fpclassify(),
isfinite(),
isnormal():
_XOPEN_SOURCE >= 600 || _ISOC99_SOURCE; or
cc -std=c99 isnan():
_BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE || _ISOC99_SOURCE; or
cc -std=c99 isinf():
_BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 600 || _ISOC99_SOURCE; or
cc -std=c99
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 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.
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.
CONFORMING TO
C99, POSIX.1.
For
isinf(),
the standards merely say that the return value is non-zero
if and only if the argument has an infinite value.
NOTES
In glibc 2.01 and earlier,
isinf()
returns a non-zero value (actually: 1) if
x
is positive infinity or negative infinity.
(This is all that C99 requires.)
This page is part of release 3.14 of the Linux
man-pages
project.
A description of the project,
and information about reporting bugs,
can be found at
http://www.kernel.org/doc/man-pages/.
