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Humanist Archives: June 3, 2020, 9:18 a.m. Humanist 34.78 - hardware architecture and programming style

                  Humanist Discussion Group, Vol. 34, No. 78.
            Department of Digital Humanities, King's College London
                   Hosted by King's Digital Lab
                Submit to: humanist@dhhumanist.org

        Date: 2020-06-02 18:15:11+00:00
        From: Tim Smithers 
        Subject: Re: [Humanist] 34.76: hardware architecture and programming style?

Dear Willard,

So you've been looking at Robert Sebestra's massive tome.

Despite the more than 1300 pages of this (in the 2019 12th
Edition I looked at), I wouldn't call what Sebestra does as
"makes a case that ..."  Rather, I'd call it a superficial and
unconvincing hand-wave.  For a much better job I would point
you to the Backus paper, Sebestra cites.

    John Backus, 1978.  Can Programming Be Liberated from the
    von Neumann Style?  A Functional Style and Its Algebra of
    Programs, Communications of the ACM, Vol 21, No 8, pp

You may have looked at this too, but in case not, I'd like to
divert you to this.  It's a long paper, some 29 pages, and
very detailed, but Backus helpfully included a nice summary at
the end in Section 16, page 639.

This seems to be a somewhat neglected paper, perhaps due to
its length and detail, but I think it contains much important
analysis of the von Neumann architecture, and what it can do
well, and not do well, as well as important ideas for what it
would take to have something different, and thus, in Backus'
view, better programming languages.

This neglect may have more to do with Moore's law, and the
massive increase in computational power and capacity of real
von Neumann machines since 1978, so much so that we now build
virtual computers on these von Neumann machines having
different architectures, and not notice any slowness or
significant loss of performance.  Of course, these virtual
machines don't change the von Machine underneath them, but
they do allows us to completely forget about it, and thus,
returning to the Backus question, liberate our programming
from the von Neumann style.  Liberation has been won by
building up and away from the von Neumann basement, and not by
moving to a new basement, as John Backus envisaged we would
need to do, is how I see what's happened.

Best regards,


> On 02 Jun 2020, at 12:53, Humanist  wrote:
>                  Humanist Discussion Group, Vol. 34, No. 76.
>            Department of Digital Humanities, King's College London
>                   Hosted by King's Digital Lab
>                       www.dhhumanist.org
>                Submit to: humanist@dhhumanist.org
>        Date: 2020-06-01 09:26:47+00:00
>        From: Willard McCarty 
>        Subject: hardware architecture and programming style
> Robert Sebestra, in Concepts of Programming Languages (11th edn, 2016),
> makes the case that the imperative style of programming characteristic
> of most languages now in use is more or less determined by the so-called
> von Neumann architecture of hardware common to our machines. Other styles,
> notably the functional one pioneered by McCarthy in Lisp, can be
> accommodated by translating them via a compiler or interpreter into
> imperative code. A number of early comparisons of software with
> mathematics draw the distinction based on the outgrown characterisation
> of the former as imperative, noting that the latter is descriptive.
> Still there's the von Neumann structure to keep the distinction alive.
> Promises of other architectures are not difficult to find. Is it reasonable
> to expect a very different relationship between software and mathematics
> that would result if these alternative architectures were widely available?
> Those here who know what I am talking about must be able to spot the
> muddle I'd very much like to find a way out of. Is clear guidance to be
> had? As with any issue involving up-to-the-minute technological
> progress, the swarm of promises makes getting out of muddles difficult.
> All help appreciated, esp if it comes as reference to credible publications.
> Many thanks.
> Yours,
> WM
> --
> Willard McCarty (www.mccarty.org.uk/),
> Professor emeritus, Department of Digital Humanities, King's College
> London; Editor, Interdisciplinary Science Reviews
> (www.tandfonline.com/loi/yisr20) and Humanist (www.dhhumanist.org)

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