Const array initialization if its too long [closed]

Question

In my answer to this question it was mentioned that the code I posted wouldn't work if the variable was declared as const.

What if i want to initialize a long array that's const type

int main (){
    const int ar[100];
 //this is invalid in c++
 //something like this

    for (int i=0;i <100;++i)
        ar[i]=i;
    return 0;
}

Are there other ways to do this than using the #define method proposed in that question?

Answer 1

There's no way to do it directly, without hacks.

In C++ one way to work around this problem is to take advantage of the fact that inside their constructors const objects are still modifiable. So, you can wrap your array into a class and initialize it in the constructor

struct Arr 
{
  int a[100];

  A() 
  {
    for (unsigned i = 0; i < 100; ++i)
      a[i] = i;
  }
};

and then just declare

const Arr arr;

Of course, now you will have to access it as arr.a[i], unless you override the operators in Arr.

Answer 2

You could use a trick... initialize a regular array and then get a reference to a const array:

int arr[100];
for (int i=0; i<100; i++) arr[i] = i*i;

const int (&carr)[100] = arr;