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Problem with Haddock
by Daniel Fischer 08 Mar '05

08 Mar '05

Hi, I have the problem that I can't haddock literate modules (latex-style), > haddock -h -o docs Test.lhs Test.lhs:1:1: Parse error the file begins with "\begin{code}". Does anybody know what's up and what to do about it? Furthermore, in the documentation of ghc-6.4.2005..., only four modules from base/GHC are included, in the documentation for ghc-6.2.2 there were 29. In particular, the absence of GHC.List, GHC.Show and GHC.Read is extremely annoying. Any suggestions how to remedy this? Thanks in advance, Daniel

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RE: [Haskell-cafe] Problem with Haddock
by Simon Marlow 08 Mar '05

08 Mar '05

On 08 March 2005 15:26, Daniel Fischer wrote: > I have the problem that I can't haddock literate modules > (latex-style), >> haddock -h -o docs Test.lhs > Test.lhs:1:1: Parse error > > the file begins with "\begin{code}". > > Does anybody know what's up and what to do about it? Haddock doesn't understand literate files on its own. The documentation describes how to get around this... er, well the documentation in CVS describes how to get around this, but the 0.6 docs on the web don't. Here's the relevant text: <section id="cpp"> <title>Using literate or pre-processed source</title> <para>Haddock only accepts plain, non-literate, Haskell source. This means that if you program in Literate Haskell, or you need to use the C pre-processor in your Haskell source, then you need to pre-process the files before feeding them to Haddock. This is easily accomplished using GHC; for example, suppose we have a Literate Haskell source file <filename>Foo.lhs</filename>, on which we also need to run the C pre-processor:</para> <screen> $ ghc -cpp -E -optP-P -D__HADDOCK__ Foo.lhs -o Foo.hs $ haddock -h Foo.hs ... </screen> <para>The <option>-E</option> option to GHC says "stop after pre-processing", the <option>-cpp</option> option turns on the C pre-processor, the <option>-optP-P</option> option tells the C pre-processor not to leave any extra dropping behind (see the description of the <option>-P</option> option in the gcc manual for details), and the <option>-D__HADDOCK__</option> option defines the symbol <literal>__HADDOCK__</literal> when pre-processing (this is sometimes handy if you need to any pre-processing conditionals in your source which depend on whether the source is going to be fed to Haddock).</para> </section> Cheers, Simon

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tuples and Show in GHC
by Stijn De Saeger 07 Mar '05

07 Mar '05

hi all, Is there a principled reason why in GHC tuples with up to five elements automatically derive from the Show class but from six elements and up they don't anymore? If this is not a bug I would be very curious to hear what the reasoning behind this is.... below is an example of said behaviour : > type MyInt1 = (Int,Int,Int,Int,Int) > myInt1 :: MyInt1 > myInt1 = (1,2,3,4,5) > type MyInt2 = (Int,Int,Int,Int,Int,Int) > myInt2 :: MyInt2 > myInt2 = (1,2,3,4,5,6) .... *HS> myInt1 Loading package haskell98 ... linking ... done. (1,2,3,4,5) *HS> myInt2 <interactive>:1: No instance for (Show MyInt2) arising from use of `print' at <interactive>:1 In a 'do' expression: print it *HS> stijn.

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RE: [Haskell-cafe] tuples and Show in GHC
by Simon Peyton-Jones 07 Mar '05

07 Mar '05

No principled reason. I wish there was no limit, which would involve generating code on the fly for instances that weren't pre-generated, but I never got around to implementing that. So you have to stop somewhere. Actually the Report says it should have Show instances up to 15 at least, but GHC doesn't. That isn't deliberate, and I guess we should fix it. Simon | -----Original Message----- | From: haskell-cafe-bounces(a)haskell.org [mailto:haskell-cafe-bounces@haskell.org] On Behalf Of Stijn | De Saeger | Sent: 06 March 2005 09:40 | To: haskell-cafe(a)haskell.org | Subject: [Haskell-cafe] tuples and Show in GHC | | hi all, | | Is there a principled reason why in GHC tuples with up to five | elements automatically derive from the Show class but from six | elements and up they don't anymore? If this is not a bug I would be | very curious to hear what the reasoning behind this is.... | below is an example of said behaviour : | | > type MyInt1 = (Int,Int,Int,Int,Int) | > myInt1 :: MyInt1 | > myInt1 = (1,2,3,4,5) | > type MyInt2 = (Int,Int,Int,Int,Int,Int) | > myInt2 :: MyInt2 | > myInt2 = (1,2,3,4,5,6) | | .... | | *HS> myInt1 | Loading package haskell98 ... linking ... done. | (1,2,3,4,5) | *HS> myInt2 | | <interactive>:1: | No instance for (Show MyInt2) | arising from use of `print' at <interactive>:1 | In a 'do' expression: print it | *HS> | | stijn. | _______________________________________________ | Haskell-Cafe mailing list | Haskell-Cafe(a)haskell.org | http://www.haskell.org/mailman/listinfo/haskell-cafe

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ANN: HAppS -- Haskell Application Server v 0.3
by S. Alexander Jacobson 04 Mar '05

