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 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)

returns a nonzero value if
(fpclassify(x) != FP_NAN && fpclassify(x) != FP_INFINITE)

isnormal(x)

returns a nonzero value if (fpclassify(x) == FP_NORMAL)

isnan(x)

returns a nonzero value if (fpclassify(x) == FP_NAN)

isinf(x)

returns a nonzero value if (fpclassify(x) == FP_INFINITE)

NOTE

On systems conforming to BSD 4.3, isinf() will return 1 for positive, and -1 for negative infinity.

CONFORMING TO

C99

SEE ALSO

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