Manual Section... (3) - page: isinf
NAMEfpclassify, isfinite, isnormal, isnan, isinf - floating-point classification macros
#include <math.h> int fpclassify(x); int isfinite(x); int isnormal(x); int isnan(x); int isinf(x);
Link with -lm.
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
_XOPEN_SOURCE >= 600 || _ISOC99_SOURCE; or
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
DESCRIPTIONFloating 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.
CONFORMING TOC99, POSIX.1.
NOTESIn 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.)
SEE ALSOfinite(3), INFINITY(3), isgreater(3), signbit(3)
COLOPHONThis page is part of release 3.24 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/.
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Time: 15:27:06 GMT, June 11, 2010