fpclassify, isfinite, isnormal, isnan, isinf - floating-point classification macros
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L || _XOPEN_SOURCE || /* Since glibc 2.19: */ _DEFAULT_SOURCE || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L || /* Since glibc 2.19: */ _DEFAULT_SOURCE || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
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:
x is "Not a Number".
x is either positive infinity or negative infinity.
x is zero.
x is too small to be represented in normalized format.
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.
For an explanation of the terms used in this section, see attributes(7).
|fpclassify(), isfinite(), isnormal(), isnan(), isinf()||Thread safety||MT-Safe|
POSIX.1-2001, POSIX.1-2008, C99.
For isinf(), the standards merely say that the return value is nonzero if and only if the argument has an infinite value.
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.)
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