Man Page f77_ieee_environment.3f

NAME

     f77_ieee_environment - mode, status, and signal handling for
     IEEE arithmetic

SYNOPSIS

     #include <f77/f77_floatingpoint.h>

     integer*4 function ieee_flags(action,mode,in,out)
     character*(*) action, mode, in, out

     integer*4 function ieee_handler(action,exception,hdl)
     character*(*) action, exception
     sigfpe_handler_type hdl

     sigfpe_handler_type function sigfpe(code, hdl)
     sigfpe_code_type code
     sigfpe_handler_type hdl

DESCRIPTION

     These subprograms provide modes and status required to fully
     exploit  ANSI/IEEE Standard 754-1985 arithmetic in a FORTRAN
     program.   They  correspond   closely   to   the   functions
     ieee_flags(3M), ieee_handler(3M), and sigfpe(3).

USAGE

     Example 1: Set rounding  direction  to  round  toward  zero,
     unless  the  hardware  does  not  support  directed rounding
     modes:

          integer*4 ieeer
          character*1 mode, out, in
          ieeer = ieee_flags('set', 'direction', 'tozero', out)

     Example 2: Clear rounding direction to default, round toward
     nearest:

          character*1 out, in
          ieeer = ieee_flags('clear','direction', in, out)

     Example 3: Clear all accrued exception-occurred bits:

          character*16 out
          ieeer = ieee_flags('clear','exception','all',out)

     Example 4: If example 3 generates  the  overflow  exception,
     detect the exception as follows:

          character*16 out
          ieeer = ieee_flags('get','exception','overflow', out)



     Example 5: A user-specified signal handler, with a main pro-
     gram to use it:

          external hand
          real r / 14.2 /,  s / 0.0 /
          i = ieee_handler( 'set', 'division', hand )
          t = r/s
          end

          integer function hand ( sig, sip, uap )
          integer sig, address
          structure /fault/
               integer address
          end structure

          structure /siginfo/
               integer si_signo
               integer si_code
               integer si_errno
               record /fault/ fault
          end structure

          record /siginfo/ sip

          address = sip.fault.address
          write (*,10) address
      10  format('Exception at hex address ', z8 )
          end

FILES

     include/f77/f77_floatingpoint.h
     libm.a

SEE ALSO

     floatingpoint(5),           signal(3c),           sigfpe(3),
     f77_floatingpoint(3F), ieee_flags(3M), ieee_handler(3M), and
     the Numerical Computation Guide