Pass std::array as Reference Parameter

Question

I can pass my array directly, but I need to know how to pass it by reference. I'm using the new std::array with type Element. I've tried several things, but they're not working. I'm not sure how to pass it as a reference. I've messed around and I can't figure this out.

How do I pass a std::array as a reference parameter to avoid copying the entire array?

How my array is set up:

std::array<Element, 115> Elements =
{{
    /*int aNumber, float awNumber, period_number PERIOD, group_names GROUP_NAME, metal_status METALSTATUS,
    valence_shell Orbital,std::string eName, std::string eSybol);*/
    {},
    {1,     1.00794,        period::PERIOD_ONE,     group::HYDROGEN,        metal::NONMETAL,    shell::S_ORBITAL,   "Hydrogen",     "H"}
}};

Working

void sortByAtomicNumber(std::array<Element, 115> elements, int minimum, int maximum)
{
    int counter = 1;
    for(;minimum < (maximum+1); minimum++)
    {
        std::cout << counter << ".) " << elements[minimum].getElementName() << std::endl;
        counter++;
    }
}

Tried From: http://gauravpandey.com/wordpress/?p=602 //I haven't learned templates yet...

 template<size_t N>
void sortByAtomicNumber(std::array<int, N> const& arr, int maximum, int minimum) {
    int counter = 1;
    for(;minimum < (maximum+1); minimum++)
    {
        std::cout << counter << ".) " << arr[minimum].getElementName() << std::endl;
        counter++;
    }
}

Error from Above

---

error: passing 'const value_type {aka const Element}' as 'this' argument of 'std::string > > Element::getElementName()' discards qualifiers [-fpermissive]

---

Answer 1

You have some errors:

1. In the template sortByAtomicNumber, std::array<int, N> should be std::array<Element, N>.

2. If you want call a function of a const object, the function must be const. So your arr is const reference, the void getElementName(); of the Element class should be void getElementName() const;.

3. If you want call a non-const function of a object, the object must be non-const. So template<size_t N> void sortByAtomicNumber(std::array<int, N> const& arr, int maximum, int minimum) { /* your code */ } should be template<size_t N> void sortByAtomicNumber(std::array<Element, N>& arr, int maximum, int minimum) { /* your code */ }, like @portforwardpodcast said.

Note: About the const function of const class, you can see this article. Hope that can help you.

Answer 2

Try this:

void sortByAtomicNumber(std::array<Element, 115> &elements, int minimum, int maximum)
{
    int counter = 1;
    for(;minimum < (maximum+1); minimum++)
    {
        std::cout << counter << ".) " << elements[minimum].getElementName() << std::endl;
        counter++;
    }
}

Answer 3

Your function definition looks wrong, the const is in the wrong place: You gave this definition:

template<size_t N>
void sortByAtomicNumber(std::array<int, N> const& arr, int maximum, int minimum)
{
    ...
}

It should be:

template<size_t N>
void sortByAtomicNumber(const std::array<int, N>& arr, int maximum, int minimum)
{
    ...
}