C function pointers with C++11 lambdas

Question

So i\'m trying to write an Integration function to be used with c++11 lambdas. The code looks something like this:

double Integrate(std::function

        

Answer 1

Looks like the gsl library requires a function pointer. A lambda which does not capture can be converted to a function pointer. Any lambda can be converted to a std::function. But a std::function cannot be converted to a function pointer.

You could try:

struct functor_and_params {
  std::function f;
  void* params;
  static double invoke(double x, void* ptr) {
      functor_and_params& f_and_p = *reinterpret_cast(ptr);
      return f_and_p.f(x, f_and_p.params);
  }
};

double Integrate(std::function func,
                 double a,double b,std::vector & params) {
    functor_and_params f_and_p{ func, ¶ms };
    gsl_function F;
    F.function = &functor_and_params::invoke;
    F.params = &f_and_p;
    //...
 }