Re: Bug in users manual, 6.4.2, section on pattern guards
Matthew Cox wrote: One example given in this discussion is: clunky env var1 var1 = case lookup env var1 of Nothing - fail Just val1 - case lookup env var2 of Nothing - fail Just val2 - val1 + val2 where fail = val1 + val2 this needs to be fixed to: clunky env var1 var1 = case lookup env var1 of Nothing - fail Just val1 - case lookup env var2 of Nothing - fail Just val2 - val1 + val2 where fail = var1 + var2(Added for emphasis) I didn't see it myself on the first readthrough, but I was comparing structure between two examples and noticed the discrepency. Let's fix it for correctness' sake. fixed; thanks. Simon ___ Glasgow-haskell-bugs mailing list Glasgow-haskell-bugs@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
Re: Bug in GHC 6.4.1 and 6.4.2
Fritz Henglein wrote: According to a message from GHCi, version 6.4.1 (see below; bug also reproduceable with 6.4.2, though not shown here since it consistently resulted in a core dump without prior message) under Windows XP (fully updated per 2006-07-15), I am herewith reporting what appears to be a bug in GHC. Please see transcript below; the source file in question is included as an attachment. (Lacking both efficient Haskell programming skills and an understanding of the internals of GHC I have refrained from attempting to isolate the bug by reducing the code.) Should there be a simple work-around or something unsafe in my code (though I wouldn't know what: no unsafe operations are used; no polymorphism is present), I would greatly appreciate hearing about it. Thanks, good bug. The problem was: index (minBound::Int16,maxBound) maxBound -1 ie. index for Int16 should have converted to Int *before* doing the subtraction. This is related to another problem (that I think we have a ticket for), namely that the type of index precludes having really large arrays: index :: Ix i = (i,i) - i - Int if the index must fit in an Int, then GHC can't cope with arrays with more than 2^31 elements (on a 32-bit machine), and in general Haskell doesn't allow arrays with more than 2^29 elements. Cheers, Simon ___ Glasgow-haskell-bugs mailing list Glasgow-haskell-bugs@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
Lookup module and package defining x?
Has somene already implemented something like: $ghc-pkg --where-from ParseError package parsec: defining modules: Text.ParserCombinators.Parsec.Error, Text.ParserCombinators.Parsec ? lambdabot @index does what I want, but not with my libs installed only locally.. This might be used by any developement system for easily importing modules.. If not I'll start working on this and I'll post again after needing help ;) or finishing It can't be that hard because there is already ghc-pkg list and ghc --show-iface ... Marc ___ Glasgow-haskell-users mailing list Glasgow-haskell-users@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-users
Re: Lookup module and package defining x?
On Fri, 2006-07-21 at 10:12 +0200, Marc Weber wrote: Has somene already implemented something like: $ghc-pkg --where-from ParseError package parsec: defining modules: Text.ParserCombinators.Parsec.Error, Text.ParserCombinators.Parsec Have you tried Hoogle? http://haskell.org/hoogle/ Your example gives me one result which includes the module name: http://haskell.org/hoogle/?q=ParseError Duncan ___ Glasgow-haskell-users mailing list Glasgow-haskell-users@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-users
Re: Heap Profiling Question
Rich Fought wrote: I'm trying to use heap profiling with +RTS -hc -i1 options and running my program for about 30 seconds. However, I only get around 7 samples with seemingly bogus timetags (i.e. 0.00, 3.69, 3.73, 3.10, 4.05, 4.12). What's going on? I'm running GHC 6.4.2 on Windows (MSYS/MinGW). IIRC the timestamps ignore time spent in GC and time spent sampling the heap, so they measure runtime of the program only. Still, it does look a little strange. Maybe you could send us the output of +RTS -S? Cheers, Simon ___ Glasgow-haskell-users mailing list Glasgow-haskell-users@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-users
Re: Lookup module and package defining x?
$ghc-pkg --where-from ParseError package parsec: defining modules: Text.ParserCombinators.Parsec.Error, Text.ParserCombinators.Parsec Have you tried Hoogle? http://haskell.org/hoogle/ I know it. But I don't know yet which source it takes (haskell - source, haddck html files, ...) ? My purpose: After having found the a function I want to use it without having to search where does it belong to and where does it come from. I want it beeing as up to date as the installed libraries. That's why I thought it might be best to integrate it into ghc? I don't know wether you've ever prorgammed in Java using Eclipse? After using a type you can press C-S-o to update all imports which will give you the choice which one to use if there is more than one opportunity. It would be nice to have this in haskell, too. Do you think it would be better to integrate it in another tool such like lambdabot or hoogle? Marc ___ Glasgow-haskell-users mailing list Glasgow-haskell-users@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-users
Re: Lookup module and package defining x?
