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



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

SYNOPSIS
       #include <&lt;math.h>&gt;

       int ilogb(double x);
       int ilogbf(float x);
       int ilogbl(long double x);

       Link with -lm.

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).  An error will occur
       for zero and infinity and NaN, and possibly for overflow.

ERRORS
       In order to check for errors, set errno to  zero  and  call  feclearex-
       cept(FE_ALL_EXCEPT)  before  calling  these  functions.   On return, if
       errno is non-zero or fetestexcept(FE_INVALID | FE_DIVBYZERO |  FE_OVER-
       FLOW | FE_UNDERFLOW) is non-zero, an error has occurred.

       If  an  error  occurs  and (math_errhandling &amp; MATH_ERRNO) is non-zero,
       then errno is set to EDOM.  If an error occurs and (math_errhandling  &amp;
       MATH_ERREXCEPT)  is non-zero, then the invalid floating-point exception
       is raised.

       A domain error occurs when x is zero or infinite (or too large, or  too
       small) or NaN.  If x is zero, the constant FP_ILOGB0 is returned.  If x
       is NaN, the constant FP_ILOGBNAN is returned.  If x is infinite (or too
       large), INT_MAX is returned.  If x is too small, INT_MIN is returned.

CONFORMING TO
       C99.

SEE ALSO
       log(3), logb(3)

COLOPHON
       This  page  is  part of release 3.05 of the Linux man-pages project.  A
       description of the project, and information about reporting  bugs,  can
       be found at http://www.kernel.org/doc/man-pages/.



                                  2004-10-31                          ILOGB(3)