isnormal(3) -- Linux man page

 

NAME

fpclassify, isfinite, isnormal, isnan - floating-point classification macros  

SYNOPSIS

#include <math.h>

int fpclassify(x);

int isfinite(x);

int isnormal(x);

int isnan(x);

int isinf(x);
 

DESCRIPTION

Floating point numbers can have special values, such as infinite or NaN. With the macro fpclassify(x) you can find out what type x is. The macro takes any floating-point expression as argument. The result takes one of the following values:
FP_NAN
x is "Not a Number".
FP_INFINITE
x is either plus or minus infinity.
FP_ZERO
x is zero.
FP_SUBNORMAL
x is too small to be represented in normalized format.
FP_NORMAL
if nothing of the above is correct that it must be a normal floating-point number.

The other macros provide a short answer to some standard questions.

isfinite(x)
(fpclassify(x) != FP_NAN && fpclassify(x) != FP_INFINITE)
isnormal(x)
(fpclassify(x) == FP_NORMAL)
isnan(x)
(fpclassify(x) == FP_NAN)
isinf(x)
(fpclassify(x) == FP_INFINITE)
 

NOTE

 

CONFORMING TO

C99  

SEE ALSO

isgreater(3), isinf(3)