Johan Råde wrote:
Floating point numbers can be classified into four categories:
1. finite numbers 2. infinity 3. negative infinity 4. not-a-number (nan)
So maybe we need functions:
[snip] template<class T> bool is_infinity(T a) { return std::numeric_limits<T>::has_infinity && a == std::numeric_limits<T>::infinity(); }
[snip]
You test for negative infinity by calling is_infinity(-a).
...for which it would be easy enough to provide a convenience function (perhaps "is_minus_infinity"), which would just be a wrapper around "is_infinity". Another useful convenience function would be "is_infinite", which would return true if and only if the number was equal to plus or minus infinity (making use of either "is_finite" or both "is_infinity" and "is_minus_infinity") The similarity of the names of "is_infinity" and "is_infinite" might be a problem, but the former could be changed to "is_plus_infinity" to give symmetry with "is_minus_infinity". Paul