How do you check for infinite and indeterminate values in C++?

Question

In my programs infinity usually arises when a value is divided by zero. I get indeterminate when I divide zero by zero. How do you check for infinite and indeterminate value

Answer 1

You may also use these as a strict C++-only solution. They don't really offer more than the OP's solution except added security through use of type traits and perhaps the tiniest speed boost in the case of is_inf.

template  struct static_assert;
template <> struct static_assert { };

template
inline bool is_NaN(T const& x) {
    static_cast(sizeof(static_assert::has_quiet_NaN>));
    return std::numeric_limits::has_quiet_NaN and (x != x);
}

template 
inline bool is_inf(T const& x) {
    static_cast(sizeof(static_assert::has_infinity>));
    return x == std::numeric_limits::infinity() or x == -std::numeric_limits::infinity();
}

(beware of self-made static_assert)