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

6       fpclassify, isfinite, isnormal, isnan, isinf - floating-point classifi‐
7       cation 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       Link with -lm.
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24   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
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26       fpclassify(), isfinite(), isnormal(): _XOPEN_SOURCE >= 600 ||
27       _ISOC99_SOURCE; or cc -std=c99
28       isnan(): _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE ||
29       _ISOC99_SOURCE; or cc -std=c99
30       isinf(): _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 600 ||
31       _ISOC99_SOURCE; or cc -std=c99
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DESCRIPTION

34       Floating  point  numbers  can  have special values, such as infinite or
35       NaN.  With the macro fpclassify(x) you can find out  what  type  x  is.
36       The  macro takes any floating-point expression as argument.  The result
37       is one of the following values:
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39       FP_NAN        x is "Not a Number".
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41       FP_INFINITE   x is either positive infinity or negative infinity.
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43       FP_ZERO       x is zero.
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45       FP_SUBNORMAL  x is too small to be represented in normalized format.
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47       FP_NORMAL     if nothing of the above is correct then it must be a nor‐
48                     mal floating-point number.
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50       The other macros provide a short answer to some standard questions.
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52       isfinite(x)   returns a nonzero value if
53                     (fpclassify(x) != FP_NAN && fpclassify(x) != FP_INFINITE)
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55       isnormal(x)   returns a nonzero value if (fpclassify(x) == FP_NORMAL)
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57       isnan(x)      returns a nonzero value if (fpclassify(x) == FP_NAN)
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59       isinf(x)      returns 1 if x is positive infinity, and -1 if x is nega‐
60                     tive infinity.
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CONFORMING TO

63       C99, POSIX.1.
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65       For isinf(), the standards merely say that the return value is  nonzero
66       if and only if the argument has an infinite value.
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NOTES

69       In  glibc  2.01 and earlier, isinf() returns a nonzero value (actually:
70       1) if x is positive infinity or negative infinity.  (This is  all  that
71       C99 requires.)
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SEE ALSO

74       finite(3), INFINITY(3), isgreater(3), signbit(3)
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COLOPHON

77       This  page  is  part of release 3.25 of the Linux man-pages project.  A
78       description of the project, and information about reporting  bugs,  can
79       be found at http://www.kernel.org/doc/man-pages/.
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83                                  2008-08-07                     FPCLASSIFY(3)