Template class copy constructor

Question

I want to write copy constructor for a template class. I have this class:

template<int C>
class Word {
    array<int, C> bitCells; //init with zeros
    int size;

public:
    //constructor fill with zeros
    Word<C>() {
        //bitCells = new array<int,C>;
        for (int i = 0; i < C; i++) {
            bitCells[i] = 0;
        }
        size = C;
    }
    Word<C>(const Word<C>& copyObg) {
        size=copyObg.getSize();
        bitCells=copyObg.bitCells;
    }
}

I have errors with the copy constructor, on the line of intilizeing the size, I get: "Multiple markers at this line - passing 'const Word<16>' as 'this' argument of 'int Word::getSize() [with int C = 16]' discards qualifiers [- fpermissive] - Invalid arguments ' Candidates are: int getSize() '"

what is wrong with this ? thank you

Answer 1

I'd write the class like this:

template <std::size_t N>
class Word
{
    std::array<int, N> bit_cells_;

public:
    static constexpr std::size_t size = N;

    Word() : bit_cells_{} {}

    // public functions
};

Note:

• No need for a dynamic size, since it's part of the type.

• No need for special member functions, since the implicitly defined ones are fine.

• Initialize the member array to zero via the constructor-initializer-list.

• Template parameter is unsigned, since it represents a count.

Answer 2

What's wrong is that your getSize() is not declared const . Make it so:

int getSize() const { return size; }