Marc Weber [EMAIL PROTECTED] wrote: My purpose: After having found the a function I want to use it without having to search where does it belong to and where does it come from. I want it beeing as up to date as the installed libraries. You can download Hoogle as a command-line tool, and give it your complete installed libraries to index. Then it will be accurate for your own setup. Of course, you would need to manually update it every time you install a new library. That's why I thought it might be best to integrate it into ghc? This kind of tool, though useful, has almost nothing in common with the compiler. Although I suppose it would be useful if Hoogle could read the ghc-pkg file format when indexing all locally-available modules. Regards, Malcolm ___ Glasgow-haskell-users mailing list Glasgow-haskell-users@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-users
Re: Lookup module and package defining x?
Hi, My purpose: After having found the a function I want to use it without having to search where does it belong to and where does it come from. I'm not sure what you are asking for? Where does it come from? Surely thats just the module name - which hoogle easily gives you. If there is some information that hoogle doesn't provide about the location of a module, I'll be happy to add it. I want it beeing as up to date as the installed libraries. That's why I thought it might be best to integrate it into ghc? I want hoogle to always be as up to date as the latest stable GHC, since that should be the one for most people. I am also working on adding libraries, Gtk is already searchable, more will be with hoogle 4. This should cover all the libraries you have installed. Of course, they won't match your versions, they'll be the most up to date ones. If this is a problem feel free to install Hoogle locally, generate hoogle databases using haddock with the -hoogle flag. With a bit of shell script magic you should have everything you need to make something that does what you want. And of course, once you have, please release it back to the world :) Do you think it would be better to integrate it in another tool such like lambdabot or hoogle? If you integrate something with hoogle, then you get it from lambdabot for free, with @hoogle. Thanks Neil ___ Glasgow-haskell-users mailing list Glasgow-haskell-users@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-users
Re: Heap Profiling Question
Simon Marlow wrote: IIRC the timestamps ignore time spent in GC and time spent sampling the heap, so they measure runtime of the program only. So if I have a server that is idle most of the time waiting for requests, the timestamps recorded in the heap profile will not be real time but program execution time? Still, it does look a little strange. Maybe you could send us the output of +RTS -S? AllocCollectLiveGCGC TOT TOT Page Flts bytes bytes bytes user elapuserelap 264424262144 20592 0.00 0.000.030.0100 (Gen: 1) 311540270336 63732 0.00 0.003.845.2500 (Gen: 0) 270304290816102352 0.00 0.003.855.2600 (Gen: 0) 273472270336133644 0.00 0.003.855.2600 (Gen: 0) 314540294912167000 0.00 0.003.905.3100 (Gen: 0) 266356294912212212 0.00 0.003.905.3100 (Gen: 0) 262128331776214120 0.00 0.003.925.3300 (Gen: 0) 262128270336216456 0.00 0.003.925.3300 (Gen: 0) 262128266240218800 0.00 0.003.925.3300 (Gen: 0) 262128266240221140 0.00 0.003.925.3300 (Gen: 0) 262128266240225844 0.00 0.003.925.3300 (Gen: 0) 262128266240231052 0.00 0.003.925.3300 (Gen: 0) 262128266240236516 0.00 0.003.925.3300 (Gen: 0) 262128266240242344 0.00 0.003.925.3400 (Gen: 0) 262144266240248576 0.00 0.003.925.3400 (Gen: 0) 262128266240255212 0.00 0.003.925.3400 (Gen: 0) 262128266240262328 0.00 