sw::wrapper<vector<T>> vec;  // normal vector
sw::wrapper<vector<T>, false> vec;  // same as above

sw::wrapper<vector<T>, true> vec_on(5, 0);  
// vector with auto-check each operator[] range.
// if illegal, throw std::out_of_range.

vec_on.set_upper(3);    // user-define upper bound
vec_on.set_lower(2);    // user-define lower bound

vec_on[3] = 1;          
// this will throw exception due to index(3) >= upper
// index need to be >= lower and < upper and < size()

sw::wrapper_s<vector<T>, false> vec_s_on(5, 0);
vec_s_on.set_special(0, 1, 3, 4);
// if index hit these special value, throw exception