July 2010 - Haskell-Cafe

List manager and duplicate copies of messsages
by José Romildo Malaquias 21 Jul '10

21 Jul '10

Hello. I have noticed that I do not receive duplicate copies of messages from haskell-cafe, although "Avoid duplicate copies of messages?" is set to "No" in the mailing list membership configuration. I want the copies because I archive all the mailing list messages with procmail based on the "X-BeenThere" header line. Has anybody else seen this behaviour, or am I missing anything? Is there any problems with the mailing list manager? Regards, Romildo -- Computer Science Department Universidade Federal de Ouro Preto, Brasil

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Re: [Haskell-cafe] Test. Ignore.
by "José Romildo Malaquias" 21 Jul '10

21 Jul '10

> ----- Original Message ----- > From: José Romildo Malaquias <j.romildo(a)gmail.com> > To: José Romildo Malaquias <romildo(a)operamail.com> > Cc: haskell-cafe(a)haskell.org > Subject: Re: [Haskell-cafe] Test. Ignore. > Date: Wed, 21 Jul 2010 13:33:34 -0300 > > > On Wed, Jul 21, 2010 at 01:25:19PM -0300, "José Romildo Malaquias" wrote: > > > ----- Original Message ----- > > > From: "José Romildo Malaquias" <romildo(a)operamail.com> > > > To: "José Romildo Malaquias" <j.romildo(a)gmail.com> > > > Cc: haskell-cafe(a)haskell.org > > > Subject: Re: [Haskell-cafe] Test. Ignore. > > > Date: Wed, 21 Jul 2010 13:09:16 -0300 > > > > > > ----- Original Message ----- > > > > From: José Romildo Malaquias <j.romildo(a)gmail.com> > > > > To: José Romildo Malaquias <romildo(a)operamail.com> > > > > Cc: haskell-cafe(a)haskell.org > > > > Subject: Re: [Haskell-cafe] Test. Ignore. > > > > Date: Wed, 21 Jul 2010 13:01:03 -0300 > > > > > > > > > > > > On Wed, Jul 21, 2010 at 12:53:53PM -0300, "José Romildo Malaquias" wrote: > > > > > Please, ignore this message. > > > > > > > > Replying to the list and to the sender, to see if he gets both messages > > > > using a non gmail account. > > > > I confirm that I received only one copy of the above message, > > that > was sent directly to my email address at operamail.com. I > > did not > receive any copy from the mailing list manager. > > > > Romildo (at opera.com) > > > > That was expected, as by default the "Avoid duplicate copies of > > messages?" option is set to "Yes" in the mailing list membership > > configuration. Now I have just set it to "No", and I expect to receive > > both copies next time someone from the mailing list "replies to all" > > to one of my messages. > > > > Romildo at operamail.com > > Replying to all. > > Romildo at gmail.com Well, romildo at operamail.com received both copies of the message. So the list manager worked as expected. Romildo at operamail.com -- _______________________________________________ Surf the Web in a faster, safer and easier way: Download Opera 9 at http://www.opera.com

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Re: [Haskell-cafe] Test. Ignore.
by "José Romildo Malaquias" 21 Jul '10

21 Jul '10

> ----- Original Message ----- > From: "José Romildo Malaquias" <romildo(a)operamail.com> > To: "José Romildo Malaquias" <j.romildo(a)gmail.com> > Cc: haskell-cafe(a)haskell.org > Subject: Re: [Haskell-cafe] Test. Ignore. > Date: Wed, 21 Jul 2010 13:09:16 -0300 > > > > ----- Original Message ----- > > From: José Romildo Malaquias <j.romildo(a)gmail.com> > > To: José Romildo Malaquias <romildo(a)operamail.com> > > Cc: haskell-cafe(a)haskell.org > > Subject: Re: [Haskell-cafe] Test. Ignore. > > Date: Wed, 21 Jul 2010 13:01:03 -0300 > > > > > > On Wed, Jul 21, 2010 at 12:53:53PM -0300, "José Romildo Malaquias" wrote: > > > Please, ignore this message. > > > > Replying to the list and to the sender, to see if he gets both messages > > using a non gmail account. > > I confirm that I received only one copy of the above message, that > was sent directly to my email address at operamail.com. I did not > receive any copy from the mailing list manager. > > Romildo (at opera.com) That was expected, as by default the "Avoid duplicate copies of messages?" option is set to "Yes" in the mailing list membership configuration. Now I have just set it to "No", and I expect to receive both copies next time someone from the mailing list "replies to all" to one of my messages. Romildo at operamail.com -- _______________________________________________ Surf the Web in a faster, safer and easier way: Download Opera 9 at http://www.opera.com

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Re: [Haskell-cafe] Test. Ignore.
by "José Romildo Malaquias" 21 Jul '10

