fpclassify

Section: Linux Programmer's Manual (3)
Updated: 2004-10-31
Index Return to Main Contents
 

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);

Compile with -std=c99; link with -lm.  

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 is 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 then it must be a normal floating-point number.

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

isfinite(x)
returns a non-zero value if
(fpclassify(x) != FP_NAN && fpclassify(x) != FP_INFINITE)
isnormal(x)
returns a non-zero value if (fpclassify(x) == FP_NORMAL)
isnan(x)
returns a non-zero value if (fpclassify(x) == FP_NAN)
isinf(x)
returns 1 if x is positive infinity, and -1 if x is negative infinity.
 

NOTE

In glibc 2.01 and earlier, isinf() returns a non-zero value (actually: 1) if x is an infinity (positive or negative). (This is all that C99 requires.)  

CONFORMING TO

C99  

SEE ALSO

finite(3), INFINITY(3), isgreater(3)


 

Index

NAME
SYNOPSIS
DESCRIPTION
NOTE
CONFORMING TO
SEE ALSO

linux.jgfs.net manual pages