Variadic function to call lambda and pass parameters separately

Question

I want to call a lambda and pass the parameters separately.

eg:

#include <memory>

template<typename T, typename... TS>
T call(T (*)(TS...) f, TS&&... args) {
    return f(std::forward<TS...>(args...));
}

Thus I want to call this function like this:

call([](auto arg1, auto arg2){
    std::cout << arg1 << ", " << arg2 << std::endl;
}, 1, 2);

This should print out 1, 2 .

Answer 1

You can't just slap ... everywhere and hope it works. Understand how parameter packs work and use the correct syntax. Furthermore, the function call() should not return T . Use auto for the return type. And T is already the full type of f , you should not write T (*)(TS...) . Here is the fixed version:

template<typename T, typename... TS>
auto call(T f, TS&&... args) {
    return f(std::forward<TS>(args)...);
}