Re: [Haskell-cafe] Approaches to dependent types (DT)

On Fri, Oct 9, 2009 at 6:11 AM, pat browne wrote: > class Named object name | object -> name where > name :: object -> name > > instance (Eq name, Named object name) => Eq object where > object1 == object2 = (name object1) == (name object2) > This is a type-indexed type. On a modern GHC I would

Re: [Haskell-cafe] Re: Libraries for Commercial Users

On 2009-10-09 20:53 -0600 (Fri), John A. De Goes wrote: > The vast majority of applications being built today are web apps. Right, and the vast majority of these are done in PHP, followed by Ruby and Python. For these languages, the majority of libraries are not native, but C libraries. So this

Re: [Haskell-cafe] Re: Libraries for Commercial Users

On Oct 9, 2009, at 10:07 AM, Duncan Coutts wrote: On Thu, 2009-10-08 at 09:43 -0600, John A. De Goes wrote: Here's a list of libraries that are quite significant to commercial software development in 2009, For the kinds of applications that you would like to build. The vast majority of appli

Re: [Haskell-cafe] HDBC PostgreSQL

No, I was running the following: :module Database.HDBC Database.HDBC.PostgreSQL and the reply was: module `Database.HDBC.PostgreSQL' is not loaded Not sure where to go from here. I'll keep reading. On Fri, Oct 9, 2009 at 4:58 PM, John Goerzen wrote: > Patrick Brannan wrote: >> Prelude> module H

Re: [Haskell-cafe] How do I get this done in constant mem?

On Fri, Oct 9, 2009 at 2:05 PM, wrote: > Hi all, > > I think there is something about my use of the IO monad that bites me, > but I am bored of staring at the code, so here you g.  The code goes > through a list of records and collects the maximum in each record > position. > > > -- test.hs > imp

Re: [Haskell-cafe] Re: Haskell Weekly News

On Fri, Oct 09, 2009 at 05:46:15PM +0900, Benjamin L.Russell wrote: > 2) Instead of posting separately to the Haskell and Haskell-Cafe > mailing lists, it might be better to cross-post, since that way, > readers using newsreaders can have the cross-posted article > automatically marked "read" in th

Re: [Haskell-cafe] CBN, CBV, Lazy in the same final tagless framework

Felipe Lessa wrote: which unfortunately needs {-# LANGUAGE RecursiveDo #-} or some ugliness from mfix But mdo/mfix is awesome! :-( Martijn. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe

Re: [Haskell-cafe] Non-traversable foldables

Ross Paterson wrote: On Fri, Oct 09, 2009 at 04:41:05PM +0200, Martijn van Steenbergen wrote: Can anyone think of datatypes that are Foldable but not Traversable? Set Nice! Thank you all for your answers. Martijn. ___ Haskell-Cafe mailing list Ha

Re: [Haskell-cafe] Different semantics in "identical" do statement?

On Fri, Oct 9, 2009 at 4:25 PM, David Menendez wrote: > On Fri, Oct 9, 2009 at 6:47 PM, staafmeister wrote: >> >> Daniel Peebles wrote: >>> >>> I vaguely remember on IRC someone pointing out that the Parsec monad >>> broke one of the laws. I think return _|_ >> x === _|_ which could be >>> causin

Re: [Haskell-cafe] Different semantics in "identical" do statement?

On Fri, Oct 9, 2009 at 6:47 PM, staafmeister wrote: > > Daniel Peebles wrote: >> >> I vaguely remember on IRC someone pointing out that the Parsec monad >> broke one of the laws. I think return _|_ >> x === _|_ which could be >> causing your problem. I may be wrong though. >> >> > > Confirmed, wor

Re: [Haskell-cafe] What *is* a DSL?

> "Gregg" == Gregg Reynolds writes: Gregg> On Thu, Oct 8, 2009 at 6:08 AM, Colin Paul Adams Gregg> wrote: > > "George" == George Pollard writes: >> George> I'd also like to note that the canonical pronunciation of George> DSL ends in "-izzle". >> >> Whose c

Re: [Haskell-cafe] Different semantics in "identical" do statement?

