1FPCLASSIFY(3)              Linux Programmer's Manual             FPCLASSIFY(3)
2
3
4

NAME

6       fpclassify, isfinite, isnormal, isnan, isinf - floating-point classifi‐
7       cation macros
8

SYNOPSIS

10       #include <math.h>
11
12       int fpclassify(x);
13
14       int isfinite(x);
15
16       int isnormal(x);
17
18       int isnan(x);
19
20       int isinf(x);
21
22       Link with -lm.
23
24   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
25
26       fpclassify(), isfinite(), isnormal():
27           _XOPEN_SOURCE >= 600 || _ISOC99_SOURCE ||
28           _POSIX_C_SOURCE >= 200112L;
29           or cc -std=c99
30       isnan():
31           _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE || _ISOC99_SOURCE ||
32           _POSIX_C_SOURCE >= 200112L;
33           or cc -std=c99
34       isinf():
35           _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 600 ||
36           _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L;
37           or cc -std=c99
38

DESCRIPTION

40       Floating  point  numbers  can  have special values, such as infinite or
41       NaN.  With the macro fpclassify(x) you can find out  what  type  x  is.
42       The  macro takes any floating-point expression as argument.  The result
43       is one of the following values:
44
45       FP_NAN        x is "Not a Number".
46
47       FP_INFINITE   x is either positive infinity or negative infinity.
48
49       FP_ZERO       x is zero.
50
51       FP_SUBNORMAL  x is too small to be represented in normalized format.
52
53       FP_NORMAL     if nothing of the above is correct then it must be a nor‐
54                     mal floating-point number.
55
56       The other macros provide a short answer to some standard questions.
57
58       isfinite(x)   returns a nonzero value if
59                     (fpclassify(x) != FP_NAN && fpclassify(x) != FP_INFINITE)
60
61       isnormal(x)   returns a nonzero value if (fpclassify(x) == FP_NORMAL)
62
63       isnan(x)      returns a nonzero value if (fpclassify(x) == FP_NAN)
64
65       isinf(x)      returns 1 if x is positive infinity, and -1 if x is nega‐
66                     tive infinity.
67

CONFORMING TO

69       C99, POSIX.1.
70
71       For isinf(), the standards merely say that the return value is  nonzero
72       if and only if the argument has an infinite value.
73

NOTES

75       In  glibc  2.01 and earlier, isinf() returns a nonzero value (actually:
76       1) if x is positive infinity or negative infinity.  (This is  all  that
77       C99 requires.)
78

SEE ALSO

80       finite(3), INFINITY(3), isgreater(3), signbit(3)
81

COLOPHON

83       This  page  is  part of release 3.53 of the Linux man-pages project.  A
84       description of the project, and information about reporting  bugs,  can
85       be found at http://www.kernel.org/doc/man-pages/.
86
87
88
89                                  2010-09-20                     FPCLASSIFY(3)
Impressum