infnan man page
infnan — deal with infinite or not-a-number (NaN) result
#include <math.h> double infnan(int error);
Link with -lm.
The infnan() function returns a suitable value for infinity and "not-a-number" (NaN) results. The value of error can be ERANGE to represent infinity or anything else to represent NaN. errno is also set.
If error is ERANGE (Infinity), HUGE_VAL is returned.
If error is -ERANGE (-Infinity), -HUGE_VAL is returned.
If error is anything else, NAN is returned.
The value of error is "not-a-number" (NaN).
The value of error is positive infinity or negative infinity.
This obsolete function was provided in libc4 and libc5, but is not available in glibc2.
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