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NAME
     ieee_flags - mode and  status  function  for  IEEE  standard
     arithmetic

SYNOPSIS
     cc [ flag ... ] file ...  -lsunmath -lm [ library ... ]

     #include <sunmath.h>

     int ieee_flags(const char *action, const char  *mode,  const
     char *in, char **out);

DESCRIPTION
     This function provides easy access to the modes  and  status
     required  to fully exploit ANSI/IEEE Std 754-1985 arithmetic
     in a C program.  All  arguments  are  pointers  to  strings.
     Results  arising from invalid arguments and invalid combina-
     tions are undefined for efficiency.

     There  are  four  types  of   action:    ``get'',   ``set'',
     ``clear'', and ``clearall''.  There are three valid settings
     for mode, two corresponding to modes of IEEE arithmetic:


          ``direction'',      ... current rounding direction mode
          ``precision'',      ... current rounding precision mode

     and one corresponding to status of IEEE arithmetic:


          ``exception''.           ... accrued exception-occurred status

     There are 14 types of in and out :


          ``nearest'',        ... round toward nearest
          ``tozero'',         ... round toward zero
          ``negative'',       ... round toward negative infinity
          ``positive'',       ... round toward positive infinity
          ``extended'',
          ``double'',
          ``single'',
          ``inexact'',
          ``division'',       ... division by zero exception
          ``underflow'',
          ``overflow'',
          ``invalid'',
          ``all'',            ... all five exceptions above
          ``common''.         ... invalid, overflow, and division exceptions

     Note: ``all'' and ``common'' only make sense with ``set'' or
     ``clear''.
     For ``clearall'', ieee_flags() returns 0  and  restores  all
     default  modes and status.  Nothing will be assigned to out.
     Thus


          char *mode, *out, *in;
          ieee_flags("clearall",mode, in, &out);

     set rounding direction to ``nearest'', rounding precision to
     ``extended'',  and  all accrued exception-occurred status to
     zero.

     For ``clear'',  ieee_flags()  returns  0  and  restores  the
     default  mode  or  status.  Nothing will be assigned to out.
     Thus


          char *out, *in;
          ieee_flags("clear","direction", in, &out);       ... set rounding direction to round to nearest.

     For ``set'', ieee_flags() returns 0 if the  action  is  suc-
     cessful  and  1 if the corresponding required status or mode
     is not available (for instance, not supported in  hardware).
     Nothing will be assigned to out.  Thus


          char *out, *in;
          ieee_flags ("set","direction","tozero",&out);     ... set rounding direction to round toward zero;

     For ``get'', we have the following cases:

     Case 1:  mode is ``direction''. In that  case,  out  returns
     one  of  the  four  strings ``nearest'', ``tozero'', ``posi-
     tive'',  ``negative'';  and  ieee_flags()  returns  a  value
     corresponding to out according to the enum fp_direction_type
     defined in <sys/ieeefp.h>.

     Case 2:  mode is ``precision''. In that  case,  out  returns
     one  of  the  three strings ``extended'', ``double'', ``sin-
     gle''; and ieee_flags() returns a value corresponding to out
     according   to   the   enum   fp_precision_type  defined  in
     <sys/ieeefp.h>.

     Case 3:  mode is ``exception''. In that case, out returns


          (a) ``not available'' if information on exception is not available,
          (b) ``'' (the empty string) if no accrued exception,
          (c) the accrued exception that has the highest priority according to the list below

               (1) the exception named by in,
               (2) ``invalid'',
               (3) ``overflow'',
               (4) ``division'',
               (5) ``underflow'',
               (6) ``inexact''.

     In this case ieee_flags() returns a five or  six  bit  value
     where    each    bit    (cf.   enum   fp_exception_type   in
     <sys/ieeefp.h>) corresponds to an exception-occurred accrued
     status  flag:  0  = off, 1 = on.  The bit corresponding to a
     particular  exception  varies   among   architectures;   see
     /usr/include/sys/ieeefp.h.

     Example:


          extern int ieee_flags(const char *, const char *, const char *, char **);
          char *out;
          int k;
          ieee_flags ("clear","exception","all",&out); /* clear all accrued exceptions */
          ...
          ... (code that generates three exceptions: overflow, invalid, inexact)
          ...
          k = ieee_flags("get","exception","overflow",&out);

     then out = ``overflow'', and  k=25.

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