Variable number of parameters in function in C++

Question

How I can have variable number of parameters in my function in C++.

Analog in C#:

public void Foo(params int[] a) {
    for (int i = 0; i < a.Leng         


        

Answer 1

The real C++ solution is variadic templates. You'll need a fairly recent compiler and enable C++11 support if needed.

Two ways to handle the "do the same thing with all function arguments" problem: recursively, and with an ugly (but very very Standards compliant) solution.

The recursive solution looks somewhat like this:

template
void print(ArgTypes... args);
template
void print(T t, ArgTypes... args)
{
  std::cout << t;
  print(args...);
}
template<> void print() {} // end recursion

It generates one symbol for each collection of arguments, and then one for each step into the recursion. This is suboptimal to say the least, so the awesome C++ people here at SO thought of a great trick abusing the side effect of a list initialization:

struct expand_type {
  template
  expand_type(T&&...) {}
};
template
void print(ArgTypes... args)
{ 
  expand_type{ 0, (std::cout << args, 0)... };
}

Code isn't generated for a million slightly different template instantiations, and as a bonus, you get preserved order of you function arguments. See the other answer for the nitty gritty details of this solution.