NaN, Inf, isNaN, isInf – not-a-number and infinity functions

#include <u.h>
#include <libc.h>
double NaN(void)
double Inf(int)
int     isNaN(double)
int     isInf(double, int)

The IEEE floating point standard defines values called ‘not-a-number’ and positive and negative ‘infinity’. These values can be produced by such things as overflow and division by zero. Also, the library functions sometimes return them when the arguments are not in the domain, or the result is out of range.
NaN returns a double that is not-a-number. IsNaN returns true if its argument is not-a-number.
Inf(i) returns positive infinity if i is greater than or equal to zero, else negative infinity. IsInf returns true if its first argument is infinity with the same sign as the second argument.


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