0.003.925.3400 (Gen: 0) 262128266240270016 0.00 0.003.925.3400 (Gen: 0) 262128266240278620 0.00 0.003.925.3400 (Gen: 0) 262128266240288648 0.01 0.013.945.3500 (Gen: 0) 262128266240300372 0.00 0.003.945.3500 (Gen: 0) 262128266240317000 0.00 0.003.945.3500 (Gen: 0) 262128266240346080 0.00 0.003.945.3500 (Gen: 0) 262128270336348424 0.00 0.003.945.3500 (Gen: 0) 262128266240350760 0.00 0.003.945.3500 (Gen: 0) 262128266240353364 0.00 0.003.945.3600 (Gen: 0) 262128266240358512 0.00 0.003.945.3600 (Gen: 0) 262128266240363748 0.00 0.003.945.3600 (Gen: 0) 262128266240369324 0.00 0.003.945.3600 (Gen: 0) 262128266240375232 0.00 0.003.945.3600 (Gen: 0) 262128266240381528 0.00 0.003.945.3600 (Gen: 0) 262128266240388320 0.00 0.003.945.3600 (Gen: 0) 262128266240395496 0.00 0.003.945.3600 (Gen: 0) 262128266240403424 0.00 0.003.945.3600 (Gen: 0) 262128266240412268 0.00 0.003.945.3600 (Gen: 0) 262128266240422584 0.00 0.003.945.3600 (Gen: 0) 262128266240435088 0.00 0.003.965.3700 (Gen: 0) 262128266240454476 0.00 0.003.965.3700 (Gen: 0) 262224266240477316 0.00 0.003.965.3700 (Gen: 0) 262128270336479676 0.00 0.003.965.3700 (Gen: 0) 262128266240482012 0.00 0.003.965.3800 (Gen: 0) 262128266240485236 0.00 0.003.965.3800 (Gen: 0) 262128266240490364 0.00 0.003.965.3800 (Gen: 0) 262124266240495700 0.00 0.003.965.3800 (Gen: 0) 262128266240501292 0.00 0.003.965.3800 (Gen: 0) 262128266240507344 0.00 0.003.965.3800 (Gen: 0) 262128266240513676 0.00 0.003.965.3800 (Gen: 0) 262128266240520632 0.00 0.003.965.3800 (Gen: 0) 262128266240527924 0.00 0.003.965.3800 (Gen: 0) 262128266240536016 0.00 0.003.965.3800 (Gen: 0) 262128266240545180 0.00 0.003.965.3800 (Gen: 0) 262128266240555808 0.01 0.013.985.3900 (Gen: 0) 262128266240569148 0.00 0.003.985.3900 (Gen: 0) 262128266240593492 0.00 0.003.985.3900 (Gen: 0) 262152266240683760 0.00 0.003.985.3900 (Gen: 0) 262128266240779176 0.00 0.003.985.3900 (Gen: 0) 262128266240874588 0.00 0.00
Re[2]: Lookup module and package defining x?
Hello Marc, Friday, July 21, 2006, 3:21:29 PM, you wrote: I don't know wether you've ever prorgammed in Java using Eclipse? After using a type you can press C-S-o to update all imports which will give you the choice which one to use if there is more than one opportunity. It would be nice to have this in haskell, too. there is EclipseFP plugin which supports some of Eclipse features for haskell users Do you think it would be better to integrate it in another tool such like lambdabot or hoogle? it will be great if Cabal after library installation runs local hoogle to update its information -- Best regards, Bulatmailto:[EMAIL PROTECTED] ___ Glasgow-haskell-users mailing list Glasgow-haskell-users@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-users
Re: Heap Profiling Question
On a separate issue, I can't seem to get the -hcname or -hmname options to work. For instance, profiling with just -hm yields an entry for module Network.HTTP, yet when I try to profile again with -hmNetwork.HTTP, I do not get a heap dump. Is there some special formatting I am missing? Thanks, Rich Rich Fought wrote: I'm trying to use heap profiling with +RTS -hc -i1 options and running my program for about 30 seconds. However, I only get around 7 samples with seemingly bogus timetags (i.e. 0.00, 3.69, 3.73, 3.10, 4.05, 4.12). What's going on? I'm running GHC 6.4.2 on Windows (MSYS/MinGW). Thanks, Rich ___ Glasgow-haskell-users mailing list Glasgow-haskell-users@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-users ___ Glasgow-haskell-users mailing list Glasgow-haskell-users@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-users
regex.h included with GHC 6.4.2
Am I crazy or is there an error in regex.h included with GHC?
