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The Haskell Cafe
August 2007 - page 1
Ryan Ingram — 118598184201 Aug 2007
Background: I participated in this year's ICFP programming contest<http://www.icfpcontest.org>and our team did quite well, coming in 37th. O...
Backpatching (6 Replies)
Thomas Conway — 118599436401 Aug 2007*
Hi All, One of the things I've been working on lately is some ASN.1 stuff.One of the first things I wrote in Haskell was an ASN.1 parser. It only ...
oleg — 118600815401 Aug 2007
Dan Doel wrote about `inverting' a parser -- first, a pure parser consuming a string and later a parser written in a monadic style and consuming a...
Greg Meredith — 118602009002 Aug 2007
Arie, Thanks for your thoughtful reply. Comments in-lined. Best wishes, --greg Date: Thu, 2 Aug 2007 03:06:51 +0200 (CEST)Sorry, i was being as fast a...
monads and groups -- instead of loops (7 Replies)
Greg Meredith — 118603082402 Aug 2007*
Haskellians, Though the actual metaphor in the monads-via-loops doesn't seem to fly with this audience, i like the spirit of the communication and...
Cartesian product of a Set (7 Replies)
Andy Gimblett — 118603118602 Aug 2007*
Hi all, Is this a reasonable way to compute the cartesian product of a Set?It's a fairly "obvious" way to do it, but I wondered if there...
Some Haskell platformish questions (12 Replies)
David Pollak — 118605057202 Aug 2007*
Howdy, I'm considering building a desktop app using Haskell. The primary target for the app is Windows, but if it runs on Linux and Mac (Intel and...
Installing FreeGLUT (1 Reply)
Ronald Guida — 118605095002 Aug 2007*
Hi, I am trying to use freeglut with GHCi 6.6.1, and I'm stuck. I downloaded freeglut 2.4.0 and compiled it. I am on a Windows XP machine, and I f...
Primitive Recursive Algebraic Types (2 Replies)
Alexteslin — 118607452502 Aug 2007*
Hi, I am doing some simple exercises about recursive algebraic types and this particular exercise asks to define a function which counts the number of...
Björn Buckwalter — 118607622002 Aug 2007*
Dear all, I am pleased to announce version 0.6 of the Dimensional library. Dimensional is a library providing data types for performing arithmetic wit...
Björn Buckwalter — 118608290302 Aug 2007
Which implies that CGS is applicable to temperatures... what is the (conventional) dimension of temperature in CGS? Is it the same as for Energy (L^2 ...
positive Int (9 Replies)
brad clawsie — 118608788002 Aug 2007*
as far as i know, the haskell standard does not define a basic Int type that is limited to positive numbers. would a type of this kind not potentially...
Greg Meredith — 118609487202 Aug 2007*
Ok,This is more than a little revisionist. Monads have been the subject of mathematical study before people had an inkling that they might apply to pr...
GHC, GLUT and OS X (5 Replies)
Paul L — 118609756402 Aug 2007*
I'm trying to get cross platform GLUT/OpenGL program to run, but even the simplest code hang on OS X with GHC 6.6 or GHC 6.6.1 import Graphics.UI....
Greg Meredith — 118614985603 Aug 2007
Haskellians, i am delighted to see vigorous exchange that actually resulted in change of positions. i confess i was going to give up, but glad others ...
When is waitForProcess not necessary? (8 Replies)
Dave Bayer — 118616386803 Aug 2007*
If one is calling runInteractiveCommand for a "sure-thing" returning a small amount of output (say, "ls" for a modest directory...
Question about arrows (2 Replies)
Lewis-Sandy, Darrell — 118619244804 Aug 2007*
Is there a class property of the Control.Arrow class that represents the evaluatation of an arrow: eval :: (Arrow a)=>a b c->b->c I am writin...
Shin-Cheng Mu — 118624630104 Aug 2007*
I am curious about the possibility of developing Haskell programs spontaneously with proofs about their properties and have the type checker verify th...
Tim Newsham — 118624912804 Aug 2007
I noticed that there is no official FreeBSD/amd64 port yet, although there's a binary with a working "ghc" but non-working "ghci....
Haskell FCGI server. (1 Reply)
George Moschovitis — 118627035104 Aug 2007*
Dear devs, is it possible to create a FCGI server that listens to a specific port using the Haskell FCGI library? The front end web server would then ...
Brian Hulley — 118635450105 Aug 2007
I suggest the execution of (a) should be done immediately before the action obtained by applying the monadic function whose argument it is part of: do...
Perfect example (6 Replies)
Jon Harrop — 118637751806 Aug 2007*
Any suggestions for a perfect example that uniquely demonstrates the benefits of the Haskell language compared to other languages?...
c2hs and structs? (1 Reply)
Magnus Therning — 118637792106 Aug 2007*
I can't seem to find any information on how to deal with C functions that return a (pointer to a) struct. C2hs tells me there's no automatic s...
Navigating Haddock (3 Replies)
David Pollak — 118637961106 Aug 2007*
Howdy, As I'm starting to learn the Haskell libraries, I'm having a less than fun time trying to figure out what functions operate on what typ...
Alex Jacobson — 118638498406 Aug 2007*
This implementation of calculating 10000 primes (compiled with GHC -O2) is 25% slower than the naive python implementation. Shouldn't it be faster...
Matthew Fluet (ICFP Publicity Chair — 118640078806 Aug 2007
== Call for Participation The 12th ACM SIGPLAN International Conference on Functional Programming (ICFP 2007) http://www.informatik.uni-bonn.de/~ralf/...
