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From: jlg@cochiti.lanl.gov (Jim Giles)
Newsgroups: comp.lang.fortran
Subject: Re: Standards
Keywords: Fortran 90 standards
Message-ID: <23170@lanl.gov>
Date: 3 May 91 20:50:37 GMT
References: <12528@exodus.Eng.Sun.COM> <22913@lanl.gov> <21649@paperboy.OSF.ORG>
Sender: news@lanl.gov
Organization: Los Alamos National Laboratory
Lines: 29

In article <21649@paperboy.OSF.ORG>, andyj@osf.org (Andy Johnson) writes:
|> In article <22913@lanl.gov>, jlg@cochiti.lanl.gov (Jim Giles) writes:
|> [...]
|> |> Well, I am not aware of _any_ language or _any_ implementation of
|> |> any language which has "pointers" implemented in the undesireable
|> |> manner that the Fortran 90 proposal defines.  It is _not_ existing
|> |> practice.  Independent of that, it is simply not a good design.
|> 
|> Sure you are, it's called FORTRAN.  The model that is used for POINTERs is
|> exactly analogous to the existing pointers in most Fortran implementations:
|> dummy arguments.

My objection to pointers is founded on the fact that they inhibit
optimization and conceal errors in the presence of assignment to any 
of the aliased objects.  Since Fortran parameter passing _prohibits_
such aliasing, your claim that they resemble pointers is false in 
exactly that part of the semantics I object to.  The Fortran 90
proposal includes pointers to array slices, which will cause aliasing
(and inhibit optimizations) on all arrays to which they are applied.
This will occur even though pointers to array slices provide _no_
additional functionality!  They could have been left out entirely
without effecting the capabilities of the language at all.  Pointers
to scalars are useful in implementing recursive data structures.
Although I would rather the committee support recursive data types
directly, I have no strong objection to pointer being used in this 
way.  Pointers to arrays don't do anything useful, they just inhibit
optimization and generate debugging problems.

J. Giles