GNU/Linux man pages
Livre :
Expressions régulières,
Syntaxe et mise en oeuvre :
GNU/Linux |
CentOS 5.2 |
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isnan(3) |
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fpclassify, isfinite, isnormal, isnan − floating-point classification macros
#include <math.h>
int fpclassify(x);
int isfinite(x);
int isnormal(x);
int isnan(x);
int isinf(x);
Compile with −std=c99; link with −lm.
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". |
FP_INFINITE
x is either plus or minus 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.
In glibc 2.01 and earlier, isinf() returns a non-zero value (actually: 1) if x is an infinity (positive or negative). (This is all that C99 requires.)
C99
finite(3), INFINITY(3), isgreater(3)
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isnan(3) | |