July 2002 - Haskell-Cafe

RE: can a lazy language give fast code?
by Simon Marlow 31 Jul '02

31 Jul '02

> Can one write withthe Haskell compliler faster code than in > the examples of http://www.bagley.org/~doug/shootout/ where > GHC (old Haskell 98?) seems to be much slower than Ocaml or > Mlton both strict functional languages. > Can one expect any improvements in speed in the future? Many of those programs can be written differently to improve performance. One issue that is affecting performance in several cases is the speed of character I/O, and the representation of Strings as lists of characters. Dramatic improvements can be had by using unboxed arrays of Char (Data.Array.Unboxed), or PackedString (which these days is implemented using unboxed arrays in GHC). Cheers, Simon

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can a lazy language give fast code?
by Scott J. 31 Jul '02

31 Jul '02

Hi, Can one write withthe Haskell compliler faster code than in the examples of http://www.bagley.org/~doug/shootout/ where GHC (old Haskell 98?) seems to be much slower than Ocaml or Mlton both strict functional languages. Can one expect any improvements in speed in the future? Cheers Scott

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Re: Infix expressions
by Yoann Padioleau 30 Jul '02

30 Jul '02

Ken Shan <ken(a)digitas.harvard.edu> writes: > --a8Wt8u1KmwUX3Y2C > Content-Type: text/plain; charset=us-ascii > Content-Disposition: inline > Content-Transfer-Encoding: quoted-printable > > Hello, > > In Haskell, backquotes can be used to convert individual identifiers > into infix operators, but not complex expressions. For example, > > [1,2,3] `zip` [4,5,6] > > is OK, but not > > [1,2,3] `zipWith (+)` [4,5,6] > > Is there any reason other than potential confusion when one of the two > backquotes is accidentally omitted? > > In any case, perhaps some people on this mailing list would appreciate > the following implementation of "infix expressions" that Dylan Thurston > and I came up with -- as algebraic and perverse as we could manage: > > infixr 0 -:, :- > data Infix f y =3D f :- y > x -:f:- y =3D x `f` y > > main =3D print $ [1,2,3] -: zipWith (+) :- [4,5,6] This is a funny tricks. Does some people know other kind of tricks (possibly in other functionnal langage) ? > > --=20 > Edit this signature at http://www.digitas.harvard.edu/cgi-bin/ken/sig > The trick is that there is no trick. > > --a8Wt8u1KmwUX3Y2C > Content-Type: application/pgp-signature > Content-Disposition: inline > > -----BEGIN PGP SIGNATURE----- > Version: GnuPG v1.0.7 (GNU/Linux) > > iD8DBQE9RZgzzjAc4f+uuBURAjl6AKCQmYb0HJvk2VicBlRD6zRX9VfRRgCg9F2B > YPXu07Uqrz8pj2iUt+HVM3U= > =WjJq > -----END PGP SIGNATURE----- > > --a8Wt8u1KmwUX3Y2C-- > _______________________________________________ > Haskell-Cafe mailing list > Haskell-Cafe(a)haskell.org > http://www.haskell.org/mailman/listinfo/haskell-cafe > -- Yoann Padioleau, INSA de Rennes, France, Opinions expressed here are only mine. Je n'écris qu'à titre personnel. **____ Get Free. Be Smart. Simply use Linux and Free Software. ____**

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Infix expressions
by Ken Shan 29 Jul '02

29 Jul '02

Hello, In Haskell, backquotes can be used to convert individual identifiers into infix operators, but not complex expressions. For example, [1,2,3] `zip` [4,5,6] is OK, but not [1,2,3] `zipWith (+)` [4,5,6] Is there any reason other than potential confusion when one of the two backquotes is accidentally omitted? In any case, perhaps some people on this mailing list would appreciate the following implementation of "infix expressions" that Dylan Thurston and I came up with -- as algebraic and perverse as we could manage: infixr 0 -:, :- data Infix f y = f :- y x -:f:- y = x `f` y main = print $ [1,2,3] -: zipWith (+) :- [4,5,6] -- Edit this signature at http://www.digitas.harvard.edu/cgi-bin/ken/sig The trick is that there is no trick.

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Haskell is more known than we might think
by oleg＠pobox.com 29 Jul '02

29 Jul '02

Hello! The other day I received, among other junk mail, coupons for the local 7-eleven store. I subconsciously scanned the envelope, and almost jumped when I read the return address: 7-Eleven, Inc. 2711 North Haskell Avenue Dallas, TX 75204 It seems a rather long Avenue (with at least 27 blocks); presumably it has the Southern part too. Being associated with the most successful worldwide convenience store chain bodes well for the language.

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(no subject)
by Scott J. 28 Jul '02

28 Jul '02

I think I am in the wrong pub. It seems I am alone here. Scott

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Uluslararas� �� FIRSATI..
by �� F�rsat� 28 Jul '02

28 Jul '02

Uluslararası amerikan firması sağlık, kozmetik, gıda ve telekomünikasyon alanında uluslar arası çalışma imkanı tanıyor. Önkoşulsuz, sermayesiz ve risksiz. Dilerseniz ek gelir dilerseniz milyon $ 'lık bir iş; .......ve bağımsız! İlgileniyorsanız. Selim Bengi. Ofis Tel: 0312 232 33 81 pbx. GSM : 0546 265 06 10 : 0542 516 27 65 e-mail: vizyonlife(a)mynet.com

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converting capital letters into small letters
by Karen Y 27 Jul '02

27 Jul '02

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Doubts...
by Pedro L. P. Dias 26 Jul '02

26 Jul '02

Dear Professor: My name is Carlos Alexandre Grimaldi. I'm engineering student at Federal University of Rio de Janeiro, Brazil. I began my studies in Haskell, and I have some doubts which I report here. I'm very gratefully if you could help me. I'm following a book I downloaded from Internet: "A Gentle Introduction to Haskell, Version 98". Following this, I face some problems: - "inc :: Integer -> Integer" don't work - "inc n = n+1" don't work too; - "data Bool = False | True" also...; - "data Color = Red | Green | Blue | Indigo | Violet" also fails. I thought that this commands and definitions must be inside a program, and don't at prompt "prelude>". So, I opened other book, also downloaded from Internet: "The Hugs 98 User Manual", and I tryed: "module Fact where fact :: Integer -> Integer fact n = product [1..n]" thinking that would be created a file "Fact", in which the definitions for "fact" would work. But this also yield an error... So, I ask you: - is necessary the creation of a file where that definitions could work? - is this file a ".hs"? - how can I create a file like this? Which command or editor? - or, if I wrong, why that examples don't work? Thank you very much for your help. Best regards, Carlos A. Grimaldi.

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RE: converting capital letters into small letters
by Garner, Robin 26 Jul '02

26 Jul '02

> 1. How would I convert capital letters into small letters? > > 2. How would I remove vowels from a string? I expect the first problem is actually to convert the upper case letters in a string to lower case, as the single-character version isn't a very interesting problem. A little thought shows that the first problem can be expressed as both a catamorphism or an anamorphism. The anamorphic solution would be [(p,f)] where p as = as == [] and f (a:as) = (makeLowerCase a, bs). The solution to the second problem is clearly a catamorphism, and one solution might be (|[],g|) where g (a:as) = if isVowel a then as else a:as The definitions of 'makeLowerCase' and 'isVowel' are quite simple (assuming English/Ascii, as pointed out in other messages), while finding the prelude functions for the patterns of recursion might take a little more thought. Suitable, possible, as homework questions in an introductory Haskell course ... Robin

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