sunos man page for logb

logb(3M)						  Mathematical Library Functions						  logb(3M)

NAME
       logb, logbf, logbl - radix-independent exponent

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

       double logb(double x);

       float logbf(float x);

       long double logbl(long double x);

DESCRIPTION
       These  functions compute 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, which is the value of FLT_RADIX defined in the <float.h> header.

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

       If x is subnormal:

	 o  For SUSv3-conforming applications (see standards(5)), the exponent of x as if x were normalized is returned.

	 o  Otherwise, -1022, -126, and -16382 are returned for logb(), logbf(), and logbl(), respectively.

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

       If x is NaN, a NaN is returned.

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

ERRORS
       These functions will fail if:

       Pole Error      The value of x is +-0.

		       If the integer expression (math_errhandling & MATH_ERREXCEPT) is non-zero, the divide-by-zero floating-point  exception	is
		       raised.

		       The logb() function sets errno to EDOM if the value of x is 0.

USAGE
       An  application	wanting  to  check  for  exceptions should call feclearexcept(FE_ALL_EXCEPT) before calling these functions. On return, if
       fetestexcept(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is non-zero, an exception  has  been  raised.  An  application  should
       either examine the return value or check the floating point exception flags to detect exceptions.

       An  application	can  also  set	errno  to 0 before calling logb(). On return, if errno is non-zero, an error has occurred. The logbf() and
       logbl() functions do not set errno.

ATTRIBUTES
       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Interface Stability	     |Standard			   |
       +-----------------------------+-----------------------------+
       |MT-Level		     |MT-Safe			   |
       +-----------------------------+-----------------------------+

SEE ALSO
       feclearexcept(3M), fetestexcept(3M), ilogb(3M), math.h(3HEAD), matherr(3M), scalb(3M), attributes(5), standards(5)

SunOS 5.10							    1 Nov 2003								  logb(3M)