#include <functional>

template <typename T>
struct function_remove_const;

template <typename R, typename... Args>
struct function_remove_const<R(Args...)>
{
    using type = R(Args...);
};

template <typename R, typename... Args>
struct function_remove_const<R(Args...)const>
{
    using type = R(Args...);
};
   
int main()
{
    std::function<function_remove_const<double(float)const>::type> f;
}