posix man page for logbf

LOGB(P) 						     POSIX Programmer's Manual							   LOGB(P)

NAME
       logb, logbf, logbl - radix-independent exponent

SYNOPSIS
       #include <math.h>

       double logb(double x);
       float logbf(float x);
       long double logbl(long double x);

DESCRIPTION
       These functions shall compute the exponent of x, which is the integral part of log_r |x|, as a signed floating-point value, for non-zero x,
       where r is the radix of the machine's floating-point arithmetic, which is the value of FLT_RADIX defined in the <float.h> header.

       If x is subnormal it is treated as though it were normalized; thus for finite positive x:

	      1 <= x * FLT_RADIX**-logb(x) < FLT_RADIX

       An application wishing to check for error situations should set errno to zero and call feclearexcept(FE_ALL_EXCEPT)  before  calling  these
       functions.   On	return, if errno is non-zero or fetestexcept(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is non-zero, an error
       has occurred.

RETURN VALUE
       Upon successful completion, these functions shall return the exponent of x.

       If x is +-0, a pole error shall occur and logb(), logbf(), and logbl() shall return -HUGE_VAL, -HUGE_VALF, and -HUGE_VALL, respectively.

       If x is NaN, a NaN shall be returned.

       If x is +-Inf, +Inf shall be returned.

ERRORS
       These functions shall fail if:

       Pole Error
	      The value of x is +-0.

       If the integer expression (math_errhandling & MATH_ERRNO) is non-zero, then errno shall be set  to  [ERANGE].  If  the  integer	expression
       (math_errhandling & MATH_ERREXCEPT) is non-zero, then the divide-by-zero floating-point exception shall be raised.

       The following sections are informative.

EXAMPLES
       None.

APPLICATION USAGE
       On  error,  the	expressions  (math_errhandling & MATH_ERRNO) and (math_errhandling & MATH_ERREXCEPT) are independent of each other, but at
       least one of them must be non-zero.

RATIONALE
       None.

FUTURE DIRECTIONS
       None.

SEE ALSO
       feclearexcept() , fetestexcept() , ilogb() , scalb() , the Base Definitions volume of  IEEE Std 1003.1-2001,  Section  4.18,  Treatment	of
       Error Conditions for Mathematical Functions, <float.h>, <math.h>

COPYRIGHT
       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Standard for Information Technol-
       ogy -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
       Electrical  and	Electronics  Engineers, Inc and The Open Group. In the event of any discrepancy between this version and the original IEEE
       and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can  be  obtained
       online at http://www.opengroup.org/unix/online.html .

IEEE
/The Open Group						       2003								   LOGB(P)