Name
fpclassify, isfinite, isnormal, isnan, isinf - floating-point classification macrosLibrary
Math library ( libm ", " -lm )Synopsis
#include <math.h> int fpclassify( x );
int isfinite( x );
int isnormal( x );
int isnan( x );
int isinf( x );
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
fpclassify() isfinite() isnormal()
_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
isnan()
_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L || _XOPEN_SOURCE || /* Since glibc 2.19: */ _DEFAULT_SOURCE || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
isinf()
_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L || /* Since glibc 2.19: */ _DEFAULT_SOURCE || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
Description
Floating point numbers can have special values, such as infinite or NaN. With the macro 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 positive infinity or negative 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.
returns a nonzero value if (fpclassify(x) != FP_NAN && fpclassify(x) != FP_INFINITE)
returns a nonzero value if (fpclassify(x) == FP_NORMAL)
returns a nonzero value if (fpclassify(x) == FP_NAN)
returns 1 if x is positive infinity, and -1 if x is negative infinity.
Attributes
For an explanation of the terms used in this section, see attributes(7).Interface | Attribute | Value |
T} | Thread safety | MT-Safe |
Standards
C11, POSIX.1-2008.History
POSIX.1-2001, C99.In glibc 2.01 and earlier, isinf() returns a nonzero value (actually: 1) if x is positive infinity or negative infinity. (This is all that C99 requires.)