Output parameters with arrays in one function with Arduino and C ++

I have a problem with the initialization with various parameters in my function.
It works if I have created an array int params [] = {...}. However, it doesn’t work if I want to write the parameters directly into the function.

declaration (in the .h)

void phase_an(int led[]);

in the .cpp

void RS_Schaltung::phase_an(int led[])
{
  for (size_t i = 0; i < LEN(led); i++) {
    digitalWrite(led[i], HIGH);
  }
}

if I try this way, it won’t work. I would like it to be like that. But I couldn’t find anything about it on the internet. …:
in the Arduino sketch:

RS.phase_an(RS.ampelRot, RS.ampelGelb, ..... );    <--- is there a way to do it like that?

what amazes me is that it works this way:

int p_an [5] = {RS.ampelRot, RS.ampelGelb, RS.ampelGruen, RS.rot, RS.gelb};
...................
RS.phase_an (p_an);

does anyone have a suggestion?

>Solution :

There are several ways of making a function accepting a variable number of arguments here.

However, in your current code there is a problem: when you pass a native array of unknown size as argument of a function (e.g. void f(int a[])), the argument will be managed a pointer to an array, and there is no way inside this function to know the real length of that array. I don’t know how LEN() is defined, but chances are high that it doesn’t works well in your code.

A safer and more practical alternative is to use a vector<int> instead:

#include <iostream>
#include <vector>
using namespace std;

void f(const vector<int>& a){
    for (int i=0; i<a.size(); i++) {
        cout<<a[i]<<" ";
    }
    cout<<endl; 
}

int main() {
    vector<int> test={1,2,3,4}; 
    f(test); 
    f({1,2,3,4});
    return 0;
}

In this case, you can pass your multiple values between bracket in the function call (e.g. ({RS.ampelRot, RS.ampelGelb, RS.ampelGruen, RS.rot, RS.gelb})and C++ will automatically convert it to a vector.