Daniel Peebles wrote: > > I vaguely remember on IRC someone pointing out that the Parsec monad > broke one of the laws. I think return _|_ >> x === _|_ which could be > causing your problem. I may be wrong though. > > Confirmed, working in the parsec monad Prelude Text.Parsec> runP (do {x <

Re: [Haskell-cafe] What *is* a DSL?

On Thu, Oct 8, 2009 at 6:08 AM, Colin Paul Adams wrote: > > "George" == George Pollard writes: > >George> I'd also like to note that the canonical pronunciation of >George> DSL ends in "-izzle". > > Whose canon? > > Interestingly, I have always assumed the canonical pronunciation of >

Re: [Haskell-cafe] Different semantics in "identical" do statement?

Daniel Peebles wrote: > > I vaguely remember on IRC someone pointing out that the Parsec monad > broke one of the laws. I think return _|_ >> x === _|_ which could be > causing your problem. I may be wrong though. > > This could very well be it. I use lazy eval to construct a function that r

Re: [Haskell-cafe] Different semantics in "identical" do statement?

I vaguely remember on IRC someone pointing out that the Parsec monad broke one of the laws. I think return _|_ >> x === _|_ which could be causing your problem. I may be wrong though. On Fri, Oct 9, 2009 at 5:59 PM, staafmeister wrote: > > > > Ross Mellgren wrote: >> >> In what Monad? >> >> > > P

[Haskell-cafe] Re: Re: What *is* a DSL?

Emil Axelsson wrote: > Ben Franksen skrev: >> minh thu wrote: >>> 2009/10/7 Günther Schmidt : > I've informally argued that a true DSL -- separate from a good API -- > should have semantic characteristics of a language: binding forms, > control structures, abstraction, composition. Some

Re: [Haskell-cafe] Different semantics in "identical" do statement?

Ross Mellgren wrote: > > In what Monad? > > Parsec Monad -- View this message in context: http://www.nabble.com/Different-semantics-in-%22identical%22-do-statement--tp25828319p25828521.html Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com. _

Re: [Haskell-cafe] HDBC PostgreSQL

Patrick Brannan wrote: > Prelude> module HDBC HDBC.PostgreSQL > > Now I would think that the line "Loading package > HDBC-postgresql-2.1.0.0 ... linking ... done." means that the module > is installed correctly, but I still can't execute the :module > statement. > > Does anyone have any ideas abo

Re: [Haskell-cafe] Different semantics in "identical" do statement?

In what Monad? -Ross On Oct 9, 2009, at 5:43 PM, staafmeister wrote: In my program do x <- do blah <- someFunc return blah return $ Constructor x behaves differently from do blah <- someFunc return $ Constructor blah where the dots are identical. I would think that these program

[Haskell-cafe] Different semantics in "identical" do statement?

In my program do x <- do blah <- someFunc return blah return $ Constructor x behaves differently from do blah <- someFunc return $ Constructor blah where the dots are identical. I would think that these programs should behave identically, by the monad laws. The result of my pro

Re: [Haskell-cafe] Setting environment variables on Windows

On Fri, 2009-10-09 at 17:37 +0200, Sönke Hahn wrote: > Hi! > > I need to set an environment variable from Haskell and i would like to do > that > cross-platform. There is System.Posix.Env.setEnv, which does exactly, what i > want on Linux. There is the module System.Environment, which seems to

Re: [Haskell-cafe] Applicative do?

Nicolas Pouillard wrote: Excerpts from Edward Kmett's message of Fri Oct 09 20:04:08 +0200 2009: I have idiom brackets in that toy library already, but the ado syntax is fairly useful if you want to refer to several intermediate results by name. To work with idiom brackets you need to manuall

Re: [Haskell-cafe] Applicative do?

