double zero = 0.0;

double pinf = 1 / zero;
double minf = -pinf;
double ind = pinf - pinf;

std::cout << "nind=" << ind; //-1.#IND

if(ind == std::numeric_limits<double>::infinity())
{
std::cout << "nnинфинити:" << ind;
}

if(ind == -std::numeric_limits<double>::infinity())
{
std::cout << "nnинфинити2:" << ind;
}

if(ind != ind)
{
std::cout << "nnинфинити3:" << ind;
}

std::numeric_limits<double>::is_iec559