Paul Hudak — 118640504006 Aug 2007
Original Message Subject: PADL 2008: Call for Papers Date: Sat, 4 Aug 2007 19:25:58 -0500 (CDT) From: Paul Hudak [ Colleagues, note that this will be ...
Type without a data constructor? (5 Replies)
Rahul Kapoor — 118642997206 Aug 2007*
Most examples for defining algebraic types include data constructors like so: data Tree a = Tip | Node a (Tree a) (Tree a) I by mistake defined a...
Java 1.5 parser in Haskell (1 Reply)
tim.b — 118643621706 Aug 2007*
Does anyone know of a fairly complete Java 1.5 parser and abstract syntax in Haskell? I've looked around quite a bit to no avail. Thanks, - Tim...
combinators for a simple grammar (2 Replies)
Rahul Kapoor — 118644014306 Aug 2007*
I am having problems coming up with nice combinators for a simple DSEL. The abstract syntax is simply given by the types: data SearchCondition = Searc...
Newbie question: "multi-methods" in Haskell (7 Replies)
peterv — 118644731207 Aug 2007*
In de book Modern C++ design, Andrei Alexandrescu writes that Haskell supports multi-methods http://books.google.com/books?id=aJ1av7UFBPwC... n+C%2B%2...
Hugh Perkins — 118645327507 Aug 2007
Hi, Really interested in doing a phd on threading. Any ideas how I'd go about doing/applying for that? Basically, threading seems to be the cuttin...
Monad for Set? (2 Replies)
Ronald Guida — 118645760907 Aug 2007*
Hi, I'm pondering, is it possible to define a Set monad analogous to the List monad? My thinking is as follows: * "fmap f x" would apply...
Donald Bruce Stewart — 118646607607 Aug 2007
...
Type classes: Missing language feature? (3 Replies)
DavidA — 118648410007 Aug 2007*
Hi, there's something I'm trying to do with type classes that seems to fit very naturally with my mental model of type classes, but doesn...
creating graphics the functional way (13 Replies)
Frank Buss — 118653239508 Aug 2007*
I've created a small program to compose images with combinators: http://www.frank-buss.de/haskell/OlympicRings... It produces TGA output, but I...
OS swapping and haskell data structures (7 Replies)
Alex Jacobson — 118654353808 Aug 2007*
If you create a Data.Map or Data.Set larger than fits in physical memory, will OS level swapping enable your app to behave reasonably or will things j...
Dusan Kolar — 118654535708 Aug 2007
Hello all, Maybe this is a wrong place to report, but I have repeatedly performed "funny" calculation in GHCi with strange time report. The ...
peterv — 118656509508 Aug 2007*
Kaveh> "A monad is like a loop that can run a new function against its variable in each iteration." I?m an imperative programmer learning...
mutually recursive types (3 Replies)
rodrigo.bonifacio — 118657213808 Aug 2007*
Hi, I am learning the haskell programming language and had tried to define the following types: type Scenario = (String, String, [Step]) type Step = (...
Newbie question (again!) about phantom types (4 Replies)
peterv — 118658207908 Aug 2007*
Im having difficulty to understand what phantom types are good for. Is this just for improving runtime performance? I read the wiki, and it says ...
Defining new operators (2 Replies)
rodrigo.bonifacio — 118658238508 Aug 2007*
Hello, I have created the following function: dist :: String -> [[String]] -> [[String]] dist x y = [ x:e | e<-y ] eg.: dist "1M...
Using HList Records (1 Reply)
Rahul Kapoor — 118661241108 Aug 2007*
Using The Darcs version of HList (http://darcs.haskell.org/HList/), I can do simple things with (H)lists just fine, so --angus = Key 42 -- .*. Name ...
Using haskell with emacs (10 Replies)
Paulo J. Matos — 118662621609 Aug 2007*
Hi all, I'm starting to learn haskell by my own, being currently mostly a Common Lisp, Scheme, C++ programmer... I've got the haskell emacs mo...
(no subject) (1 Reply)
Thomas Hartman — 118666879309 Aug 2007*
In the following code which uses template haskell, how can I get back the macro-expanded code generated from $(inferStartState ''MyState) I *c...
Operator overloading (1 Reply)
rodrigo.bonifacio — 118666948909 Aug 2007*
Hi all. I want to overload the operator "^" for working instead of the following "+++" operator: (+++) :: String -> [[String]] ...
Slow IO or bad code? (10 Replies)
Vimal — 118667192309 Aug 2007*
Hi I am practicing writing code in haskell, by solving problems at this site. http://spoj.pl. The problem http://spoj.pl/problems/FASHION , is pretty ...
New Eq instance (3 Replies)
rodrigo.bonifacio — 118667218209 Aug 2007*
Hello, I had defined the follwing data type: data Step = Step Id Scenario Action State Response How can I define Step as an "Eq Instance", i...
how can I get template haskell macro-expanded code from inferStartState? (repeated post, now with subject) (2 Replies)
Thomas Hartman — 118667282209 Aug 2007*
(sorry, forgot the subject on my first post) In the following code which uses template haskell, how can I get back the macro-expanded code generated f...
Peter Verswyvelen — 118668041409 Aug 2007*
I was writing some haskell code for fun to solve some "knights and knaves" problems, and I have troubles with http://en.wikipedia.org/wiki/K...