ex2.cpp

/*
    "`for_each_arg` explained and expanded"
    C++Now 2015 Lightning Talk
    - Vittorio Romeo

    http://vittorioromeo.info
    vittorio.romeo@outlook.com
*/

#include <iostream>
#include <vector>

template <typename TF, typename... Ts>
void forArgs(TF&& mFn, Ts&&... mArgs)
{
    return (void)std::initializer_list<int>{
        (mFn(std::forward<Ts>(mArgs)), 0)...};
}

// Example use case: `make_vector` function.

// `make_vector` will take one or more arguments of the same type
// and return an `std::vector` containing them.

// We'll pass the first parameter outside of the variadic pack
// to help us deduce the type of the arguments.

template <typename T, typename... TArgs>
auto make_vector(T&& mArg, TArgs&&... mArgs)
{
    std::vector<T> result;
    result.reserve(1 + sizeof...(TArgs));

    forArgs(
        [&result](auto&& x)
        {
            result.emplace_back(std::forward<decltype(x)>(x));
        },

        std::forward<T>(mArg), std::forward<TArgs>(mArgs)...);

    return result;
}

int main()
{
    // Prints "12345".

    auto v(make_vector(1, 2, 3, 4, 5));
    for(const auto& x : v) std::cout << x;

    return 0;
}