ilogb(3)

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

6       ilogb, ilogbf, ilogbl - get integer exponent of a floating-point value
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SYNOPSIS

9       #include <math.h>
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11       int ilogb(double x);
12       int ilogbf(float x);
13       int ilogbl(long double x);
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15       Link with -lm.
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17   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
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19       ilogb():
20           _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 500 ||
21           _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED || _ISOC99_SOURCE ||
22           _POSIX_C_SOURCE >= 200112L;
23           or cc -std=c99
24       ilogbf(), ilogbl():
25           _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 600 ||
26           _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L;
27           or cc -std=c99
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DESCRIPTION

30       These functions return the exponent part of their argument as a  signed
31       integer.   When  no error occurs, these functions are equivalent to the
32       corresponding logb(3) functions, cast to int.
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RETURN VALUE

35       On success, these functions return the exponent of x, as a signed inte‐
36       ger.
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38       If  x  is  zero,  then  a domain error occurs, and the functions return
39       FP_ILOGB0.
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41       If x is a NaN, then a domain error occurs,  and  the  functions  return
42       FP_ILOGBNAN.
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44       If  x  is  negative  infinity or positive infinity, then a domain error
45       occurs, and the functions return INT_MAX.
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ERRORS

48       See math_error(7) for information on how to determine whether an  error
49       has occurred when calling these functions.
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51       The following errors can occur:
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53       Domain error: x is 0 or a NaN
54              An invalid floating-point exception (FE_INVALID) is raised.
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56              These functions do not set errno for this case.
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58       Domain error: x is an infinity
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60              These  functions do not set errno or raise an exception for this
61              case.
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CONFORMING TO

64       C99, POSIX.1-2001.
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COLOPHON

70       This page is part of release 3.53 of the Linux  man-pages  project.   A
71       description  of  the project, and information about reporting bugs, can
72       be found at http://www.kernel.org/doc/man-pages/.
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76                                  2010-09-20                          ILOGB(3)