Excerpts from Edward Kmett's message of Fri Oct 09 20:04:08 +0200 2009: > I have idiom brackets in that toy library already, but the ado syntax is > fairly useful if you want to refer to several intermediate results by name. > To work with idiom brackets you need to manually write a big lambda your

Re: [Haskell-cafe] ANN: text 0.5, a major revision of the Unicode text library

oops, for the sake of completeness you also need: textType = mkStringType "Data.Text" - jeremy On Oct 9, 2009, at 10:33 AM, Jeremy Shaw wrote: Sweet! What are the chances of seeing a, instance Data Text, some day? text would be a great type to use with Happstack, because it is far more m

Re: [Haskell-cafe] ANN: text 0.5, a major revision of the Unicode text library

On Fri, Oct 9, 2009 at 1:08 PM, Paulo Tanimoto wrote: > I tried to post a comment to your website, but it may have been lost. > It seems that the description for unlines is picking up a comment that > was meant for lines': > Thanks, yes, Johan sent a patch in to fix that already. Hooray for open

Re: [Haskell-cafe] Happstack + network package issue on the Mac

"Bryan O'Sullivan" writes: > On Fri, Oct 9, 2009 at 7:25 AM, Gregory Collins > wrote: >   > > There's been an open ticket for months; personally I think this is > a job for the C preprocessor, but nobody's written a patch yet. > > Is there an open ticket against the network package? Can

Re: [Haskell-cafe] Happstack + network package issue on the Mac

Bryan O'Sullivan wrote: On Fri, Oct 9, 2009 at 7:25 AM, Gregory Collins > wrote: There's been an open ticket for months; personally I think this is a job for the C preprocessor, but nobody's written a patch yet. Is there an open ticket against the netw

Re: [Haskell-cafe] ANN: text 0.5, a major revision of the Unicode text library

Hi Bryan, On Fri, Oct 9, 2009 at 2:11 AM, Bryan O'Sullivan wrote: > Get it while it's fresh on Hackage, folks! Details of the changes here: > http://bit.ly/1u4UOT > This is superb! I tried to post a comment to your website, but it may have been lost. It seems that the description for unlines is

[Haskell-cafe] How do I get this done in constant mem?

Hi all, I think there is something about my use of the IO monad that bites me, but I am bored of staring at the code, so here you g. The code goes through a list of records and collects the maximum in each record position. -- test.hs import Random import System.Environment (getArgs) import Sy

[Haskell-cafe] Re: Num instances for 2-dimensional types

Joe Fredette wrote: > A ring is an abelian group in addition, with the added operation (*) > being distributive over addition, and 0 annihilating under > multiplication. (*) is also associative. Rings don't necessarily need > _multiplicative_ id, only _additive_ id. Yes, this is how I learned it i

Re: [Haskell-cafe] ANN: text 0.5, a major revision of the Unicode text library

Based on section 5.2 of this paper: http://www.cs.vu.nl/boilerplate/gmap2.pdf I wonder if the Data instance I provided is the best possible option with out modifying SYB. And that the optimal solution would be to extend ConstrRep to support Text as a primitive: data ConstrRep = AlgConstr C

[Haskell-cafe] HDBC PostgreSQL

Hello, I'm getting back into Haskell after an absence of a few years. I'm in the process of trying to connect to postgresql with hdbc-postgresql on a Windows XP box. Seemingly, things installed without a problem, but at the command prompt I get the following: Prelude> :module Database.HDBC Data

Re: [Haskell-cafe] Happstack + network package issue on the Mac

On Fri, Oct 9, 2009 at 7:25 AM, Gregory Collins wrote: > There's been an open ticket for months; personally I think this is a job > for the C preprocessor, but nobody's written a patch yet. Is there an open ticket against the network package? Can someone write a simple standalone repro for me t

Re: [Haskell-cafe] ANN: text 0.5, a major revision of the Unicode text library

On Fri, Oct 9, 2009 at 8:33 AM, Jeremy Shaw wrote: > > What are the chances of seeing a, instance Data Text, some day? I might as well follow up here, since I've sent Jeremy a couple of messages on this subject. I think maybe someone else will have to take a crack at a Data instance for Text,

[Haskell-cafe] Re: ANNOUNCE: htzaar-0.0.1

Tom Hawkins writes: > Sorry, I forgot to add the other modules to the cabal file. Try > htzaar-0.0.2. Thank you, it's working now. jao -- The reasonable man adapts himself to the world; the unreasonable one persists in trying to adapt the world to himself. Therefore all progress depends on th

