1FPCLASSIFY(3)              Linux Programmer's Manual             FPCLASSIFY(3)
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NAME

6       fpclassify,  isfinite,  isnormal, isnan - floating-point classification
7       macros
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SYNOPSIS

10       #include <math.h>
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12       int fpclassify(x);
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14       int isfinite(x);
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16       int isnormal(x);
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18       int isnan(x);
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20       int isinf(x);
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22       Compile with -std=c99; link with -lm.
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DESCRIPTION

25       Floating point numbers can have special values,  such  as  infinite  or
26       NaN.  With the macro fpclassify(x) you can find out what type x is. The
27       macro takes any floating-point expression as argument.  The  result  is
28       one of the following values:
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30       FP_NAN x is "Not a Number".
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32       FP_INFINITE
33              x is either plus or minus infinity.
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35       FP_ZERO
36              x is zero.
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38       FP_SUBNORMAL
39              x is too small to be represented in normalized format.
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41       FP_NORMAL
42              if  nothing  of  the  above  is correct then it must be a normal
43              floating-point number.
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45       The other macros provide a short answer to some standard questions.
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47       isfinite(x)
48              returns a non-zero value if
49              (fpclassify(x) != FP_NAN && fpclassify(x) != FP_INFINITE)
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51       isnormal(x)
52              returns a non-zero value if (fpclassify(x) == FP_NORMAL)
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54       isnan(x)
55              returns a non-zero value if (fpclassify(x) == FP_NAN)
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57       isinf(x)
58              returns 1 if x is positive infinity, and -1  if  x  is  negative
59              infinity.
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NOTE

62       In  glibc 2.01 and earlier, isinf() returns a non-zero value (actually:
63       1) if x is an infinity (positive or negative).  (This is all  that  C99
64       requires.)
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CONFORMING TO

67       C99
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SEE ALSO

70       finite(3), INFINITY(3), isgreater(3)
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75                                  2004-10-31                     FPCLASSIFY(3)