logb(3M)

NAME

     logb - radix-independent exponent

SYNOPSIS

     cc [ flag ... ] file ... -lm [ library ... ]
     #include <math.h>

     double logb(double x);

DESCRIPTION

     The logb() function computes the exponent of x, which is the
     integral part of logr |x|, as a signed floating point value,
     for non-zero x, where  r  is  the  radix  of  the  machine's
     floating-point arithmetic.

RETURN VALUES

     Upon successful completion, logb() returns the  exponent  of
     x.

     If x is 0.0, logb() returns  -HUGE_VAL  and  sets  errno  to
     EDOM.

     If x is _Inf, logb() returns +Inf.

     If x is NaN, logb() returns NaN.

     For exceptional cases, matherr(3M) tabulates the  values  to
     be returned as dictated by various Standards.

ERRORS

     The logb() function will fail if:

     EDOM  The x argument is 0.0.

ATTRIBUTES

     See attributes(5) for descriptions of the  following  attri-
     butes:

     ____________________________________________________________
    |       ATTRIBUTE TYPE        |       ATTRIBUTE VALUE       |
    |_____________________________|_____________________________|
    | MT-Level                    | MT-Safe                     |
    |_____________________________|_____________________________|

SEE ALSO

     ilogb(3M), matherr(3M), attributes(5)