| 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. |
| 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 1 if x is positive infinity, and -1 if x is negative infinity. |
NAME
fpclassify, isfinite, isnormal, isnan, isinf - floating-point classification macros
LIBRARY
Math library (libm, -lm)
SYNOPSIS
#include <math.h>int fpclassify(\nx\n);\n
\nint isfinite(\nx\n);\n
\nint isnormal(\nx\n);\n
\nint isnan(\nx\n);\n
\nint isinf(\nx\n);fpclassify(), isfinite(), isnormal():
\n
_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112Lisnan():
\n
_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
\n
|| _XOPEN_SOURCE
\n
|| /* Since glibc 2.19: */ _DEFAULT_SOURCE
\n
|| /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCEisinf():
\n
_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
\n
|| /* Since glibc 2.19: */ _DEFAULT_SOURCE
\n
|| /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCEDESCRIPTION
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 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 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 |
| fpclassify (), isfinite (), isnormal (), isnan (), isinf () | 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.)
NOTES
For isinf(), the standards merely say that the return value is nonzero if and only if the argument has an infinite value.
SEE ALSO
finite(3), INFINITY(3), isgreater(3), signbit(3)