Path: utzoo!utgpu!water!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!mailrus!nrl-cmf!cmcl2!lanl!jlg
From: jlg@lanl.gov (Jim Giles)
Newsgroups: comp.lang.fortran
Subject: Re: Fortran versus C for numerical anal
Message-ID: <3708@lanl.gov>
Date: 17 Sep 88 00:48:01 GMT
References: <50500075@uxe.cso.uiuc.edu>
Organization: Los Alamos National Laboratory
Lines: 41

From article <50500075@uxe.cso.uiuc.edu>, by mcdonald@uxe.cso.uiuc.edu:
>> 	(*twodarray)[10][5] = 'c';
> [... long example showing code generated ...]
> 
> Sure looks like array indexing calculations to me. [...]

Still doesn't look like array indexing to me.  Now _if_ the parenthesis
and asterisk could be removed - then you'd have something.  The fact is,
the semantics _and_ the syntax should be the same for dynamic and static 
arrays - the only difference should be a 'dynamic' flag on the declaration
and an allocation call.  All you've shown me here is an example of the 
weakness that I've objected to all along - the same semantics but two 
incompatible syntaxes.  This goes along with other dynamic array mechanisms 
which allow the same syntax but have different semantics.  I hope that when
Fortran includes a dynamic array capability it will fit more elegantly
into the language than C's capability does.

Consider the Fortran 8x proposal for allocatable arrays:

      REAL, ALLOCATABLE :: twodarray (:,:)

      ...

      ALLOCATE (twodarray(5,10))

      ...

      twodarray(5,10) = 5.0

      ...

Note that a _use_ of the 2-d array looks just like the use of any other
2-d array - static or dynamic.  The semantics are also identical except
that the address of 'twodarray' doesn't become defined until run-time
(neither does the size).  Any optimization that Fortran could apply
to a statically allocated array with unknown extent (like an argument to
a function, for example) can be applied to this one in _exactly_ the 
same way.

J. Giles
Los Alamos