Re: RFA: Revamp fortran array types

["N.M. Maclaren" <nmm1 at cam dot ac dot uk>]

On Aug 20 2009, Paolo Bonzini wrote:
> On 08/19/2009 07:59 PM, Toon Moene wrote:
> > Steve Kargl wrote:
> > > On Wed, Aug 19, 2009 at 06:43:13PM +0200, Toon Moene wrote:
> >
> > > > The following code is perfectly OK:
> > > >
> > > > DIMENSION A(10)
> > > > A = 10.0
> > > > CALL SUB(A,A)
> > > > END
> > > > SUBROUTINE SUB(A,B)
> > > > REAL, INTENT(IN) :: A(:), B(:)
> > >
> > > What happens if you replace the last line with
> > >
> > > REAL, INTENT(IN) :: A(:)
> > > REAL, INTENT(OUT) :: B(:)
> >
> > Fascinating. I *think* that - as long as you do not actually write to B
> > - you're in the clear.

Yes.  That's the origin of the ASYNCHRONOUS loophole in the standard that
I need to get fixed.

> I think even B(2) = A(1) would be fine.  Or even
>
>   B(2:N:2) = A(1:N-1:2)

Absolutely NOT!  That is permitted only for assumed size arrays (another
reason not to use them).  On the other hand, replacing the CALL by:

   CALL SUB(A(2:N:2),A(1:N-1:2))

would then allow B = A in SUB.


Regards,
Nick Maclaren.