Joe Gottman wrote:
Several libraries have an is_nan() function buried deep in the code. Are there any plans to make a general is_nan function available? This would be quite useful, as well as similar functions like is_finite.
Joe Gottman
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The date_time library contains the following is_nan function: static bool is_nan(const T& x) { return std::numeric_limits<T>::has_quiet_NaN && (x != x); } It has been pointed out by Martin Bonner that this is not safe, for it requires strict IEEE 754 compliance and it may be optimized away by an over-eager optimizing compiler. Here is the implementation I'm currently using: //------------------------------------------------------------------- #if defined(BOOST_MSVC) // Microsoft Visual C++ template<class T> int is_nan(T t) { return _isnan(t); } #elif defined(__GNUC__) // GCC template<class T> int is_nan(T t) { return isnan(t); } #else // generic template<class T> int is_nan(T t) { if(std::numeric_limits<T>::has_infinity) return !(t <= std::numeric_limits<T>::infinity()); else return t != t; } #endif //-------------------------------------------------------------------- Comments? Anyone wants to add more #if's? --Johan Råde