[Haskell-cafe] Is Haskell a 5GL?
Robert Dockins
robdockins at fastmail.fm
Fri Sep 29 11:00:45 EDT 2006
On Sep 28, 2006, at 8:47 PM, David Curran wrote:
> Sorry if this comes across as the rant it is. If you are interested in
> doing useful stuff rather then navel gazing please stop here.
>
> Where are compute languages going?
> I think multi core, distributed, fault tolerant.
> So you would end up with a computer of the sort envisioned by Hillis
> in the 80s with his data parallel programs. The only language that
> seems even close to this model is Erlang. What am I missing about the
> ability of Haskell to distribute across processors or a network?
>
> Say instead of fault tolerant it is fault avoiding.
> Can proving programs correct (with Haskell) really reduce our
> workload?
> http://www.seas.upenn.edu/~sweirich/wmm/03-benton.pdf
I read that paper as saying formal methods have an extremely steep
learning curve and large initial investment, but that the learning
and initial investment pay off over time. The author found that,
even in the short time he worked with it, formal methods saved time
when he needed to modify his definitions (third paragraph in the
second column). As with many automation tasks, the payoff comes with
repeated identical or similar iterations. Furthermore, his acquired
knowledge transferred well to an unrelated project. I can personally
vouch for many of his experiences, having worked some with Coq myself.
> Finally is Haskell a language for programming or a mental gymnasium
> that might be the proving ground for concepts in the next popular
> language? To quote from a post on the topic "Old functional
> programming ideas " on programming.reddit.com
I don't know how much you agree with this quote, but for the purposes
of discussion I'll assume that you have expressed these views
personally. You did, after all, preface your message by saying it
was a rant so I'm going to assume you're prepared for the flames. ;-)
> "Church-Turing equivalence tells us that all models of recursive
> computing have the same formal power. But it tells us nothing about
> which models are the most effective way for humans to understand and
> express definitions of functions. For some reason I'd expect
> researchers in programming languages to have a lot of opinions on this
> subject. But they don't seem to talk about it much.
I think the Haskell community is doing better than many in this
regard. There is a concurrent thread on haskell-prime occurring
_right now_ about whether pattern guards should be in Haskell'. The
primary point of disagreement is about whether pattern guards are a
more effective way for humans to understand and express definitions
of functions or not! The ages-old disagreement about top-level state
is similar, if more heated. Similar for (n+k) patterns, and a host
of other issues. The endless discussions about monads often revolve
around the goal of achieving new and better ways to express
complicated function definitions.
I think this is because a fundamental value of the Haskell community
is flexibility of the language. Many languages are presented to the
programmer as a complete package, which doesn't encourage them to
consider the various possible design decisions that went into
creating that language. With Haskell, new users are often quickly
confronted with various different ways of expressing their goals and
with extensions they can enable (or not) and are forced to consider
how best to express their program. I think this is more good than it
is bad.
> Instead, a cynical and mean-spirited person might come to the
> conclusion that PL researchers (such as Wadler) are actually just
> mathematicians,
You seem to say this like its a bad thing; I completely disagree. I
don't think of myself as mean-spirited, and I have no problems
calling, eg, Wadler a mathematician. Just as I would call Church and
Turing and Kleene and Goedel and Milner (etc, etc, etc)
mathematicians. If someone were ever to call _me_ a mathematician, I
would consider it an honor. Furthermore, if anyone attempted to
belittle these distinguished persons or their accomplishments by
calling them "just" mathematicians, I would begin to question his or
her qualifications to have an opinion on the subject worthy of
consideration.
The field mathematics has a long and glorious history of helping
people to solve real problems. I don't understand this undercurrent
of antagonism that some people in our field have towards it. Let's
be honest: developing correct programs that perform non-trivial tasks
and reasoning about them is HARD. The techniques of mathematics and
its sister discipline formal logic can help us with these tasks. I
find it a little strange that this position even requires a defense.
All of the other scientific and engineering disciplines embrace the
mathematics that help them do their work. I don't believe there are
very many physicists who would call Newton a mathematician and intend
it to be a derogatory term.
I personally see some of the primary goals of PL research as 1) to
explore new ideas in PLs (obviously) and 2) to try to close the gap
between the mathematics underlying computation and the realities of
programming in the trenches. I think Haskell has spurred great
advances toward both of these goals, and has come closer to achieving
the second than any other language I know of (with the possible
exception of SML, but *grumble* side-effects *grumble*, etc)
> who happen to have discovered a new name for their
> specialty which comes with a lot more funding. They certainly seem
> quite comfortable working in a notation that almost no programmers
> understand or seem to be learning.
Call me elitist if you want, but I don't want anyone who refuses or
is unable to learn calculus to be, eg, a civil engineer. He don't
have to be an expert in real analysis, but if he don't understand the
basics, I don't want him building any bridges that I'm going to be
driving on!
In a similar way, if a someone refuses or is unable to learn the
mathematical foundations of computation, I don't think I really want
him programming any systems that I'm going to be relying on. He
don't need to be an expert in category theory, but if programmers
aren't learning the skills they need to understand the basics and
mathematical notation of PL theory, then something is very, very
wrong. (Not to beat you over the head with my point, but what I'm
saying is that programmers really ought to know this stuff and the
fact that most do not is a terrible state of affairs).
> If a responsible scientist wanted to counter this cynical,
> mean-spirited, and generally Luddite and Philistine argument, what
> would he or she say?"
Mu
Rob Dockins
Speak softly and drive a Sherman tank.
Laugh hard; it's a long way to the bank.
-- TMBG
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