Passing around fixed-size arrays in C++?

Question

Basically I'd like to do something like that:

int[3] array_func()
{
    return {1,1,1};
}

int main(int argc,char * argv[])
{
    int[3] point=array_func();
}

But that doesn't seem legal in C++. I know I can use vectors, but since I know the size of the array is a constant, it seems like a loss of performance is likely to occur. I'd also like to avoid a new if I can, because allocating stuff on the stack is easier and also likely to improve performance.

What's the solution here?

Answer 1

Using C++0x, the almost finalized new C++ standard (already implemented in latest gcc and msvc IIRC), you can do it exactly as you want! Simply use std::array instead of int[3].

std::array<int, 3> array_func()
{
    return {1,1,1};
}

int main(int argc,char * argv[])
{
    std::array<int, 3> point = array_func();
}

Answer 2

Put the array into a struct. boost::array is such a package:

boost::array<int, 3> array_func() {
  boost::array<int, 3> a = {{ 1, 1, 1 }};
  return a;
}

int main() {
  boost::array<int, 3> b = array_func();
}

Quick and dirty:

template<typename E, size_t S>
struct my_array {
  E data[S];
};

Notice how you can use aggregate initialization syntax.