signed zeros

[Steve Kargl]

On Thu, Jul 29, 2010 at 08:15:43PM -0400, Jack Howarth wrote:
> On Thu, Jul 29, 2010 at 05:11:48PM -0700, Steve Kargl wrote:
> > On Thu, Jul 29, 2010 at 08:04:22PM -0400, Jack Howarth wrote:
> > > 
> > > Steve,
> > >     Well the current behavior is rather silly. It assumes
> > > that the user should be told that a value truncated in
> > > output is a non-zero negative value whereas it is silent
> > > on the case of positive numbers that are non-zero. If one
> > > is going to this extreme with i/o, the compiler should be
> > > emitting...
> > > 
> > > -0.0000 for values less than zero
> > >  0.0000 for zero itself
> > > +0.0000 for values greater than zero
> > > 
> > > Otherwise we should at least try to find another fortran
> > > compiler than supports this weird behavior.
> > >                Jack
> > 
> > Apparently, you have had no formal training in real analysis
> > where -0 is an important entity.  Note, the standard explicitly
> > states a leading + sign can be omitted.  You can force the plus
> > sign if you like:
> > 
> > troutmask:kargl[207] cat a.f90
> >       STEPCH=0.2511847893E-05
> >       WRITE(6,'(A,SP,F10.4)') ' ------ stepsize=',STEPCH
> >       END
> > troutmask:kargl[208] ~/../sgk/work/4x/bin/gfortran -o z a.f90 && ./z
> >  ------ stepsize=   +0.0000
> > 
> 
> Steve,
>    Again, point me to another fortran compiler with this
> behavior. Ruthlessly strict interpretations of the standard
> which creates a compiler with unconventional behavior is
> of limited use. Especially when running testsuites which
> must compare the logged output for more than just gfortran
> builds of the software.
>            Jack
> 

Just use the -fno-sign-zero option.

PS: I don't care what other compilers do.

PPS:  Here's another option if you want +0.

troutmask:kargl[210] cat a.f90
      STEPCH=0.2511847893E-05
      open(unit=6,sign='plus')
      WRITE(6,'(A,F10.4)') ' ------ stepsize=',STEPCH
      END
troutmask:kargl[211] ~/../sgk/work/4x/bin/gfortran -o z a.f90 && ./z
 ------ stepsize=   +0.0000


-- 
Steve