Mathematical Library Functions                          log1p(3M)



NAME
     log1p, log1pf, log1pl - compute natural logarithm

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

     double log1p(double x);


     float log1pf(float x);


     long double log1pl(long double x);


DESCRIPTION
     These functions compute log(e)(1.0 ] x).

RETURN VALUES
     Upon  successful  completion,  these  functions  return  the
     natural logarithm of 1.0 ] x.


     If x is -1, a pole error occurs and log1p(),  log1pf(),  and
     log1pl()   return  -HUGEVAL,  -HUGEVALF,  and  -HUGEVAL,
     respectively.


     For finite values of x that are less than -1,  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 ]0 or ]Inf, x is returned.


     For exceptional cases, matherr(3M) tabulates the  values  to
     be returned by log1p() as specified by SVID3 and XPG3.

ERORS
     These functions will fail if:

     Domain Error    The finite value of x is less than -1, or  x
                     is -Inf.

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




SunOS 5.11          Last change: 12 Jul 2006                    1






Mathematical Library Functions                          log1p(3M)



                     The log1p() function sets errno to  EDOM  if
                     the value of x is less than -1.


     Pole Error      The value of x is -1.

                     If the integer expression  (matherrhandling
                     &  MATHEREXCEPT)  is non-zero, 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.


     An application can  also  set  errno  to  0  before  calling
     log1p().  On  return,  if  errno  is  non-zero, an error has
     occurred. The log1pf() and log1pl()  functions  do  not  set
     errno.

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











SunOS 5.11          Last change: 12 Jul 2006                    2