initialize a const array in a class initializer in C++


Question

I have the following class in C++:

class a {
    const int b[2];
    // other stuff follows

    // and here's the constructor
    a(void);
}

The question is, how do I initialize b in the initialization list, given that I can't initialize it inside the body of the function of the constructor, because b is const?

This doesn't work:

a::a(void) : 
    b([2,3])
{
     // other initialization stuff
}

Edit: The case in point is when I can have different values for b for different instances, but the values are known to be constant for the lifetime of the instance.

1
71
4/7/2013 12:20:28 PM

Accepted Answer

Like the others said, ISO C++ doesn't support that. But you can workaround it. Just use std::vector instead.

int* a = new int[N];
// fill a

class C {
  const std::vector<int> v;
public:
  C():v(a, a+N) {}
};
32
10/2/2008 1:52:14 PM

With C++11 the answer to this question has now changed and you can in fact do:

struct a {
    const int b[2];
    // other bits follow

    // and here's the constructor
    a();
};

a::a() :
    b{2,3}
{
     // other constructor work
}

int main() {
 a a;
}

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