On line 110 there appears to be an extraneous or unterminated 'extern C {'
Regards,
Rich
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[Haskell] ANN: monadic probabilistic functional programing
Dear all, the library PFP by Martin Erwig is quite useful for probabilistic calculations. I have extended it to abstract monads, cabal and darcs, confer [1]. I cannot find a licence or legal note on the page of Martin Erwig. Therefore, I can legally only publish a patch. Unfortunatly, darcs does not provide a method to extract patches as far as I know. (Hints are welcomed.) As a result you can download a stripped down version of my darcs repository from [1]. How to create the complete repository is there described, too. [1] http://home.arcor.de/s.ka/haskell/pfp.html Kind regards, -- Stefan Karrmann ___ Haskell mailing list Haskell@haskell.org http://www.haskell.org/mailman/listinfo/haskell
[Haskell] PLAN-X 2007: Call for Papers and Demos
[ Dear all, I'd love to see contributions from the Haskell and FP community to this upcoming edition of PLAN-X! Best wishes, -- Torsten ] Call for Papers and Software Demonstrations P L A N - X 2 0 0 7 Programming Language Techniques for XML An ACM SIGPLAN Workshop colocated with POPL 2007 Nice, France -- January 20, 2007 http://www.plan-x-2007.org/ -- PLAN-X 2007 Aim and Scope The XML data model and its associated languages add interesting twists to programming language practice as well as theory. Just like its four predecessors, the PLAN-X 2007 workshop turns the spotlight on how programming languages can embrace, for example, tree-shaped XML data structures, regular expression types extracted from schema descriptions, very small or large XML instances, queries against XML data, and XML transformations. XML reaches deep into all aspects of language design, type systems, compilers, as well as runtimes and PLAN-X 2007 is THE forum to present and discuss novel research work in this area. We invite contributions -- papers as well as software demonstrations -- from members of the programming language, database, theory, and document processing communities and look forward to a workshop in which this diversity of contributions and attendees leads to lively discussion and a fun event. If you are architecting a software system that fuses programming language and XML technology in interesting and innovative ways, please submit a software demonstration proposal to PLAN-X 2007. The workshop program will feature a special demo session. A two-page description of the accepted software demonstrations will be included in the proceedings. PLAN-X 2007 will be held in cooperation with and just after POPL 2007, the 34th ACM SIGPLAN-SIGACT Symposium on Principles of Programming Languages in the Plaza Hotel in Nice, France, on Januar 20, 2007. -- PLAN-X 2007 Topics of Interest Topics of interest include the following (though interesting and/or innovative papers on all aspects of programming languages for XML are welcome): - Design of programming and query languages for XML - Programming in the XML data model itself (e.g., extending XQuery into a full-fledged programming language) - Formal accounts of XML and its processors (based on logic, automata, variants of lambda calculus, etc.) - Compilers and interpreters for XML-aware languages and optimization techniques - Type systems, schema languages, and other constraints (e.g., keys) for tree-shaped data - Tree automata and transducers - Languages and systems that can cope with XML fragments (messages) or very large XML instances (beyond main-memory size) - Programming language glue between browsers, web services, and databases - Pioneering applications of XML-aware language technology -- Proceedings Accepted submissions will be collected to form the informal PLAN-X 2007 proceedings, to be indexed on Michael Ley's DBLP site and distributed at the workshop. The material may thus be published elsewhere at a later date. -- Paper Submission PLAN-X 2007 calls for contributions relevant to the open list of topics sketched above. We explicitly welcome reports on innovative, off-beat, and ''early stage'' approaches as long as the submission reports on original work not published or submitted elsewhere. - Please format your papers according to the ACM guidelines and SIG proceedings templates available at http://www.acm.org/sigs/pubs/proceed/template.html The mandatory submission file format is PDF. - Papers should not exceed 10 pages in length including references and appendices, but shorter abstracts (of, e.g., 2000 words) often suffice and are acceptable as well. - Software demonstration proposals are limited to 2 pages and should include a sketch of the methods you employ as well as a description of what exactly will be demoed. Details on the PLAN-X 2007 paper submission process will be posted on the workshop web site and mailing lists in due course. -- Important Dates - Paper submission: Sun, Oct 1, 2006 - Notification of acceptance: Thu, Nov 23, 2006 - Camera-ready copy due: Sun, Dec 17, 2006 - Workshop: Sat, Jan 20, 2007 -- PLAN-X 2007 Program Committee - Michael Benedikt(Lucent, USA) - Daniela Florescu(Oracle, USA) - Alain Frisch(INRIA Roquencourt, France) - Giorgio Ghelli, Chair (U Pisa, Italy) - Haruo Hosoya(U Tokyo, Japan) - Anders Møller (U Aarhus, Denmark) - Mukund Raghavachari (IBM T.J. Watson Research Center, USA) - Alan Schmitt(INRIA Rhône-Alpes, France) -
Re: [Haskell] ANN: monadic probabilistic functional programing
On 7/19/06, Stefan Karrmann [EMAIL PROTECTED] wrote: Unfortunatly, darcs does not provide a method to extract patches as far as I know. (Hints are welcomed.) darcs diff and darcs annotate. -- Taral [EMAIL PROTECTED] You can't prove anything. -- Gödel's Incompetence Theorem ___ Haskell mailing list Haskell@haskell.org http://www.haskell.org/mailman/listinfo/haskell
Re: [Haskell] using the ffi with callbacks
