bound b, list<any> p) { } 

Then, if I had some function:

double myFunc(string s, int i) {     return -3.0; } 

I could call it by doing something like this:

list<any> p; p.push_back((string)'Hello'); p.push_back(7); double result = callFromAnyList(bind(myFunc, _1, _2), p); 

Is it possible to write something like my callFromAnyList function? Can you inspect the result type and the parameter types from the type returned from bind? And then call any_cast<P1>(*p.begin()), etc? I’ve tried to understand the bind code, but it’s a little hard to follow, and it doesn’t appear as though they wrote it with inspection in mind.

Answer 1

As you updated your concerns in the comment sections, here the answer. Just getting the return type of a function is possible:

template<typename> struct return_of;  template<typename R> struct return_of<R(*)()> {     typedef R type; };  template<typename R, typename P1> struct return_of<R(*)(P1)> {     typedef R type;     typedef P1 parameter_1; };  void foo(int);  template<typename Func> typename return_of<Func>::parameter_1 bar(Func f) {     return 42; }  // call: bar(foo); 

I guess you see what this comes down to 🙂 You can use boost function types which already has solved it: http://www.boost.org/doc/libs/1_37_0/libs/function_types/doc/html/index.html