Initialize array in constructor without using default constructor or assignment

Question

Consider:

struct A {

 A (int);

 A (const A &);
};

struct B {

 A foo [2];

 B (const A & x, const A & y)
 : foo {x, y} /* HERE IS THE PROBLEM          


        

Answer 1

You can use boost::array. It has a plain native array inside, so it still has the same memory layout like in your example.

struct B {
 boost::array foo;

 B (const A & x, const A & y)
 : foo(createFoo(x, y))
 {}

private:
 static boost::array createFoo(const A & x, const A & y) {
   boost::array a = {{ x, y }};
   return a;
 }
};

If you don't have boost you can create your own array class or use std::tr1 if your compiler has it

template
struct array {
  T data[N];
};

That's all you need, but you can add the usual begin, end, size functions and so on to make it more comfortable to use.