On 7/20/06, Evan Martin [EMAIL PROTECTED] wrote: But I also don't quite understand how the typing works out. For example, can you use StablePtr directly with FFI functions, or do they require you casting through Ptr? Yes. You can use any Storable with FFI functions, as far as I know. StablePtr is explicitly designed for this purpose, allowing you to export an object to the FFI while keeping the GC apprised of its use by external code. /* C code, as before but with a typedef for clarity */ typedef void (*Callback)(void*); void register_callback( Callback callback_fcn, void *callback_data, Callback free_fcn); -- importing this function. -- you had: type Callback = StablePtr (Callback, DataStructure)- IO () foreign import ccall register_callback :: FunPtr Callback - -- because mkCallback gives a FunPtr Ptr (Callback, DataStructure) - -- or StablePtr? Callback - -- but here don't we again need a FunPtr? IO () Oh, right. Try: type CallbackData = StablePtr (CallbackData, DataStructure) type Callback = CallbackData - IO () foreign import ccall register_callback :: FunPtr Callback - CallbackData - FunPtr Callback - IO () You get that FunPtr by the import/export trick described by Anatoly or you can just construct the FunPtr in main or an unsafePerformIO CAF. (We need a constructor syntax for top-level objects requiring IO!) -- Taral [EMAIL PROTECTED] You can't prove anything. -- Gödel's Incompetence Theorem ___ Haskell mailing list Haskell@haskell.org http://www.haskell.org/mailman/listinfo/haskell
Re: [Haskell] Package mounting proposal
My 2 cents: Sven Moritz Hallberg (Sun, Jul 16, 2006 at 01:24:43AM +0200): [...] She must specify it somehow. Two possibilities come to mind: 1. Add a field to the package description of foo (v1.4, say) that says I'm backwards-compatible with 1.3. When building, this relation would have to be inspected to see whether any currently installed version of foo satisfies the dependency specified by the mount. 2. Declare a convention for version numbers to carry compatibility information, like the OpenGL standard, for example: If the new version is backwards-compatible, only the minor version number changes. If it isn't, the major version number must be incremented. I prefer 1. The FSF use 2 for its GNU software and others started with it, too. But after a while most of them tend to increase major numbers. E.g. 3.0, 3.11, 95, 98, 2000 Regards, -- Stefan Karrmann If A equals success, then the formula is _A = _X + _Y + _Z. _X is work. _Y is play. _Z is keep your mouth shut. -- Albert Einstein ___ Haskell mailing list Haskell@haskell.org http://www.haskell.org/mailman/listinfo/haskell
Re: [Haskell] ANN: monadic probabilistic functional programing
Dear all, I have renamed all files. Because of this the darcs diff contains *all* source lines. Then it is not only a patch but also the complete original work. Moreover, the patch does not contain a move from or unlink of the old locations. Taral (Fri, Jul 21, 2006 at 11:22:22AM -0500): On 7/19/06, Stefan Karrmann [EMAIL PROTECTED] wrote: Unfortunatly, darcs does not provide a method to extract patches as far as I know. (Hints are welcomed.) darcs diff and darcs annotate. Regards, -- Stefan Karrmann ___ Haskell mailing list Haskell@haskell.org http://www.haskell.org/mailman/listinfo/haskell
Re: [Haskell] ANN: monadic probabilistic functional programing
On Fri, Jul 21, 2006 at 10:26:04PM +0200, Stefan Karrmann wrote: I have renamed all files. Because of this the darcs diff contains *all* source lines. Then it is not only a patch but also the complete original work. Moreover, the patch does not contain a move from or unlink of the old locations. If the original code was already in a darcs repository, you can create a darcs patch bundle by 'darcs send'ing against a repository, which contains only the original patches. You do it like this: $ cd repository-with-your-extensions $ darcs send -o my.patchse original-repository Now if someone has an original repository, he/she can apply your patches in this repository. The patch bundle can still contain parts of the original work as parts of primitive patches. Best regards Tomasz ___ Haskell mailing list Haskell@haskell.org http://www.haskell.org/mailman/listinfo/haskell
Re: [Haskell-cafe] Re: Why is there no splitBy in the list module?
On 2006-07-20 at 18:31BST I wrote: On 2006-07-13 at 10:16BST I wrote: Hooray! I've been waiting to ask Why aren't we asking what laws hold for these operations? Having thought about this for a bit, I've come up with the below. This is intended to give the general idea -- it's not polished code, And already some changes (but all to comments) I'd appreciate comments on the law below. --- lib/split.lhs 2006/07/21 08:54:28 1.1 +++ lib/split.lhs 2006/07/21 09:42:49 @@ -17,10 +17,17 @@ = A Random List Of Words\nOn Lines + I think the relevant law is + (forall x. all (not . p) (map f x)) = + segmentsSatisfying (not . p) . fromParts . mapRight f . parts p + == segmentsSatisfying (not . p) + + In other words, if f doesn't add any not . p elements, + the segments satisfying not . p are unchanged. contiguousParts p l = [a | Right a - parts p l] - so words = contiguousParts Char.isAlphaNum + so words = contiguousParts (not . Char.isSpace) segmentsSatisfying predicate = concat . map dropSeps . parts predicate -- Jón Fairbairn Jon.Fairbairn at cl.cam.ac.uk ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
RE: Re[4]: [Haskell-cafe] REALLY simple STRef examples
| | ps: you successfully going through all the standard Haskell troubles | in | | this area :) seems that making FAQ about using ST monad will be a | | good idea :) | | Indeed. If someone would like to start one, a good place for it would be | GHC's collaborative-documentation Wiki | http://haskell.org/haskellwiki/GHC#Collaborative_documentation | | they are not ghc-specific, afaik Some aspects are -- e.g. the behaviour of higher-rank types. But by all means attach it somewhere else S ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] seq - RTFM?
