Re: It Hurts When I Do This

Beliavsky <beliavsky@[EMAIL PROTECTED]
> wrote:

> The blog entry mentions a problem that combines allocation upon
> assignment (new in Fortran 2003) and array sections. Although some
> compilers now sup****t a line of code
> 
> A = B
> 
> where A is declared ALLOCATABLE and is here allocated to the shape of
> B and then assigned to it, I am wary of using this feature, because
> assignments in Fortran, up to now, have been separated from
> allocations (unless I am mistaken),

Depends what you mean by "up to now". That particular variant of
allocate-on-assignment is new to f2003. But allocation of allocatable
components on assignment is an integral part of the allocatable TR.
Allocatable components pretty much don't work without that. Admitedly,
the alocatable TR isn't exactly very old.

The fact that there was already such allocation for components was one
of the arguments for adding the feature to objects that weren't
components. It seemed inconsistent to have automatic reallocation for
one, but not the other. It also seemed like it would invite people to
add the superfluous complication of putting things in a derived type
just to get the automatic allocation.

> I wonder what people think of this style suggestion.

I repeat my unanswered question to... (I forget who; someone else in
this thread): what about allocatable strings? It has been my observation
that the rather large majority of people intuitively expect strings to
act like the new allocatable ones will. They expect that

  string = 'hello'

will end up with string being 4 characters in length. They have to be
carefully trained to understand how Fortran fixed-length strings work.

I expect allocatable strings to eventually become almost the norm, with
fixed-length strings reserved for special cases.

So I wonder whether you would also extend your style choice to
allocatable strings. I personally think that the automatic reallocation
is more intuitive than the current scheme, which is (a bit
inconsistently)

1. For strings, pad or truncate to make things work. It is never an
error.

2. For arrays, if the size wasn't pre-allocated just right, it is an
error.

I think it is much more natural that, if someone writes

  X = something

then they probably want X to end up having the same size or length as
the something. I think that the resistance to this reflects being
trained in prior Fortran practice, as distinguished from ab initio
reevaluations of natural useability. Alternatively, maybe it's just that
my intuition is different.

-- 
Richard Maine                    | Good judgement comes from experience;
email: last name at domain . net | experience comes from bad judgement.
domain: summertriangle           |  -- Mark Twain