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man:ilogb

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

NAME

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

SYNOPSIS

     #include <math.h>
     int ilogb(double x);
     int ilogbf(float x);
     int ilogbl(long double x);
     Link with -lm.
 Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
     ilogb():
         _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
             || _XOPEN_SOURCE >= 500
             || /* Since glibc 2.19: */ _DEFAULT_SOURCE
             || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
     ilogbf(), ilogbl():
         _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
             || /* Since glibc 2.19: */ _DEFAULT_SOURCE
             || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

DESCRIPTION

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

RETURN VALUE

     On success, these functions return the exponent of x, as a signed inte-
     ger.
     If x is zero, then a domain error  occurs,  and  the  functions  return
     FP_ILOGB0.
     If  x  is  a  NaN, then a domain error occurs, and the functions return
     FP_ILOGBNAN.
     If x is negative infinity or positive infinity,  then  a  domain  error
     occurs, and the functions return INT_MAX.

ERRORS

     See  math_error(7) for information on how to determine whether an error
     has occurred when calling these functions.
     The following errors can occur:
     Domain error: x is 0 or a NaN
            An invalid floating-point exception (FE_INVALID) is raised,  and
            errno is set to EDOM (but see BUGS).
     Domain error: x is an infinity
            An  invalid floating-point exception (FE_INVALID) is raised, and
            errno is set to EDOM (but see BUGS).

ATTRIBUTES

     For  an  explanation  of  the  terms  used   in   this   section,   see
     attributes(7).
     +----------------------------+---------------+---------+
     |Interface                   | Attribute     | Value   |
     +----------------------------+---------------+---------+
     |ilogb(), ilogbf(), ilogbl() | Thread safety | MT-Safe |
     +----------------------------+---------------+---------+

CONFORMING TO

     C99, POSIX.1-2001, POSIX.1-2008.

BUGS

     Before version 2.16, the following bugs existed in the glibc  implemen-
     tation of these functions:
  • The domain error case where x is 0 or a NaN did not cause errno to

be set or (on some architectures) raise a floating-point exception.

  • The domain error case where x is an infinity did not cause errno to

be set or raise a floating-point exception.

SEE ALSO

     log(3), logb(3), significand(3)

COLOPHON

     This page is part of release 4.16 of the Linux  man-pages  project.   A
     description  of  the project, information about reporting bugs, and the
     latest    version    of    this    page,    can     be     found     at
     https://www.kernel.org/doc/man-pages/.
                                2017-09-15                          ILOGB(3)
/data/webs/external/dokuwiki/data/pages/man/ilogb.txt · Last modified: 2019/05/17 09:32 by 127.0.0.1

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