ilogb(3) - f14

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(): _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 500 ||
20       _ISOC99_SOURCE; or cc -std=c99
21       ilogbf(), ilogbl(): _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 600
22       || _ISOC99_SOURCE; or cc -std=c99
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DESCRIPTION

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

30       On success, these functions return the exponent of x, as a signed inte‐
31       ger.
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33       If x is zero, then a domain error  occurs,  and  the  functions  return
34       FP_ILOGB0.
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36       If  x  is  a  NaN, then a domain error occurs, and the functions return
37       FP_ILOGBNAN.
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39       If x is negative infinity or positive infinity,  then  a  domain  error
40       occurs, and the functions return INT_MAX.
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ERRORS

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

59       C99, POSIX.1-2001.
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COLOPHON

65       This  page  is  part of release 3.25 of the Linux man-pages project.  A
66       description of the project, and information about reporting  bugs,  can
67       be found at http://www.kernel.org/doc/man-pages/.
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71                                  2009-02-04                          ILOGB(3)