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); |
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Note |
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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:
FP_NANx is "Not a
Number".
FP_INFINITEx is either
plus or minus infinity.
FP_ZEROx is
zero.
FP_SUBNORMALx is too
small to be represented in normalized format.
FP_NORMALif 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.)
finite(3), INFINITY(3), isgreater(3)
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