21 Jul '10

> ----- Original Message ----- > From: José Romildo Malaquias <j.romildo(a)gmail.com> > To: José Romildo Malaquias <romildo(a)operamail.com> > Cc: haskell-cafe(a)haskell.org > Subject: Re: [Haskell-cafe] Test. Ignore. > Date: Wed, 21 Jul 2010 13:01:03 -0300 > > > On Wed, Jul 21, 2010 at 12:53:53PM -0300, "José Romildo Malaquias" wrote: > > Please, ignore this message. > > Replying to the list and to the sender, to see if he gets both messages > using a non gmail account. I confirm that I received only one copy of the above message, that was sent directly to my email address at operamail.com. I did not receive any copy from the mailing list manager. Romildo (at opera.com) -- _______________________________________________ Surf the Web in a faster, safer and easier way: Download Opera 9 at http://www.opera.com

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Test. Ignore.
by "José Romildo Malaquias" 21 Jul '10

21 Jul '10

Please, ignore this message. Romildo -- _______________________________________________ Surf the Web in a faster, safer and easier way: Download Opera 9 at http://www.opera.com

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Finding zipper for custom tree
by Sergey Mironov 21 Jul '10

21 Jul '10

Hello list! I am trying to understand zipper concept using papers like [1] and [2]. Though main idea looks clear, I still have a problem in applying it for custom data types. Please help me with deriving Zipper-type from > data DTree a = P | D [(a, DTree)] Looking in [1] ('Zippers via Differentiation' chapter) I tried to do the following: 1. Find a DTreeF type which is a pattern functor ([2], chapter 2.1) of my DTree 2. Write DTreeF in 'algebraic' form (using '+' and '*') 3. Find DTreeF' - "derivative" of DTreeF 4. Define my zipper type using list of DTreeF' Step 1 likely ends with > data DTreeF a x = P | D [(a,x)] [2] says that using this pattern functor one could build a fixed-point version of DTree: > data Fix f = In {out :: (f (Fix f))} > data DTreeFP = Fix DTreeF but seems that I have nothing to do with it right now. Step 2 is my main question: In [1] authors did it for binary tree: data Tree a = Leaf a | Bin (Tree a) (Tree a) data TreeF a x = Leaf a | Bin x x and thus TreeF = a + x * x TreeF' = x + x My DTree has inner list of tuples. How should I rewrite it in terms of '+' and '*' ? Any comments are welcome! [1] - http://en.wikibooks.org/wiki/Haskell/Zippers [2] - http://people.cs.uu.nl/andres/Rec/MutualRec.pdf -- Thanks, Sergey

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Merge hsql and HDBC -- there can only be one!
by Christopher Done 21 Jul '10

21 Jul '10

One thing that would be nice is a unification of the general database libraries hsql and HDBC. What is the difference between them? Why are there two, and why are there sets of drivers for both (duplication of effort?)? I've used both in the past but I can't discern a real big difference (I used the hsql-sqlite library and the HDBC-postgresql library, whichever worked...). It seems the best thing to do is either actively merge them together and encourage the community to move from one to the other -- judging from what I've read HDBC is more up to date and newer than hsql -- or have some documentation with damn good reasons to choose one or the other, because currently this is a needless source of confusion and possible duplication of effort for Haskell's database libraries. I wasn't going to post until I'd actually researched the difference myself properly but I didn't get chance to have a look over the weekend, but I thought I'd pose the question. Do people actually care about this?

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Re: Tiger compiler in Haskell: annotating abstract syntax tree
by oleg＠okmij.org 21 Jul '10

21 Jul '10

Jose' Romildo Malaquias wrote: > I am writing here to ask suggestions on how to annotate an ast with > types (or any other information that would be relevant in a compiler > phase) in Haskell. There is also a general way of annotating AST post factum, described in http://okmij.org/ftp/Algorithms.html#tree-annot The method lets one attach arbitrarily many annotations to an already built AST, *without* the need to change the definition of the datatype. One does not even have to anticipate annotations! The method would work with your AST > data Exp > = IntExp Integer > | VarExp Symbol > | AssignExp Symbol Exp as _it is_, without any modifications -- neither to the data type definition, nor to the tree. The method was demonstrated when writing a compiler of sorts: annotating an AST with an inferred type for each node. If the type inference fails, we can still print out the inferred types for the good subexpressions.

