fpclassify, isfinite, isnormal, isnan, isinf — floating-point classification macros
Floating point numbers can have special values, such as
infinite or NaN. With the macro
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
x is either
positive infinity or negative infinity.
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
For an explanation of the terms used in this section, see attributes(7).
POSIX.1-2001, POSIX.1-2008, C99.
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:
x is positive
infinity or negative infinity. (This is all that C99
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Copyright 2002 Walter Harms (walter.harmsinformatik.uni-oldenburg.de)
Distributed under GPL
This was done with the help of the glibc manual.
2004-10-31, aeb, corrected