Default function that just returns the passed value?

Question

As a lazy developer, I like to use this trick to specify a default function:

template 

        

Answer 1

A way to deal with this is to have two different functions. I find quite sane not to use default parameters.

template 
void index(std::array &x, Function&& f){
    for(unsigned int i = 0; i < Size; ++i) x[i] = f(i);
}

template
void index(std::array &x){
    return index(x, [](unsigned int i){return i;});                      // C++11 in this case
                //, [](auto&& e){return std::forward(e)};); // C++14 in a more general case
                //, std::identity); // C++20 in general
}