static void compare_numbers(
    char const* description, T1 const& expected, T2 const& actual)
{
    if (expected != actual)
    {
        std::cerr << description << ": expected = " << expected
                  << "; actual = " << actual << std::endl;
    }
}
static void compare_numbers(
    char const* description, T1 const& expected, T2 const& actual)
{
    if (expected != actual)
    {
        std::cerr << description << ": expected = " << expected
                  << "; actual = " << actual << std::endl;
    }
}