Undefined number of arguments in C++ [duplicate]

Answer 1

You can use variadic template arguments and tuples:

#include 
#include 

template 
void f(Args&&... args)
{
    auto arguments = std::make_tuple(std::forward(args)...);
    std::cout << std::get<0>(arguments);
}

void f() {} // for 0 arguments

int main()
{
    f(2, 4, 6, 8);
}

Live Demo

For bounds checking, try the following:

#include 
#include 

template 
struct input
{
    std::tuple var;
    input(T&&... t) : var(std::forward(t)...) {}

    template ::value>
    auto get() -> typename std::tuple_element>::type
    {
        return std::get(var);
    }
};

template 
void f(Args&&... args)
{
    auto arguments = input(std::forward(args)...);

    std::cout << arguments.template get<9>();
}

void f() {} // for 0 arguments

int main()
{
    f(2, 4, 6, 8);
}

---

Update: If you need the first argument then you simply want a function which exposes that first argument by separating it from the parameter pack:

template
void foo(Head&& head, Tail&&... tail);

If this is not satisfactory (i.e you want to get the nth-argument), you can unpack the arguments into a std::tuple<> and retrieve an element with std::get<>:

template
void foo(Args&&... args)
{
    auto t = std::forward_as_tuple(std::forward(args)...);
    print(std::get<5>(t));
}