04 Mar '05

HAppS is a Haskell library for building Internet applications, featuring: * HAppS.ACID: Guarantee application integrity in the face of unplanned outages using this module's integrated write-ahead logging and checkpointing framework. * HAppS.DBMS: Do relational operations in Haskell (rather than SQL) on Haskell sets (outside the IO Monad). Define custom indices for your Haskell datatypes (e.g. geographic/geometric types). Use in combination with ACID for a robust relational DBMS customized for your application. * HAppS.Protocols: Expose your application using as an HTTP server and/or by recieving and sending SMTP. Changes since 0.2: HAppS Changes * Much cleaner interface for ACID transaction handlers * DBMS operators that look more like HaskellDB operators * SMTP send errors are exposed for use in future reliable deliver implementation * ACID callbacks disabled. Framework in place for total order on callbacks. * SideEffect queues are now algrebraic types rather than strings. * Parametrized HTTP using XML ToElement and HTTP ToMessage FromMessage and ToURI classes (you write transaction handlers in terms of Haskell types and the system takes care of exposing them for HTTP) * Parametrized HTTP response now has type (ToURL url,ToMessage msg)=>Response url message Framework takes care of automatically translating relative URLs to absolute URLs. Answers to questions a few people have asked: * Compare HAppS.DBMS with HaskellDB HaskellDB is really optimal if you want to talk to external databases. HAppS.DBMS is really good if you want to do relational operations on Haskell Sets without going to the IO monad. * Compare HAppS.ACID to STM Use STM if all your IO operations have a two-phase-commit interface. Use HAppS.ACID if your IO interfaces are not transactional. Instead HAppS.ACID gives you multi-queue, at-least-once execution of side-effects, and a total order on their callbacks. There is no rollback semantic because you can't unsend email. * Compare HAppS.Protocols.SMTP to Peter Simon's Postmaster Postmaster is trying to be a full fledged MTA. SMTP is trying simply to give you SMTP receive/send functionality in your applications. Neither yet has a queuehandler. We both hope to merge lessons learned soon. * Compare HAppS.Protocols.HTTP to Warrick Gray's Network.HTTP module Network.HTTP is more oriented towards building HTTP clients. HAppS..HTTP is more oriented towards building HTTP servers. Network.HTTP enforces a stronger separation between headers and body. HAppS..HTTP delivers a MIME message back to the app. With infrastructure to enable transparent conversion to and from application datatypes. -Alex- ______________________________________________________________ S. Alexander Jacobson tel:917-770-6565 http://alexjacobson.com

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State Monad
by Derek Elkins 04 Mar '05

04 Mar '05

> Thinking of stacks, I've often wondered if Haskell would be a good > language for implementing a PostScript interpreter. I actually have the beginning of a PostScript interpreter somwhere... And the core of a Joy interpreter is extremely small. It's pretty much 'foldl compose . map interpretWord'. Of course, I implemented a Joy interpreter in the slightly sugared lambda calculus that lambdabot's @eval module supports so... (Crap, I actually want to find it (the PostScript interpreter) now.)

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State Monad
by Sam G. 04 Mar '05

04 Mar '05

I need a Monad to represent an internal stack. I mean I've got a lot of functions which operates on lists and I would not like to pass the list as an argument everytime. Could you help me writing this monad? To start, I just need a + function which will return the sum of the 2 toppest elements of the stack. Thanks in advance, Sam.

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Corba and Haskell
by Maurício 04 Mar '05

04 Mar '05

Hi, Have you guys used any Corba library for Haskell? Which one would you recommend (if there are more than one)? Thanks, Maurício

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haskell DNS resolver w/o using FFI
by S. Alexander Jacobson 03 Mar '05

03 Mar '05

Peter Simons told me that someone has written a DNS resolver in Haskell that doesn't rely on an FFI call. I'd love to look at it if it is available... -Alex- ______________________________________________________________ S. Alexander Jacobson tel:917-770-6565 http://alexjacobson.com

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getting the name of a function for test diagnostic purposes
by Terrence Brannon 03 Mar '05

03 Mar '05

{- I have written a program (below) to run a test suite for a list of functions: [isTotalJunc, isPartialJunc] where each function receives a datum of type ApplyArg whose value slot is one element at a time of the list of types below: [JNone, JOne, JAny, JAll] I therefore must run 8 tests (the cross product of functions and types). Right now, here is the output: *Main> test_total_partial ["fun: (->)input: JNoneoutput: True","fun: (->)input: JOneoutput: False","fun: (->)input: JAnyoutput: False","fun: (->)input: JAlloutput: True","fun: (->)input: JNoneoutput: False","fun: (->)input: JOneoutput: True","fun: (->)input: JAnyoutput: True","fun: (->)input: JAlloutput: False"] -- One problem is that functions do not print as their name. The call to (show f) in showres simply yields (->) -- Another problem is that I cannot manage to separate each string with a carriage return. Any help with these problems is appreciated. -} test_total_partial = let funs = [isTotalJunc, isPartialJunc] types = [JNone, JOne, JAny, JAll] mkdat typ = ApplyArg "somename" (VJunc $ Junc typ emptySet emptySet) False showres f t r = "fun: " ++ (show f) ++ "input: " ++ (show t) ++ "output: " ++ (show r) runtest f t = do { retval <- f (mkdat t); return $ (showres f t retval) } in [ (showres f t (f (mkdat t))) | f <- funs, t <- types ] -- Carter's Compass: I know I'm on the right track when, by deleting something, I'm adding functionality.

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