Hello all, my question is probably dull. So answers to better investigate manual are welcome. Why is this correct? ___ ___ _ / _ \ /\ /\/ __(_) / /_\// /_/ / / | | GHC Interactive, version 6.4.1, for Haskell 98. / /_\\/ __ / /___| | http://www.haskell.org/ghc/ \/\/ /_/\/|_| Type :? for help. Loading package base-1.0 ... linking ... done. Prelude putStr Ahoj\n Ahoj Prelude putStr Ahoj\n `seq` 3+3 6 Prelude :q Leaving GHCi. And not Prelude putStr Ahoj\n Ahoj Prelude putStr Ahoj\n `seq` 3+3 Ahoj 6 ??? Does it have something common with monads or is it a behavior of seq? Thanks, Dusan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] seq - RTFM?
On 21/07/06, Dusan Kolar [EMAIL PROTECTED] wrote: Prelude putStr Ahoj\n Ahoj Prelude putStr Ahoj\n `seq` 3+3 6 Prelude :q Leaving GHCi. And not Prelude putStr Ahoj\n Ahoj Prelude putStr Ahoj\n `seq` 3+3 Ahoj 6 Well, I understand that seq evaluates the first argument. But the result of evaluating putStr is a monadic action. Not execution of that action. Regards, Piotr Kalinowski -- Intelligence is like a river: the deeper it is, the less noise it makes ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] seq - RTFM?
Hello Dusan, The reason why that does not work as you expect it to is because the type of the whole expression is not monadic. Therefore it will basically evaluate the action until it's an action ready to be executed, but not execute it, cause it's not in the IO monad. It's the same as having a list of [putStr a, putStr b]. Until you start placing these actions in the IO monad, they'll just be values. Hope that's somewhat clear Dusan Kolar wrote: Hello all, my question is probably dull. So answers to better investigate manual are welcome. Why is this correct? ___ ___ _ / _ \ /\ /\/ __(_) / /_\// /_/ / / | | GHC Interactive, version 6.4.1, for Haskell 98. / /_\\/ __ / /___| | http://www.haskell.org/ghc/ \/\/ /_/\/|_| Type :? for help. Loading package base-1.0 ... linking ... done. Prelude putStr Ahoj\n Ahoj Prelude putStr Ahoj\n `seq` 3+3 6 Prelude :q Leaving GHCi. And not Prelude putStr Ahoj\n Ahoj Prelude putStr Ahoj\n `seq` 3+3 Ahoj 6 ??? Does it have something common with monads or is it a behavior of seq? Thanks, Dusan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe -- Christophe Poucet Ph.D. Student DESICS - DDT Phone:+32 16 28 87 20 E-mail: Christophe (dot) Poucet (at) imec (dot) be IMEC vzw -- Register of Legal Entities Leuven VAT BE 0425.260.668 -- Kapeldreef 75, B-3001 Leuven, Belgium -- http://www.imec.be IMEC e-mail disclaimer: http://www.imec.be/wwwinter/email-disclaimer.shtml ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Still not dead
Hello As many of you may have noticed I have been away for some months. This has been due to health problems which have unfortunately kept me unable to work on Haskell projects. I am not dead and will be working on resolving the backlog of messages (will probably take a week). I will be slowly back to hacking things when I get everything fixed. - Einar Karttunen ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] HXT - problems with runIOSLA or xread
Hi everybody,
and especially Uwe Schmidt et al.
I ran into some problems trying to process some xml from a string source,
illustrated in the code below. From file, using readDocument, everything works
great though. I've probably missed a finer detail or two in the arrow handling,
or it could be a bug in HXT (if I run the code in ghci, it will crash hard).
Output:
--main.exe
NTree (XTag (QN {namePrefix = , localPart = small, namespaceUri = }) []) [
NTree (XTag (QN {namePrefix = , localPart = xml, namespaceUri = }) []) [],
NTree (XTag (QN {namePrefix = , localPart = example, namespaceUri = }) [])
[]]
--
So it seems that the string gets read, since it shows up as a result from
procString, but I get no output from writeDocument in writeStrDoc. Could anybody
enlighten me?
