opensolaris man page for log2l

log2(3M)						  Mathematical Library Functions						  log2(3M)

NAME
       log2, log2f, log2l - compute base 2 logarithm functions

SYNOPSIS
       c99 [ flag... ] file... -lm [ library... ]
       #include <math.h>

       double log2(double x);

       float log2f(float x);

       long double log2l(long double x);

DESCRIPTION
       These functions compute the base 2 logarithm of their argument x, log2(x).

RETURN VALUES
       Upon successful completion, these functions return the base 2 logarithm of x.

       If x is +-0, a pole error occurs and log2(), log2f(), and log2l() return -HUGE_VAL, -HUGE_VALF, and -HUGE_VALL, respectively.

       For finite values of x that are less than 0,  or if x is -Inf a domain error occurs and a NaN is returned.

       If x is NaN, a NaN is returned.

       If x is 1, +0 is returned.

       If x is +Inf, x is returned.

ERRORS
       These functions will fail if:

       Domain Error    The finite value of x is less than 0, or x is -Inf.

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

       Pole Error      The value of x is 0.

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

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.

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), log(3M), math.h(3HEAD), attributes(5), standards(5)

SunOS 5.11							    12 Jul 2006 							  log2(3M)