isfinite - Macro to test for finite value

Syntax	#include <math.h> C11 int isfinite(x); (End)
Description	x has to be an argument of type float, double or long double. The isfinite() macro determines whether its argument has a finite value.
Return val.	0	if x is either Infinity or NaN.
	Value != 0	otherwise.
Notes	In this implementation, isfinite() always returns a value != 0, i.e. all floatingpoint numbers are finite and valid.
See also	fpclassify, isinf, isnan, isnormal, math.h.