//class header file boost::multi_array<char, 2> array2d;
//class cpp file //at class constructor array2d = boost::multi_array<char,2>(boost::extents[x][y]);
I think the problem is that the last line quoted above is an assignment, not an initialisation: if you look in the boost headers, you'll see the assignment operator is very different from the copy constructor. Basically if you have a constructor that first default-constructs array2d, then you'll have an empty array. Then assigning to it, means you are trying a deep-copy from a x-by-y array to a 0-by-0 array. One way to fix it is to add a line: //at class constructor array2d.resize(boost::extents[x][y]); array2d = boost::multi_array<char,2>(boost::extents[x][y]); Otherwise, you can initialise array2d before the constructor body. Yung-Chin