I'm using GHC 6.5 and HXT 6.0 on Windows XP.
Regards,
/Niklas
---8---
module Main where
import Text.XML.HXT.Arrow
wa = [(a_indent, 1), (a_remove_whitespace, 1)]
main = procString tststr = mapM_ print . snd
procString = runIOSLA writeStrDoc (initialState ())
writeStrDoc = xread writeDocument wa -
tststr = smallxml/example//small
---8---
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Re: Re[4]: [Haskell-cafe] REALLY simple STRef examples
The IO monad hasn't given me too much trouble, but I want to be sure to structure things the way they should be. If I get everything running using IO first and then have type-checking problems with ST, it will be tempting to just slap on an unsafePerformIO and call it good. Sure, it's really doing the same thing anyway, but it just comes out looking like a hack. On 7/20/06, Bulat Ziganshin [EMAIL PROTECTED] wrote: Hello Chad, Friday, July 21, 2006, 12:26:58 AM, you wrote: Ok, I see now why the return is necessary. btw, it may be helpful to read IO inside material. ST monad is not very different from IO monad - it only limited to operations on STRef and STArray, so that it can't have side-effects visible outside of runST statement used to run ST computation ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: ANN: System.FilePath 0.9
Neil Mitchell wrote: I have also added a canonicalPath function, support for spotting file\con as invalid and fixing it, support for \\?\ paths (if you don't know what they are, don't look it up, they are quite painful!) and a few very obscure corner cases which broke some of the properties. I haven't been following this discussion very closely, but this caught my eye. Has anyone pointed out yet that eliminating .. in a FilePath isn't valid in the presence of symbolic links? I vaguely recall that this is why Krasimir's System.FilePath library doesn't include normalisation. Normalisation that just changes separators, removes redundant separators and removes . components is probably ok. I don't really see the point of fullPathWith. Isn't it just combine? I think shortPath is on dodgy ground, given the difficulty with normalising FilePaths, and the fact that paths are not unique in the presence of symlinks. The temporary file stuff is wrong - see System.IO.openTemporaryFile. The only way to reliably create a temporary file is to open it at the same time, otherwise there's a race condition. I have some other issues with naming, and the fact that the library mixes IO and non-IO functions. We should avoid referring to $PATH as the path, since we already have FilePath. eg. spiltPath and getPath are talking about two very different things. Where you use the term Filename, I think it should probably be FilePath. I think we should consistently use a single term, preferably FilePath. Cheers, Simon ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: ANN: System.FilePath 0.9
Hi, I haven't been following this discussion very closely, but this caught my eye. Has anyone pointed out yet that eliminating .. in a FilePath isn't valid in the presence of symbolic links? I vaguely recall that this is why Krasimir's System.FilePath library doesn't include normalisation. Normalisation that just changes separators, removes redundant separators and removes . components is probably ok. Ok, I'll remove this behaviour I don't really see the point of fullPathWith. Isn't it just combine? It also applies normalise to the result, although I'm not sure thats a particularly useful thing to do. I'll think about this. I think shortPath is on dodgy ground, given the difficulty with normalising FilePaths, and the fact that paths are not unique in the presence of symlinks. I think this is still a useful thing, but I'll think harder about it in relation to symlinks, and figure out what properties it should have. The temporary file stuff is wrong - see System.IO.openTemporaryFile. The only way to reliably create a temporary file is to open it at the same time, otherwise there's a race condition. Looking at it again, I'm not sure that the temporary operations belong in this module. Ditto for the directory operations. It would be handy if the directory operations (particularly ensureDirectory) were somewhere else in the standard libraries though. I have some other issues with naming, and the fact that the library mixes IO and non-IO functions. I think this is unavoidable, I tried to make as many functions as possible pure, but where the filesystem must be consulted they have to be IO based. For example canonicalPath probably belongs in this module, but has to be IO based. We should avoid referring to $PATH as the path, since we already have FilePath. Agreed, but I couldn't come up with a better name, if anyone has any suggestions. Where you use the term Filename, I think it should probably be FilePath. I think we should consistently use a single term, preferably FilePath. I have tried to consistently use FilePath as a path to a file, and filename as the actual name once you get there. For example: /usr/bin/ghc Has a FilePath of /usr/bin/ghc and a FileName of ghc. That distinction seems more logical to me, but if everyone thinks otherwise I'm happy to change it. Thanks Neil ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] REALLY simple STRef examples
