Mathematical Library Functions                           log2(3M)



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

SYNOPSIS
     c99 [ flag... ] file... -lm [ library... ]
     #include 

     double log2(double x);


     float log2f(float x);


     long double log2l(long double x);


DESCRIPTION
     These functions compute the base 2 logarithm of their  argu-
     ment 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   -HUGEVAL,  -HUGEVALF,  and  -HUGEVAL,
     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.

ERORS
     These functions will fail if:

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

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




SunOS 5.11          Last change: 12 Jul 2006                    1






Mathematical Library Functions                           log2(3M)



     Pole Error      The value of x is 0.

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


USAGE
     An application wanting to check for exceptions  should  call
     feclearexcept(FEALEXCEPT) before calling these functions.
     On  return,  if  fetestexcept(FEINVALID    FEDIVBYZERO  
     FEOVERFLOW    FEUNDERFLOW)  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.

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



     
           ATRIBUTE TYPE               ATRIBUTE 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          Last change: 12 Jul 2006                    2