Standard C Library Functions                       fpgetround(3C)



NAME
     fpgetround, fpsetround, fpgetmask,  fpsetmask,  fpgetsticky,
     fpsetsticky - IE floating-point environment control

SYNOPSIS
     #include 

     fprnd fpgetround(void);


     fprnd fpsetround(fprnd rnddir);


     fpexcept fpgetmask(void);


     fpexcept fpsetmask(fpexcept mask);


     fpexcept fpgetsticky(void);


     fpexcept fpsetsticky(fpexcept sticky);


DESCRIPTION
     There are five floating-point exceptions:

         o    divide-by-zero,

         o    overflow,

         o    underflow,

         o    imprecise (inexact) result, and

         o    invalid operation.


     When a floating-point exception  occurs,  the  corresponding
     sticky  bit  is set (1), and if the mask bit is enabled (1),
     the trap takes place. These routines let the user change the
     behavior  on  occurrence of any of these exceptions, as well
     as change the rounding mode for floating-point operations.


     The mask argument is formed by the logical OR  operation  of
     the following floating-point exception masks:

       FPXINV       /* invalid operation exception */
       FPXOFL       /* overflow exception */
       FPXUFL       /* underflow exception */



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Standard C Library Functions                       fpgetround(3C)



       FPXDZ        /* divide-by-zero exception */
       FPXIMP       /* imprecise (loss of precision) */



     The following floating-point rounding modes  are  passed  to
     fpsetround and returned by  fpgetround().

       FPRN       /* round to nearest representative number */
       FPRP       /* round to plus infinity */
       FPRM       /* round to minus infinity */
       FPRZ       /* round to zero (truncate) */



     The default environment is  rounding  mode  set  to  nearest
     (FPRN) and all traps disabled.


     The fpsetsticky() function modifies all  sticky  flags.  The
     fpsetmask()  function changes all mask bits. The fpsetmask()
     function clears the sticky bit corresponding to  any  excep-
     tion being enabled.

RETURN VALUES
     The fpgetround() function returns the current rounding mode.


     The fpsetround() function sets the rounding mode and returns
     the previous rounding mode.


     The  fpgetmask()  function  returns  the  current  exception
     masks.


     The  fpsetmask()  function  sets  the  exception  masks  and
     returns the previous setting.


     The fpgetsticky() function  returns  the  current  exception
     sticky flags.


     The  fpsetsticky()  function  sets  (clears)  the  exception
     sticky flags and  returns the previous setting.

USAGE
     The C programming language  requires  truncation  (round  to
     zero)  for  floating  point  to  integral  conversions.  The
     current rounding mode has no effect on these conversions.




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Standard C Library Functions                       fpgetround(3C)



     The sticky bit must be cleared to recover from the trap  and
     proceed.   If  the sticky bit is not cleared before the next
     trap occurs, a wrong exception type may be signaled.


     Individual bits may be examined using the constants  defined
     in .

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



     
           ATRIBUTE TYPE               ATRIBUTE VALUE       
    
     MT-Level                     MT-Safe                     
    


SEE ALSO
     isnand(3C), attributes(5)
































SunOS 5.11          Last change: 29 Dec 1996                    3