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From: jlg@lanl.gov (Jim Giles)
Newsgroups: comp.lang.fortran
Subject: Re: Education for Fortran 90 (was: Fortran 9X replaced by Ada 9X ?)
Message-ID: <63470@lanl.gov>
Date: 19 Sep 90 21:14:46 GMT
References: <142733@sun.Eng.Sun.COM>
Organization: Los Alamos Natl Lab, Los Alamos, N.M.
Lines: 32

From article <142733@sun.Eng.Sun.COM>, by wsb@boise.Eng.Sun.COM (Walt Brainerd):
> [...]
> Regarding pointers, the kind J. Giles wants (addresses) were not
> put in Fortran 90.  By a narrow margin, the X3J3 folks preferred
> "descriptors" or "aliases" as the model.  Hence one of these things
> (call them what you like) can "point to" / "alias" / "reference"
> a row or a column of an array (or a two-dimensional part or
> a five-dimensional array, or the next element in a linked list,
> etc.).  Obviously this is useful, even if it is not what
> J. Giles wants (and we should have some examples in the book
> of pointers to sections of an array!).

Actually, this is what I object to - the casual assertion that "Obviously
this is useful."  It does not give the user any functionality that he
doesn't have with array subscript expressions already.  What it does
is introduce the spectre of aliasing unnecessarily.  The committee tried
to allay such fears with the "TARGET" attribute, but any two pointers
of the same type are still assumed to be aliased - even if they always
point into different arrays.  In order to avoid this problem, the user
will have to use array subscript expressions directly instead of pointing
to the section - but this is what the user would have to do even if the
pointer-to-section feature didn't exist. So the feature doesn't add
anything new.  It just adds a "syntactic sugar" notation that users will
have to be taught to avoid.  The use of pointers should be limited to
simulating recursive data structures and the pointer-to-section idea
should be deleted from the standard.

Now, if they wanted to reintroduce the "ALIAS/IDENTIFY" feature - which
really _does_ add functionality - then there would be reason to consider
the proposal more seriously.

J. Giles