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RE: Combinator library gets software prize
by Conal Elliott 23 Jan '01

23 Jan '01

> From: C.Reinke [mailto:C.Reinke@ukc.ac.uk] > Am I the only one who finds the exclusive emphasis on combinator > languages slightly disappointing [...]? > [...] > The paper somewhat downplays the role of embedding the > combinator-based DSL in a full functional language while also > mentioning that some features gained for free in the Haskell > prototype considerably complicate implementations in other > languages. I would be interested to hear more about these aspects: > [...] Another important consideration is whether the combinator library is higher-order. If so, it will be awkward to use from a language without a lightweight notation for (first-class) functions. This lack was a huge drawback in DirectAnimation, the now-defunct product cousin of Fran, which eviscerated the crucially higher-order event algebra. Similarly, when a combinator lib uses parametric polymorphism, it is painful to use from a language without. (Same example.) It seems that these features just weren't important in the case of "Composing Contracts". - Conal

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Doing IO in foldr repeats lines?
by Ian Lynagh 23 Jan '01

23 Jan '01

Hi all The following code: > module Main (main) where > import IO > main :: IO() > main = do _ <- foldl foo (return 14) ["qq\n", "ww\n", "ee\n"] > putStr "" > foo :: IO Int -> String -> IO Int > foo io_l s = do l <- io_l > () <- putStr s > io_l prints (with both GHC and hugs): qq ww qq ee qq ww qq and I really don't understand why. Is the code re-evaluated every time foldl is expanded or something? Thanks Ian, confused

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by Onwall.net 22 Jan '01

22 Jan '01

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Re: Combinator library gets software prize
by C.Reinke 22 Jan '01

22 Jan '01

> > This article is very good, and having read the conference paper earlier > > in the year I finished it with only one question: What's a 'quant' ... > > and is it good or bad to be one? > > > > "Ten years ago, Jean-Marc Eber, then a quant at Société > > Générale, ..." > > The OED has: .. > So perhaps he was tall, thin and fond of wearing a cap? > > :-) You might want to try http://www.dictionary.com/cgi-bin/dict.pl?term=quant An expert in the use of mathematics and related subjects, particularly in investment management and stock trading. ... http://www.investorwords.com/q1.htm#quant One who performs quantitative analyses. Or more generally, a securities analyst. Am I the only one who finds the exclusive emphasis on combinator languages slightly disappointing (in fact, the article seems to equate functional language with domain-specific combinator languages, which is more than a bit mistleading)? This is a Haskell forum, not one on Backus' FP, so readers are well aware of the advantages of functional abstraction. Domain-specific languages, if embedded in Haskell, tend to inherit these advantages, even if the language in question was designed as a pure combinator language. The consequence (and the intention, as far as one can gather from the paper) of the limitation to combinators is that this language can and will be used mainly in non-functional languages, not inheriting all that much from a functional style of programming. The same will probably hold for any communication standards based on it. This appplication is undoubtely a success and a good step forward, but there is more to functional languages. The paper somewhat downplays the role of embedding the combinator-based DSL in a full functional language while also mentioning that some features gained for free in the Haskell prototype considerably complicate implementations in other languages. I would be interested to hear more about these aspects: - Is the strictly combinator-based approach a pragmatic necessity ("one step at a time") or is there no need for more advanced features (especially abstraction) in the application area? - Has there been a comparison of the way the combinators of the DSL are used in Haskell and in other implementations? I would think that the use of abstraction to define more complex instruments in terms of the basic combinators should play a rather dominant role. On the other hand, I can imagine that users would want to have each complex instrument explicitly named and studied, instead of trusting large amounts of money to anonymous abstractions created on-the-fly. - What about interactive exploration of new instruments, e.g., in a Hugs or OCaml session (as opposed to changing a C++ implementation, or a stand-alone executable generated by an OCaml compiler, for every experiment)? Claus

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fixity for (\\)
by Koen Claessen 22 Jan '01

22 Jan '01

Hi all, The Haskell report defines the fixity of (\\) to be: infix 5 \\ I propose that it gets the following fixity: infixl 5 \\ This means that one can write: as \\ bs \\ cs \\ ds Which means: (((as \\ bs) \\ cs) \\ ds) I think that one less often means the following: as \\ (bs \\ (cs \\ ds)) /Koen. -- Koen Claessen http://www.cs.chalmers.se/~koen phone:+46-31-772 5424 mailto:koen@cs.chalmers.se ----------------------------------------------------- Chalmers University of Technology, Gothenburg, Sweden

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RE: Combinator library gets software prize
by David Bakin 22 Jan '01

22 Jan '01

This article is very good, and having read the conference paper earlier in the year I finished it with only one question: What's a 'quant' ... and is it good or bad to be one? "Ten years ago, Jean-Marc Eber, then a quant at Société Générale, ..." -- Dave -----Original Message----- From: Simon Peyton-Jones Sent: Saturday, January 20, 2001 5:10 AM To: haskell(a)haskell.org Subject: Combinator library gets software prize You might enjoy this article, in Risk Magazine, a journal of the financial engineering industry. Combinators in the real world! http://www.risk.net/riskawards2001/softwareproduct.htm <http://www.risk.net/riskawards2001/softwareproduct.htm> Simon _______________________________________________ Haskell mailing list Haskell(a)haskell.org http://www.haskell.org/mailman/listinfo/haskell <http://www.haskell.org/mailman/listinfo/haskell>

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RE: Combinator library gets software prize
by Ashley Yakeley 21 Jan '01

21 Jan '01

At 2001-01-21 10:57, David Bakin wrote: >What's a 'quant' ... >and is it good or bad to be one? I think that depends on exactly how much of a quant you are. -- Ashley Yakeley, Seattle WA

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Re: Combinator library gets software prize
by Laurent Guerby 21 Jan '01

21 Jan '01

I don't know if Simon mentionned it but I found his & al. paper proceedings of the fifth ACM SIGPLAN international conference on on Functional programming, "Composing contracts: an adventure in financial engineering (functional pearl) Pages 280-292" very interesting: http://www.acm.org/pubs/citations/proceedings/fp/351240/p280-jones/ -- Laurent Guerby <guerby(a)acm.org>

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Combinator library gets software prize
by Simon Peyton-Jones 20 Jan '01

20 Jan '01

You might enjoy this article, in Risk Magazine, a journal of the financial engineering industry. Combinators in the real world! http://www.risk.net/riskawards2001/softwareproduct.htm Simon

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Student Cheating?
by F. Warren Burton 19 Jan '01

19 Jan '01

How many readers of this list got a copy of the following? Did somebody reading this list assign this problem? Warren >X-Originating-IP: [194.83.240.16] >From: "Rachael Maguire" <rachael_maguire(a)hotmail.com> >To: burton(a)cs.sfu.ca >Subject: haskell programming problem >Date: Thu, 18 Jan 2001 21:21:25 -0000 >X-OriginalArrivalTime: 18 Jan 2001 21:21:25.0578 (UTC) >FILETIME=[9D03AAA0:01C08194] > >I come across your e-mail address via the haskell.org website. I am >having some difficulty with the language and am wondering if you can >help due to your programming experience in Haskell. Could you write >me a small program to count the number of words and characters from >a string (the strings contents would be specified in the script >containing the Haskell code for this mall program). Also the program >must justify the string. Could you send me some code for a program >of this kind as I do not know any people with experience of Haskell >programming . > >Any help would be much appreciated. >Thanks in advance Rachael. >_________________________________________________________________________ >Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com.

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