Re: [Haskell-cafe] CBN, CBV, Lazy in the same final tagless framework

On Fri, Oct 9, 2009 at 1:39 PM, Felipe Lessa wrote: > On Fri, Oct 09, 2009 at 01:27:57PM -0400, David Menendez wrote: >> On Fri, Oct 9, 2009 at 11:12 AM, Felipe Lessa wrote: >> > That's really nice, Oleg, thanks!  I just wanted to comment that >> > I'd prefer to write >> > >> > share :: IO a -> I

Re: [Haskell-cafe] ANN: text 0.5, a major revision of the Unicode text library

On Fri, Oct 9, 2009 at 8:33 AM, Jeremy Shaw wrote: > > What are the chances of seeing a, instance Data Text, some day? text would > be a great type to use with Happstack, because it is far more memory > efficient than String. But it is difficult to do that with out a instance of > Data. Ask, an

Re: [Haskell-cafe] Applicative do?

I have idiom brackets in that toy library already, but the ado syntax is fairly useful if you want to refer to several intermediate results by name. To work with idiom brackets you need to manually write a big lambda yourself and them apply it. If you have a lambda that takes several arguments -- w

Re: [Haskell-cafe] Applicative do?

I'd prefer "idiom brackets" over something do-ish for Applicatives. Conor McBride's SHE already supports them, if you're willing to use a custom preprocessor. On Fri, Oct 9, 2009 at 1:45 PM, Joe Fredette wrote: > The only issue I would have with such a notation is not being able to > visually tel

Re: [Haskell-cafe] Applicative do?

The only issue I would have with such a notation is not being able to visually tell the difference between a monadic function (say, without a explicit type sig, which is how I write parsers), and an applicative one. I'd prefer something like foo = app blah blah If only for some vi

Re: [Haskell-cafe] CBN, CBV, Lazy in the same final tagless framework

On Fri, Oct 09, 2009 at 01:27:57PM -0400, David Menendez wrote: > On Fri, Oct 9, 2009 at 11:12 AM, Felipe Lessa wrote: > > That's really nice, Oleg, thanks!  I just wanted to comment that > > I'd prefer to write > > > > share :: IO a -> IO (IO a) > > share m = mdo r <- newIORef (do x <- m > >    

Re: [Haskell-cafe] Applicative do?

Good trick. I just added 'ado' to my little scheme monad library. ;) -Edward Kmett On Fri, Oct 9, 2009 at 1:06 PM, Philippa Cowderoy wrote: > I do a lot of work with parsers, and want to do more using Applicatives. > That said, I'm finding it a little tedious being forced to use pointless > styl

Re: [Haskell-cafe] Applicative do?

Robert Atkey wrote: On Fri, 2009-10-09 at 18:06 +0100, Philippa Cowderoy wrote: This leads us to the bikeshed topic: what's the concrete syntax? I implemented a simple Camlp4 syntax extension for Ocaml to do this. I chose the syntax: applicatively let x = foo let y = bar

Re: [Haskell-cafe] CBN, CBV, Lazy in the same final tagless framework

On Fri, Oct 9, 2009 at 11:12 AM, Felipe Lessa wrote: > On Thu, Oct 08, 2009 at 12:54:14AM -0700, o...@okmij.org wrote: >> Actually it is possible to implement all three evaluation orders >> within the same final tagless framework, using the same interpretation >> of types and reusing most of the c

Re: [Haskell-cafe] Setting environment variables on Windows

Mmm, that seems like a shortcoming. Well, you could just wrap the C functions yourself, like this (two possibilities, no error checking yet, quick hack): http://hpaste.org/fastcgi/hpaste.fcgi/view?id=10565#a10565 Note that using SetEnvironmentVariable does not seem to be compatible with getEnv, b

Re: [Haskell-cafe] Applicative do?

On Fri, 2009-10-09 at 18:06 +0100, Philippa Cowderoy wrote: > This leads us to the bikeshed topic: what's the concrete syntax? I implemented a simple Camlp4 syntax extension for Ocaml to do this. I chose the syntax: applicatively let x = foo let y = bar in I quite like the word "a

[Haskell-cafe] Applicative do?

