plan9 man page for nan

NAN(2)								System Calls Manual							    NAN(2)

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

SYNOPSIS
       #include <u.h>
       #include <libc.h>

       double NaN(void)

       long   Inf(int)

       int    isNaN(double)

       int    isInf(double, int)

DESCRIPTION
       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.

SOURCE
       /sys/src/libc/$objtype/nan.c

																	    NAN(2)