GNU/Linux man pages
Livre :
Expressions régulières,
Syntaxe et mise en oeuvre :
GNU/Linux |
Debian 6.0.0(Squeeze) |
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isnormal(3) |
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fpclassify, 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)):
fpclassify(), isfinite(), isnormal():
_XOPEN_SOURCE >= 600
|| _ISOC99_SOURCE ||
_POSIX_C_SOURCE >= 200112L;
or cc -std=c99
isnan():
_BSD_SOURCE || _SVID_SOURCE ||
_XOPEN_SOURCE || _ISOC99_SOURCE ||
_POSIX_C_SOURCE >= 200112L;
or cc -std=c99
isinf():
_BSD_SOURCE || _SVID_SOURCE ||
_XOPEN_SOURCE >= 600 || _ISOC99_SOURCE ||
_POSIX_C_SOURCE >= 200112L;
or cc -std=c99
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:
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FP_NAN |
x is "Not a Number". | ||
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FP_INFINITE |
x is either positive infinity or negative infinity. | ||
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FP_ZERO |
x is zero. | ||
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FP_SUBNORMAL |
x is too small to be represented in normalized format. | ||
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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.
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isfinite(x) |
returns a nonzero value if |
(fpclassify(x) != FP_NAN && fpclassify(x) != FP_INFINITE)
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isnormal(x) |
returns a nonzero value if (fpclassify(x) == FP_NORMAL) | ||
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isnan(x) |
returns a nonzero value if (fpclassify(x) == FP_NAN) | ||
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isinf(x) |
returns 1 if x is positive infinity, and −1 if x is negative infinity. |
C99, POSIX.1.
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.)
finite(3), INFINITY(3), isgreater(3), signbit(3)
This page is part of release 3.27 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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isnormal(3) | |