fpclassify(3) Linux Programmer s Manual fpclassify(3)

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.)


SEE ALSO finite(3), INFINITY(3), isgreater(3)

2004-10-31 fpclassify(3)