Richard Maine wrote:
>
> [log in to unmask] writes:
> > Michael Metcalf writes:
> > > Message text written by Lars Mossberg
> > > >After all, Fortran DOES support zero-sized objects and they DO exist and
> > > ARE defined and
> > > "a" and "b" DO point to the same target, or?<
> > >
> > > Agreed. But the standard says, in the definition of ASSOCIATED, that for
> > > zero-size arrays the result is false.
> > >
> >
> > This seems like an unfortunate choice. I often test pointer
> > association status before deallocation....
>
> Different issue. You are talking about the one-argument form of
> associated, which asks whether a pointer is associated with anything.
> That form works as you'd expect...Well, there are the issues of
> undefined association status, which may not be something you'd
> expect. But there is nothing special about zero size for that
> form.
>
> The special case for zero-sized arrays applies only to the
> two-argument form of associated, which asks whether two pointers
> are associated *WITH THE SAME THING* (or whether a pointer is
> associated with a particular target).
>
> The standard says that two zero-sized pointers are never associated
> with the same thing (since they have no elements in common). They
> may still both be associated - just not with the same thing.
>
> I do happen to think that the standard's choice is, as you say,
> unfortunate. But at least its a less common situation.
Yeah, it's an unfortunate choice. Unfortunately, there are no
fortunate choices. Suppose P1 and P2 are pointers, what should happen
to ASSOCIATED(P1,P2) for
P1 => array(10:9) ; P2 => array(10:8)
or
P1 => array(10:9) ; P2 => array(5:4)
or
P1 => array(1:2:-1); P2 => array(2:1)
or
P1 => array(2:1) ; P2 => other_array(2:1)
or suppose "other_array" is actually a pointer and points to array.
The list of dumb things people can do with zero sized arrays is
unfortunately non-zero sized.
For what it's worth, I don't like the choice either. In fact at
one X3J3 meeting I had a paper that "proved" TRUE was the best
result as the size of the arrays approached zero.
Dick Hendrickson
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