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lambda terms in which the variables are positions in lambda terms
by Greg Meredith 21 Jul '10

21 Jul '10

Dear Haskellians, The following code may provide some amusement. i offer a free copy of Barwise's Vicious Circles to the first person to derive deBruijn indices from this presentation. Best wishes, --greg -- -*- mode: Haskell;-*- -- Filename: Term.hs -- Authors: lgm -- Creation: Tue Jul 20 16:37:37 2010 -- Copyright: Not supplied -- Description: -- ------------------------------------------------------------------------ module Generators( Term , MuTerm , DoTerm , ReflectiveTerm , TermLocation , ClosedTermLocation , ClosedReflectiveTerm , unfoldLocation , unfoldTerm , makeMention , makeAbstraction , makeApplication , generateTerms ) where -- M[V,A] = 1 + V + VxA + AxA data Term v a = Divergence | Mention v | Abstraction v a | Application a a deriving (Eq, Show) -- \mu M data MuTerm v = MuTerm (Term v (MuTerm v)) deriving (Eq, Show) -- \partial \mu M data DoTerm v = Hole | DoAbstraction v (DoTerm v) | DoLeftApplication (DoTerm v) (MuTerm v) | DoRightApplication (MuTerm v) (DoTerm v) deriving (Eq, Show) -- first trampoline data ReflectiveTerm v = ReflectiveTerm (MuTerm (DoTerm v, ReflectiveTerm v)) deriving (Eq, Show) -- second trampoline data TermLocation v = TermLocation ((DoTerm v), (ReflectiveTerm v)) deriving (Eq, Show) -- first bounce data ClosedTermLocation = ClosedTermLocation (TermLocation ClosedTermLocation) deriving (Eq, Show) -- second bounce data ClosedReflectiveTerm = ClosedReflectiveTerm (ReflectiveTerm ClosedTermLocation) deriving (Eq, Show) -- the isomorphisms implied by the trampolines unfoldLocation :: ClosedTermLocation -> ((DoTerm ClosedTermLocation), (ReflectiveTerm ClosedTermLocation)) unfoldLocation (ClosedTermLocation (TermLocation (k, t))) = (k, t) unfoldTerm :: ClosedReflectiveTerm -> (MuTerm ((DoTerm ClosedTermLocation), (ReflectiveTerm ClosedTermLocation))) unfoldTerm (ClosedReflectiveTerm (ReflectiveTerm muT)) = muT -- variable mention ctor makeMention :: ClosedTermLocation -> ClosedReflectiveTerm makeMention ctl = (ClosedReflectiveTerm (ReflectiveTerm (MuTerm (Mention (unfoldLocation ctl))))) -- abstraction ctor makeAbstraction :: ClosedTermLocation -> ClosedReflectiveTerm -> ClosedReflectiveTerm makeAbstraction ctl crt = (ClosedReflectiveTerm (ReflectiveTerm (MuTerm (Abstraction (unfoldLocation ctl) (unfoldTerm crt))))) -- application ctor makeApplication :: ClosedReflectiveTerm -> ClosedReflectiveTerm -> ClosedReflectiveTerm makeApplication crtApplicad crtApplicand = (ClosedReflectiveTerm (ReflectiveTerm (MuTerm (Application (unfoldTerm crtApplicad) (unfoldTerm crtApplicand))))) -- a simple test generateTerms :: () -> [ClosedReflectiveTerm] generateTerms () = -- x [(makeMention (ClosedTermLocation (TermLocation (Hole, ReflectiveTerm (MuTerm Divergence))))), -- \x -> x (makeAbstraction (ClosedTermLocation (TermLocation (Hole, ReflectiveTerm (MuTerm Divergence)))) (makeMention (ClosedTermLocation (TermLocation (Hole, ReflectiveTerm (MuTerm Divergence)))))), -- ((\x -> x)(\x -> x)) (makeApplication (makeAbstraction (ClosedTermLocation (TermLocation (Hole, ReflectiveTerm (MuTerm Divergence)))) (makeMention (ClosedTermLocation (TermLocation (Hole, ReflectiveTerm (MuTerm Divergence)))))) (makeAbstraction (ClosedTermLocation (TermLocation (Hole, ReflectiveTerm (MuTerm Divergence)))) (makeMention (ClosedTermLocation (TermLocation (Hole, ReflectiveTerm (MuTerm Divergence)))))))] -- L.G. Meredith Managing Partner Biosimilarity LLC 1219 NW 83rd St Seattle, WA 98117 +1 206.650.3740 http://biosimilarity.blogspot.com

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[SOLVED] Default Curl call fails with CurlSSLConnectError
by aditya siram 20 Jul '10

20 Jul '10

Hi all, Just wanted to document this in case others stumble across it. On Ubuntu Lucid "curlGetString "https://<some url>" []" can sometimes fail with (CurlSSLConnectError,""). Setting SSL to version 3 manually fixes the problem: "curlGetString "https://<some-url>" [CurlSSLVersion 3]". This might also be of interest to the library maintainer, and Don Stewart whose download-curl package, because it is a wrapper around the curl package, exhibits the same behavior. thanks ... -deech

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