I do a lot of work with parsers, and want to do more using Applicatives. That said, I'm finding it a little tedious being forced to use pointless style for a task that's well-suited to having a few names around. The idea of an applicative do notation's been kicked around on #haskell a few times

Re: [Haskell-cafe] Re: Libraries for Commercial Users

On Thu, 2009-10-08 at 09:43 -0600, John A. De Goes wrote: > Here's a list of libraries that are quite significant to commercial > software development in 2009, For the kinds of applications that you would like to build. > but which either do not exist in Haskell, or if they exist, are hard > to

Re: [Haskell-cafe] Re: Haskell Weekly News

Mostly it's been issues with sendmail, I think I have them fixed for this week. (I think...) Thanks for the input! /Joe On Oct 9, 2009, at 4:46 AM, Benjamin L.Russell wrote: Thank you for including my quote (by "dekudekuplex"), and great work so far! Just a couple of minor comments: 1) I

[Haskell-cafe] Setting environment variables on Windows

Hi! I need to set an environment variable from Haskell and i would like to do that cross-platform. There is System.Posix.Env.setEnv, which does exactly, what i want on Linux. There is the module System.Environment, which seems to be cross-platform, but it does not contain functions to manipulat

Re: [Haskell-cafe] ANN: text 0.5, a major revision of the Unicode text library

Sweet! What are the chances of seeing a, instance Data Text, some day? text would be a great type to use with Happstack, because it is far more memory efficient than String. But it is difficult to do that with out a instance of Data. For the time being, I have been hacking it with: insta

Re: [Haskell-cafe] CBN, CBV, Lazy in the same final tagless framework

On Thu, Oct 08, 2009 at 12:54:14AM -0700, o...@okmij.org wrote: > Actually it is possible to implement all three evaluation orders > within the same final tagless framework, using the same interpretation > of types and reusing most of the code save the semantics of lam. That > is where the three or

Re: [Haskell-cafe] Non-traversable foldables

On Fri, Oct 09, 2009 at 04:45:01PM +0200, Henning Thielemann wrote: > Recently I wondered, why Foldable is superclass of Traversable, > since I have examples where 'traverse' makes sense, but 'fold' not. > > http://www.haskell.org/pipermail/libraries/2009-February/011361.html That would be surpri

Re: [Haskell-cafe] Non-traversable foldables

On Fri, Oct 9, 2009 at 10:45 AM, Henning Thielemann < lemm...@henning-thielemann.de> wrote: > > On Fri, 9 Oct 2009, Martijn van Steenbergen wrote: > > Hallo café, >> >> Can anyone think of datatypes that are Foldable but not Traversable? > > Data.Set.Set is a good example. The values contained in

Re: [Haskell-cafe] Non-traversable foldables

On Fri, Oct 09, 2009 at 04:41:05PM +0200, Martijn van Steenbergen wrote: > Can anyone think of datatypes that are Foldable but not Traversable? Set ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-caf

Re: [Haskell-cafe] Non-traversable foldables

On Fri, 9 Oct 2009, Martijn van Steenbergen wrote: Hallo café, Can anyone think of datatypes that are Foldable but not Traversable? If not, what is the purpose of having a separate Foldable class? Recently I wondered, why Foldable is superclass of Traversable, since I have examples where '

[Haskell-cafe] Non-traversable foldables

Hallo café, Can anyone think of datatypes that are Foldable but not Traversable? If not, what is the purpose of having a separate Foldable class? Thanks, Martijn. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/

Re: [Haskell-cafe] Happstack + network package issue on the Mac

Gregory Collins wrote: Sean Leather writes: On Thu, Oct 8, 2009 at 16:35, Gregory Collins wrote: Sean Leather writes: Do you know if it's possible to permanently patch happstack-server? I'm guessing the TH in the patch is used to support multiple versions of the network package. Can w

Re: [Haskell-cafe] Re: ANNOUNCE: htzaar-0.0.1

On Fri, Oct 9, 2009 at 2:24 PM, Jose A. Ortega Ruiz wrote: > > Hi, > > When i try to cabal install htzaar i get the following error: > > src/Main.hs:11:7: >    Could not find module `Play': >      Use -v to see a list of the files searched for. > cabal: Error: some packages failed to install: > ht

Re: [Haskell-cafe] Happstack + network package issue on the Mac

Sean Leather writes: > On Thu, Oct 8, 2009 at 16:35, Gregory Collins wrote: > > Sean Leather writes: > > > We have run into an issue that it seems other people have already > > found but has apparently not been resolved, yet. It manifests as with > > the error "HTTP request f