Not totally relevant to what the discussion has evolved to, but I wrote a factorial function using STRefs (in the spirit of the Evolution of a Haskell programmer) and I think it qualifies as a really simple example. Code follows: import Data.STRef import Control.Monad.ST foreach :: (Monad m) = [a] - (a - m b) - m () foreach = flip mapM_ -- Bryn Keller's foreach, but with type restrictions fac :: (Num a, Enum a) = a - a fac n = runST (fac' n) fac':: (Num a, Enum a) = a - ST s a fac' n = dor - newSTRef 1 foreach [1..n] (\x - modifySTRef r (*x)) x - readSTRef r return x Chad Scherrer wrote: The IO monad hasn't given me too much trouble, but I want to be sure to structure things the way they should be. If I get everything running using IO first and then have type-checking problems with ST, it will be tempting to just slap on an unsafePerformIO and call it good. Sure, it's really doing the same thing anyway, but it just comes out looking like a hack. On 7/20/06, Bulat Ziganshin [EMAIL PROTECTED] wrote: Hello Chad, Friday, July 21, 2006, 12:26:58 AM, you wrote: Ok, I see now why the return is necessary. btw, it may be helpful to read IO inside material. ST monad is not very different from IO monad - it only limited to operations on STRef and STArray, so that it can't have side-effects visible outside of runST statement used to run ST computation ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: ANN: System.FilePath 0.9
Neil Mitchell writes: We should avoid referring to $PATH as the path, since we already have FilePath. Agreed, but I couldn't come up with a better name, if anyone has any suggestions. searchPath? -- David Menendez [EMAIL PROTECTED] http://www.eyrie.org/~zednenem/ ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] incoherent instance selection when it should be still coherent
The following pain is sort of ghc (6.4.2) specific.
(The same behavior is achievable with hugs -98 +O which is Ok in so far
that +O (as opposed to +o) is not strongly supposed to be coherent.)
Note the following GHC options preceding the code.
They do not contain -fallow-incoherent-instances.
{-# OPTIONS -fglasgow-exts #-}
{-# OPTIONS -fallow-undecidable-instances #-}
{-# OPTIONS -fallow-overlapping-instances #-}
-- A single parameter class with two silly instances
class Foo x where foo :: x - (); foo = const ()
instance Foo ()
instance Foo Bool
-- A two-parameter class with a generic and a non-generic instance
class (Foo x, Foo y) = Bar x y where bar :: x - y - String
instance (Foo x, Foo y) = Bar x y where bar _ _ = generic instance
instance Foo z = Bar () z where bar _ _ = non-generic instance
-- An existential wrapper around foos
data Wrap = forall x. Foo x = Wrap x
-- A wrapper-based variation on the type-class member bar
uuh :: Wrap - Wrap - String
uuh (Wrap x) (Wrap y) = bar x y
-- Let's try all unwrapped and wrapped combinations of bar and uuh
t1 = ()
t2 = True
w1 = Wrap t1
w2 = Wrap t2
main = do
print $ bar t1 t1
print $ uuh w1 w1 -- uuh!
print $ bar t1 t2
print $ uuh w1 w2 -- uuh!
print $ bar t2 t1
print $ uuh w2 w1
print $ bar t2 t2
print $ uuh w2 w2
We get:
{-
non-generic instance
generic instance
non-generic instance
generic instance
generic instance
generic instance
generic instance
generic instance
-}
This means that the generic instance is consistently chosen by uuh.
This is clearly incoherent.
I would also complain that uuh type-checks in the first place.
Opinions?
Regards,
Ralf
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Re: [Haskell-cafe] REALLY simple STRef examples
On 7/21/06, S C Kuo [EMAIL PROTECTED] wrote: Not totally relevant to what the discussion has evolved to, but I wrote a factorial function using STRefs (in the spirit of the Evolution of a Haskell programmer) and I think it qualifies as a really simple example. Code follows: import Data.STRef import Control.Monad.ST foreach :: (Monad m) = [a] - (a - m b) - m () foreach = flip mapM_ -- Bryn Keller's foreach, but with type restrictions fac :: (Num a, Enum a) = a - a fac n = runST (fac' n) fac':: (Num a, Enum a) = a - ST s a fac' n = dor - newSTRef 1 foreach [1..n] (\x - modifySTRef r (*x)) x - readSTRef r return x Forgive me for not understanding, but I was hoping you would explain a choice you made in your code. Why did you define foreach and then use foreach [1..n] (\x - modifySTRef r (*x)) Instead of simply using mapM_ (\x - modifySTRef r (*x)) [1..n] ? I tried it out in GHCi, and it worked fine, and I have seen code that has been defined as a flip to take advantage of partial application. But your code doesn't seem to take advantage of partial application, so why did you define 'foreach' and then use it instead of using 'mapM_'? I am just curious, and have always been interested in reasons behind coding style. Bryan Burgers ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