Re: [Haskell-cafe] Re: ANNOUNCE: htzaar-0.0.1

В сообщении от 09 октября 2009 16:24:49 Jose A. Ortega Ruiz написал: > Hi, > > When i try to cabal install htzaar i get the following error: > > src/Main.hs:11:7: > Could not find module `Play': > Use -v to see a list of the files searched for. > cabal: Error: some packages failed to in

Re: [Haskell-cafe] Can HXT and Parsec 3 be used in the same library?

On Sun, 2009-10-04 at 10:32 -0700, John Millikin wrote: > I'm writing a library that needs to parse both plain text (with Parsec) > and XML (with HXT). HXT's .cabal file specifies that it only works with > parsec (>= 2.1 && < 3), but it still builds when I depend on parsec >= > 3. It's only during

[Haskell-cafe] Approaches to dependent types (DT)

Hi, I am trying to understand the concept of dependent types as described in Haskell literature (Hallgren 2001),(Hinze,Jeuring et al. 2006). I am particularly interested in understanding two flavours of dependency mentioned by Hinze et al: 1) Types depending on values called dependent types 2) Type

[Haskell-cafe] Re: ANNOUNCE: htzaar-0.0.1

Hi, When i try to cabal install htzaar i get the following error: src/Main.hs:11:7: Could not find module `Play': Use -v to see a list of the files searched for. cabal: Error: some packages failed to install: htzaar-0.0.1 failed during the building phase. The exception was: exit: ExitF

Re: [Haskell-cafe] type inference question

2009/10/9 wren ng thornton : > Cristiano Paris wrote: >> >> On Thu, Oct 8, 2009 at 12:48 PM, Lennart Augustsson wrote: >>> >>> The reason a gets a single type is the monomorphism restriction (read >>> the report). >>> Using NoMonomorphismRestriction your example with a works fine. >> >> Could you e

Re: [Haskell-cafe] Happstack + network package issue on the Mac

On Thu, Oct 8, 2009 at 16:35, Gregory Collins wrote: > Sean Leather writes: > > > We have run into an issue that it seems other people have already > > found but has apparently not been resolved, yet. It manifests as with > > the error "HTTP request failed with: Unsupported socket". The problem >

Re: [Haskell-cafe] ANNOUNCE: htzaar-0.0.1

On Thu, Oct 8, 2009 at 12:56 AM, Tom Hawkins wrote: > Known bugs: Occasionally HTZAAR throws a Prelude.head: empty list. > I'm still trying to track this down. I used the following function to track down a similar problem: myhead :: String -> [a] -> a myhead msg [] = error msg myhead _ (x:_) = x

Re: [Haskell-cafe] type inference question

Cristiano Paris wrote: On Thu, Oct 8, 2009 at 12:48 PM, Lennart Augustsson wrote: The reason a gets a single type is the monomorphism restriction (read the report). Using NoMonomorphismRestriction your example with a works fine. Could you explain why, under NoMonomorphismRestriction, this type

[Haskell-cafe] Re: Any example of concurrent haskell application?

Daryoush Mehrtash wrote: > I am trying to learn more about concurrent applications in Haskell by > studying an existing a real application source code. I would very much > appreciate if you can recommend an application that you feel has done a good > job in implementing a real time application in

[Haskell-cafe] Re: Haskell Weekly News

Thank you for including my quote (by "dekudekuplex"), and great work so far! Just a couple of minor comments: 1) It might be useful for referencing by subject if you could include the issue number and date in the subject line (e.g., " Haskell Weekly News: Issue 131 - September 25, 2009") instead

Re: [Haskell-cafe] Any example of concurrent haskell application?

Daryoush Mehrtash wrote: I am trying to learn more about concurrent applications in Haskell by studying an existing a real application source code. I would very much appreciate if you can recommend an application that you feel has done a good job in implementing a real time application in Has

[Haskell-cafe] ANN: text 0.5, a major revision of the Unicode text library

Get it while it's fresh on Hackage, folks! Details of the changes here: http://bit.ly/1u4UOT ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe