[Haskell-cafe] haskell flickr bindings: invalid signature when uploading
I've mailed the maintainer of the flickr api package but thought I would see if other people had this experience too. Google doesn't reveal many people using this package as far as I can tell. In short, authentication works fine but uploading images fails with this message. This happens with the included examples/Uploader.hs as well as my own code. toRequest: POST request contains 1 files; unable to represent as query string Defaulting to multiform/form-data instead Flickr error: Code: 96 Type: Flickr API error Details: Invalid signature I haven't had a chance to dive deeper into this yet, but any advice gratefully received. Cheers, D -- Dougal Stanton dou...@dougalstanton.net // http://www.dougalstanton.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] haskell flickr bindings: invalid signature when uploading
Yes, that seems to be the reasonable assumption though I can't find any good changelogs for the api. Further investigation will have to wait until after the weekend :-) Cheers, D On Fri, Dec 10, 2010 at 12:51 PM, Stuart Dootson stuart.doot...@gmail.com wrote: On 10 Dec 2010, at 12:39 PM, Dougal Stanton dou...@dougalstanton.net wrote: I've mailed the maintainer of the flickr api package but thought I would see if other people had this experience too. Google doesn't reveal many people using this package as far as I can tell. In short, authentication works fine but uploading images fails with this message. This happens with the included examples/Uploader.hs as well as my own code. toRequest: POST request contains 1 files; unable to represent as query string Defaulting to multiform/form-data instead Flickr error: Code: 96 Type: Flickr API error Details: Invalid signature I haven't had a chance to dive deeper into this yet, but any advice gratefully received. Cheers, D -- Dougal Stanton dou...@dougalstanton.net // http://www.dougalstanton.net That wouldn't surprise me - I have a suspicion the Flickr API has changed since hs-flickr was released - certainly there are issues with things like getting full comment information out, for which I've made some mods within a local copy of hs-flickr, with a mind to push them sometime. Stuart Dootson -- Dougal Stanton dou...@dougalstanton.net // http://www.dougalstanton.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] who's in charge?
2010/10/27 Ivan Lazar Miljenovic ivan.miljeno...@gmail.com: 2010/10/27 Günther Schmidt gue.schm...@web.de: Hi all, this may be an odd question to some, but I think it's actually quite an un-extraordinary one. Who's in charge? Of Haskell I mean. If there was some alien from Planet Java to land on Planet Haskell and demand to be taken to our leader, whom would we take him to? The Haskell' committee? They're just figureheads for a shadowy cabal :-D -- Dougal Stanton dou...@dougalstanton.net // http://www.dougalstanton.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Ed Lambda: Functional programming meetup in Edinburgh
Looks good! I shall try to make it along. I'll have just come from my SICP study group at that point so will want some statically typed chat to soothe the pain :-) D On Mon, Aug 30, 2010 at 9:00 PM, Ollie Saunders oliver.saund...@gmail.com wrote: Hi guys, I'm running a meetup for functional programming in Edinburgh. The first one will be on the 13th of September at Malone's Irish Bar (14 Forrest Road) and will continue every 2nd monday of each month. For the first meetup I think we'll just be having a chat and getting to know each other but I hope to be able to expand it to talks and coding dojos once we have some regular numbers. For more details: http://meetup.com/ed-lambda/ And we're on Twitter: http://twitter.com/ed_lambda ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe -- Dougal Stanton dou...@dougalstanton.net // http://www.dougalstanton.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] gd on Win32
On Fri, Jul 2, 2010 at 8:34 PM, Christopher Done chrisd...@googlemail.com wrote: That sounds like a good idea. I've setup a repo, I've merged in the latest work I did on it, and I've just updated it to be latest Prelude/base and to comply with -Wall. I'm just going to make it consistent with tibbe's style guide[1] before we start patching it for feature updates, so that we're singing from the same hymn sheet and then I'll let you you here. The Github repo is here: http://github.com/chrisdone/gd Excellent news! I submitted some patches to the maintainer a while back but never heard any response, positive or negative. My changes were a subset of what you have on github now. It's great to see it being cared for again! Cheers, D -- Dougal Stanton dou...@dougalstanton.net // http://www.dougalstanton.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] [Newbie] What to improve in my code
On Mon, Jul 19, 2010 at 9:24 AM, David Virebayre dav.vire+hask...@gmail.com wrote: A minor point: instead of removing the punctuation, you maybe should convert it to whitespace. Otherwise in texts like there was a quick,brown fox (notice the missing space after the comma) you'll have the word quickbrown instead of 2 words quick and brown. If you remove punctuation you - run the risk of joining two valid words into one invalid word: quick,brown - quickbrown - run the risk of converting one word into a different word: can't - cant won't - wont If you split at punctuation you create more semi-words: can't - can, t shouldn't - shouldn t It might be better regarding in-word apostrophes as letters in this case? -- Dougal Stanton dou...@dougalstanton.net // http://www.dougalstanton.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: cabal: other-modules
On Thu, Apr 15, 2010 at 1:49 PM, Ivan Lazar Miljenovic ivan.miljeno...@gmail.com wrote: Johannes Waldmann waldm...@imn.htwk-leipzig.de writes: What happened was this: I still don't see why this other-modules is needed. Ok, I understand the technical reason that cabal does not do dependency analysis but morally, it should? Why are people suddenly using the term morally when they mean why doesn't this do what I think it should? None of its definitions seem to match what you mean: http://wordnetweb.princeton.edu/perl/webwn?s=moral The proper use of words isn't dictated by what is found in small dictionaries but by the speakers of the language. Also I would caution against the judgement 'sudden' if you haven't done a corpus check: the recency illusion can be a real pain. 'Morally' seems just the perfect word for this occasion --- concerned with right or proper conduct. In this case, potential discrepancies between the files that cabal 'knows' about when issuing different commands; or the sense of deceit when it 'appears' to work only for faults to appear further down the line. I would guess this is just something we have to live with if cabal can't be expected to include its own parser dependency chaser. Documentation is always a good first step though :-) Cheers, D ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] developing against privately patched libraries, and cabal
On Tue, Mar 23, 2010 at 10:00 AM, Roel van Dijk vandijk.r...@gmail.com wrote:
The documentation for Data.Version might be insightful:
http://haskell.org/ghc/docs/latest/html/libraries/base-4.2.0.0/Data-Version.html
If Cabal uses the parseVersion function to parse versions then the
following version is valid: 1.2.3-a-b-c. If should result in this
value:
Version {versionBranch = [1,2,3], versionTags = [a, b, c]}
But I don't know if Cabal allows you to depend on such a version.
This post has an answer, but not one that makes me very happy ;-)
http://www.mail-archive.com/cabal-de...@haskell.org/msg05955.html
We've not yet removed tag from the parser for backwards compatibility.
Clearly what we should do is add a big warning (or simply error) that
such tags are no longer supported.
I hope in time to get Data.Version changed to eliminate the tags
entirely. (Duncan Coutts)
I guess it's too easy to abuse (says he who was planning to abuse it)
but it's sad that there isn't something I can easily use in its place.
At the moment renaming the package is serving my purpose.
Cheers,
D
--
Dougal Stanton
dou...@dougalstanton.net // http://www.dougalstanton.net
___
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Hackape package lackage
Hackage seems to be down again. $ cabal update Downloading package list from server 'http://hackage.haskell.org/packages/archive' ^Ccabal: interrupted $ ping -c3 hackage.haskell.org PING abbot.galois.com (69.30.63.204) 56(84) bytes of data. --- abbot.galois.com ping statistics --- 3 packets transmitted, 0 received, 100% packet loss, time 2012ms ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] developing against privately patched libraries, and cabal
If you're making local changes against a library you don't own (with the ultimate intention of sending those changes back upstream to the library maintainer) it makes sense change the version number to avoid clashes with the canonical version of the library. Of course, it's easy to lose track and end up publishing your own program against a non-existent (outside your hard disk) version of the library. I'd like to make it very obvious, both in mypogram.cabal and library.cabal that one is a patched copy and the other has to be compiled against a patched copy. Does cabal provide any way of marking a version private? I thought initially to just mark the version field in the patched library as X.y-dougal and enforce my program to compile against that, but it doesn't seem to recognise the -dougal suffix there. Thoughts? D -- Dougal Stanton dou...@dougalstanton.net // http://www.dougalstanton.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] developing against privately patched libraries, and cabal
On Sun, Mar 21, 2010 at 5:15 PM, Leon Smith leon.p.sm...@gmail.com wrote: As somebody who's hacked on cabal-install a bit (but don't have a worthwhile patch to contribute (yet?)), I can tell you that versions support a tag structure, at least internally, but I haven't seen a non-empty tags field and don't know how to make the tags field non-empty. For that I'd have to go source-code diving again. http://www.haskell.org/ghc/docs/latest/html/libraries/Cabal-1.8.0.2/Distribution-Version.html That seems just the kind of thing that could be co-opted to my purposes, but as you say the cabal file format doesn't seem to mention how I'd go about setting my tag field. Trying Tag: dougal1 didn't work, as I suspected ;-) In the mean time I will try Stephen Tetley's approach of renaming the package instead of the version. Cheers, D -- Dougal Stanton dou...@dougalstanton.net // http://www.dougalstanton.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] What is the meaning of tilde (~) symbol
And, I've search the meaning of the symbol ~, but I've found nothing about this (note that's not easy to search ~ on google ...) Searching for haskell tilde produces a lot of results and they're all relevant (on the first page at least). D ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Is Haskell a Fanatic?
On Fri, Dec 4, 2009 at 6:36 AM, Evan Laforge qdun...@gmail.com wrote: I'd just like to point out or reiterate the odd rise in trolling and the recent announcements of haskell-2010... Just wait until haskell-2012 is announced with nonexistential aka eschatological types spelled notany a. World. It evaluates to a new form of bottom that blackholes the entire world... I hear prototypes are already being used at the LHC for this very purpose. Well-typed doomsday machines can't go wrong ;-) D -- Dougal Stanton dou...@dougalstanton.net // http://www.dougalstanton.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Typefuck: Brainfuck in the type system
On Thu, Nov 19, 2009 at 10:47 AM, Cristiano Paris fr...@theshire.org wrote: On Mon, Nov 16, 2009 at 6:26 PM, Gwern Branwen gwe...@gmail.com wrote: ... Too late: ... http://hackage.haskell.org/package/loli What's the point with loli? Mrs Lopsided has all the loli. D -- Dougal Stanton dou...@dougalstanton.net // http://www.dougalstanton.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] How to use bracket properly ?
On Mon, Oct 19, 2009 at 9:18 AM, Ketil Malde ke...@malde.org wrote:
zaxis z_a...@163.com writes:
winSSQ count noRed noBlue = do
let yesRed = [1..33] \\ noRed
let yesBlue = [1..16] \\ noBlue
bracket (openFile ssqNum.txt WriteMode) (hClose) (\hd1 - pickSSQ
count yesRed yesBlue hd1)
It works very well. However, as i am used to C style so i want convert it
into
winSSQ count noRed noBlue = do {
let yesRed = [1..33] \\ noRed;
^^^ ^
Didn't you just comment out your semicolons?
Hi Ketil,
That's the first thing I thought when I read this code, then I
realised those aren't comment delimiters in Haskell! :-)
D
--
Dougal Stanton
dou...@dougalstanton.net // http://www.dougalstanton.net
___
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Hackage down
Has not been responding for at least the last 12 hours. Is there somewhere to look for status reports on sysadmin details like this, so we can tell if - it's a scheduled down time - it's a problem but the admins know about it - etc etc. D -- Dougal Stanton dou...@dougalstanton.net // http://www.dougalstanton.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Examples/docs for simulated annealing bindings
I found the HsASA library [1] on Hackage, but there's no documentation and it's not particularly intuitive. I can't see any obvious way of choosing initial config or generating new configurations. Google reveals no one using it. Does anyone have ideas? [1]: http://hackage.haskell.org/package/HsASA-0.1 Cheers, D -- Dougal Stanton dou...@dougalstanton.net // http://www.dougalstanton.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Debugging Haskell code
On Sun, Sep 27, 2009 at 9:17 PM, Paul Moore p.f.mo...@gmail.com wrote: That's odd, it seems to be saying it's not installed at all! Hmm, no - I did a cabal install --user (because Vista doesn't let me do site-wide installs), looks like cabal list doesn't pick up user installs. Hmm, cabal install mersenne-random --user didn't do anything, but cabal install mersenne-random --user --reinstall did reinstall it, and now it seems to work. To find out what GHC picks up automatically: $ ghc-pkg list /home/dougal/lib/ghc-6.10.3/./package.conf: Cabal-1.6.0.3, HUnit-1.2.0.3, QuickCheck-1.2.0.0, array-0.2.0.0, base-3.0.3.1, base-4.1.0.0, bytestring-0.9.1.4, containers-0.2.0.1, directory-1.0.0.3, (dph-base-0.3), (dph-par-0.3), (dph-prim-interface-0.3), (dph-prim-par-0.3), (dph-prim-seq-0.3), (dph-seq-0.3), extensible-exceptions-0.1.1.0, filepath-1.1.0.2, (ghc-6.10.3), ghc-prim-0.1.0.0, haddock-2.4.2, haskell-src-1.0.1.3, haskell98-1.0.1.0, hpc-0.5.0.3, html-1.0.1.2, integer-0.1.0.1, mtl-1.1.0.2, network-2.2.1, old-locale-1.0.0.1, old-time-1.0.0.2, packedstring-0.1.0.1, parallel-1.1.0.1, parsec-2.1.0.1, pretty-1.0.1.0, process-1.0.1.1, random-1.0.0.1, regex-base-0.72.0.2, regex-compat-0.71.0.1, regex-posix-0.72.0.3, rts-1.0, stm-2.1.1.2, syb-0.1.0.1, template-haskell-2.3.0.1, time-1.1.3, unix-2.3.2.0, xhtml-3000.2.0.1 /home/dougal/.ghc/i386-linux-6.10.3/package.conf: HTTP-4000.0.4, X11-1.4.5, X11-xft-0.3, benchpress-0.2.2.3, cairo-0.10.1, colour-2.3.0, cpphs-1.9, darcs-2.2.1, data-default-0.2, diagrams-0.2, gd-3000.4.0, gio-0.10.1, glib-0.10.1, gtk-0.10.1, hashed-storage-0.3.7, haskeline-0.6.1.6, haskell-src-exts-1.1.4, hscolour-1.15, mmap-0.4.1, soegtk-0.10.1, split-0.1.1, svgcairo-0.10.1, tagsoup-0.6, terminfo-0.2.2.1, terminfo-0.3.0.2, uniplate-1.2.0.3, utf8-string-0.3.4, xmonad-0.8.1, xmonad-contrib-0.8.1, zlib-0.5.0.0, zlib-0.5.2.0 You should get everything hanging about, installed system-wide or in your home directory. I assume this works much the same for Windows. D ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Edinburgh Hackathon (Hac7) summary
It's been nearly a month now since the Edinburgh Hackathon (29 30 August), organised to coincide with the convergence of Haskellers arriving for the ICFP. My apologies for this very late summary! Eric Kow was the driving force behind this Hackathon, though I agreed to help out locally because I live in Edinburgh. We had trouble organising a good venue through a combination of university holidays and Edinburgh International Festival. We spent the first day camping out in a cafe. On the second day Graeme Hutton arranged for us to use an empty room in the bowels of the ICFP venue. If I remember well the first day was heavily Darcs-oriented, and there were interesting conversations on version control representation, conflicts, and the future of Darcs over breakfast. The staff at Henderson's Restaurant didn't seem to mind our impromptu geeky enclave, and we kept buying coffee to pay for our wifi usage. I'll let the other Haskellers explain in their own words what they were up to for the rest of the time. Maybe some of them have updates on where these projects have gone since then? At the hackathon I started working on a small extension to the GHCi debugger. The goal of the extension is to allow the debugger to show the term representation of thunks where possible. Presently, to find out the value of a thunk in the debugger you must force its evaluation. However, this is not always desirable, especially if the thunk contains breakpoints, or if it diverges. In some cases it ought to be possible to extract source code information from a thunk and show that to the user. I didn't get very far in the implementation because I spent most of the time re-learning how the term printer in the debugger works (and chatting to other people). -- Bernie Pope I was continuing to work on my camp correctness proofs. In particular, investigating how best to handle symmetric lemmas, and refactoring the existing definitions and proofs. -- Ian Lynagh I worked on fixing Solaris/SPARC port of GHC. It turned out to be a tedious header file related issue, not very interesting. -- Ben Lippmeier I worked on the formlets (again), I released a version that doesn't add any functionality, it only solves a bug. -- Chris Eidhof I worked on a feature to let darcs users more conveniently upgrade to the hashed repository format. I also had lots of interesting discussions with darcs users and hackers :-) -- Eric Kow I worked on analysing some darcs performance problems, fixing a couple of GHC bugs, and some discussion about packages. -- Simon Marlow I (along with Benedikt Huber) worked on adding a 'cabal init' command which automates much of the work of cabalising a project (creating a .cabal file, a Setup.hs file, a LICENSE file, etc). It's not quite done yet but should be finding its way into the cabal-install HEAD soon! -- Brent Yorgey I worked on the new hackage-server a bit. darcs get http://code.haskell.org/hackage-server/ live instance at http://sparky.haskell.org:8080/; -- Duncan Coutts Thanks everyone who took part and who supplied an elegant summary of their work that weekend. I hope you all had a good time! Cheers, D -- Dougal Stanton dou...@dougalstanton.net // http://www.dougalstanton.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Edinburgh Hackathon round-up
Hello Haskellers, On Saturday Sunday (28th 29th August) we held a Hackathon in Edinburgh, before the ICFP got fully underway. If you were there, thank you for coming. We'll be writing a summary of what happened soon, and we'd love to hear what you did. If you started a new project or fixed some insidious bug, identified a major bottleneck or just enriched the testing structure around your chosen project, it would be great to know. Just a line or two is all we need! I am hoping that everyone who attended will see this message, as they must have seen Eric's original advertising emails. But please pass this message along if you know there's someone we missed. Cheers, Dougal -- Dougal Stanton dou...@dougalstanton.net // http://www.dougalstanton.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] is closing a class this easy?
On Fri, Jul 17, 2009 at 4:38 PM, Conor McBrideco...@strictlypositive.org wrote: class Private x where public :: (forall x. Public x = x - y) - y public f = f Pike data Pike = Pike instance Private Pike instance Public Pike -- But if I don't tell 'em Pike, I've ensured that blah can only be used in the argument to public. Well I appreciated this bit even if no-one else did! :-) Also, that's a nifty trick if it works! D ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Haskell Zippers on Wikibooks: teasing! :)
On Thu, Jul 16, 2009 at 12:11 PM, Heinrich Apfelmusapfel...@quantentunnel.de wrote: Generic Programming: An introduction http://www.cse.chalmers.se/~patrikj/poly/afp98/ It's a bit verbose at times, but you only need the first few chapters to get an idea about polynomial functors (sums and pairs) and mu . Thanks, that's a really nice introduction, which seems to be at just my level for the moment! :-) D ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Colour tutorial (Was: AC-Vector, AC-Colour and AC-EasyRaster-GTK)
On Fri, Jul 10, 2009 at 6:42 AM, rocon...@theorem.ca wrote: On Thu, 9 Jul 2009, rocon...@theorem.ca wrote: You can use by lib without worrying about the CIE. You can use my library without ever importing or using the word CIE. However, the CIE stuff is there for those who need it. Perhaps I (maybe with some help) need to make a tutorial on the haskell wiki to try to make it less intimidating. Okay, I threw together a quick introduction at http://www.haskell.org/haskellwiki/Colour. Any changes, comments, corrections, and addtions are welcome. It's a wiki! Excellent! I admit to being Quite Baffled by the new terminology when I tried using this library a few months ago. Spent a lot of time on WP trying to find out what everything was! Even something as simple as stating yes, just use Colour Double makes the library seem a lot easier to plumb in to other things. A couple of notes: Section 4.2: Out of gamut channels be clamped to either to the range 0 to 255 -- some kind of mix-up here Section 5: Note that\n\nOne should avoid dissolving has a spurious line break, or an unfinished sentence. Cheers, D -- Dougal Stanton dou...@dougalstanton.net // http://www.dougalstanton.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Monoid wants a (++) equivalent
On Tue, Jun 30, 2009 at 11:39 PM, John Meachamj...@repetae.net wrote: (+) seems to imply to me that the operator is non-associative. Something like () or (+) would be better. It's too similar to the applicative (*), and implies all sorts of things like different types of the two arguments and so on. D -- Dougal Stanton dou...@dougalstanton.net // http://www.dougalstanton.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Edinburgh Haskell users meeting this afternoon
Hello Haskell users If you're in the Edinburgh (Scotland!) area and interested in Haskell we may have just the thing for you. I will be meeting one other Haskell Cafe list member at Doctor's pub at 4pm this afternoon (Sunday 21 June). This could be the start of something bigger, so if you're interested in Haskell please drop in and swell the numbers. The conversation will probably be about some of the basics - what is currying? what are typeclasses? what does the deriving keyword do? - so don't feel nervous about being out of your depth! If I can get a table, I will try to display a copy of Hudak's _Haskell School of Expression_ prominently. Please come up and say hello, or fire me back a note if you can't make it but are still interested in making this a regular meeting. Don't be shy about joining us if you're available though! Thanks everyone! Dougal -- Dougal Stanton dou...@dougalstanton.net // http://www.dougalstanton.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Haskell Meetup groups in Glasgow
On Sat, Jun 13, 2009 at 5:09 AM, A Smithasmith9...@gmail.com wrote: Do any Haskell Meetup groups exist in or around Glasgow, an informal get-to-gether in a pub,cafe or wherever ? I'm in Edinburgh, and on my own have been desperately trying to rewire my brain from Perl to Haskell without much success for most of this year. I posted the meetup group question a few weeks ago for Edinburgh but got no response. Sorry, I didn't see your Edinburgh message. I am also in Edinburgh and though I don't know of any Haskell meet-ups I don't think it would be hard to get critical mass for one. Edinburgh Uni teaches it to the first years (AFAIK), Philip Wadler works here, and the ICFP and Haskell Symposium are going to be held here later in the year. There must be more than just the two of us! :-) Cheers, D -- Dougal Stanton dou...@dougalstanton.net // http://www.dougalstanton.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] I have forgotten .. my bad
On Fri, May 15, 2009 at 5:30 AM, Vasili I. Galchin vigalc...@gmail.com wrote: Hello, darcs get --init ?? I want to pull down Data.FiniteMap. I have forgotten the path to Hackage .. I tried sudo darcs get http://hackage.haskell.org/ Data.FiniteMap [sudo] password for vigalchin: Invalid repository: http://hackage.haskell.org darcs failed: Failed to download URL http://hackage.haskell.org/_darcs/inventory : HTTP error (404?) ?? Obviously the code I am cabalizing needs to be upgraded(i.e. not using deprecated packages) but first I want it to build! If you want to install something from Hackage, use $ cabal install foo If you want to grab the source $ darcs get --partial path/to/repo (Omit the --partial flag if you want the full source tree, but if you're not intending to do serious work on the source it's probably not worth it.) From the error message above you appear to be darcs getting the root directory of the hackage server, which isn't a valid repository. Cheers, D -- Dougal Stanton dou...@dougalstanton.net // http://www.dougalstanton.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: ANN: #haskell-in-depth IRC channel
On Wed, Feb 4, 2009 at 5:32 AM, Benjamin L. Russell dekudekup...@yahoo.com wrote: If neither #haskell nor #haskell-in-depth is appropriate, perhaps they would feel more comfortable in a Haskell-beginners-specific channel? The danger with that is the only people who go there are beginners looking for advice. Without advisers also, it would quickly wither. How has the beginners' mailing list worked out, in this regard? At least with a ML it's possible to set aside some part of the day to answering questions... the same is not really possible for 5-hour-old conversations on IRC. Cheers, D ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] cabal list can't find Glob.cabal file?
On Mon, Feb 2, 2009 at 12:01 AM, Duncan Coutts duncan.cou...@worc.ox.ac.uk wrote: The solution is to upgrade: $ cabal install cabal-install $ cabal --version cabal-install version 0.6.0 using version 1.6.0.1 of the Cabal library Yes, this was the problem, despite me upgrading cabal-install before mailing the list. Alas, an old cabal binary was being picked up from /usr/local/bin. Cheers for the help, D ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] cabal list can't find Glob.cabal file?
I get a curious message when trying to run 'cabal list': $ cabal list omit some lines... .. Latest version available: 0.3 Category: Network Synopsis: Pure bindings for the MaxMind IP database. License: OtherLicense cabal: Couldn't read cabal file ./Glob/0.1/Glob.cabal Any ideas? As far as Hackage and the local index are concerned, 0.1 isn't even a recent version of Glob. Why should it be looking for the file? cabal-install version 0.5.1 using version 1.4.0.1 of the Cabal library -- Dougal Stanton dou...@dougalstanton.net // http://www.dougalstanton.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Comments from OCaml Hacker Brian Hurt
On Tue, Jan 20, 2009 at 3:42 PM, Heinrich Apfelmus apfel...@quantentunnel.de wrote: Let me explain this monoid magic, albeit not in this message which would become far too long, but at http://apfelmus.nfshost.com/monoid-fingertree.html That is a very nice summary! I did my own investigation of fingertrees recently [1] and also came to the conclusion that the function names for Monoid really are the ugliest, impractical things for such a beautiful, simple concept. Ah, if only we could go back in time :-) [1]: http://www.dougalstanton.net/blog/index.php/2008/12/12/a-brief-look-at-fingertrees/ Cheers, D ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Comments from OCaml Hacker Brian Hurt
On Thu, Jan 15, 2009 at 11:54 PM, ChrisK hask...@list.mightyreason.com wrote: So the original article, which coined 'Appendable', did so without much thought in the middle of a long post. But it does show the thinking was about collections and there is one ONE instance of Monoid at http://www.haskell.org/ghc/docs/latest/html/libraries/base/Data-Monoid.html#t%3AMonoid that is about a collection (Monoid ([] a)) that has a split operation. The blind man at the back takes firm hold of the tail and says, But why do we need to call it an *elephant*? No-one knows what that is. Everyone knows what a rope is, so we should just call it a rope. And that is how the elephant came to be labelled a rope in all the guide books. :-) Cheers, D ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Comments from OCaml Hacker Brian Hurt
On Fri, Jan 16, 2009 at 1:23 PM, Philippa Cowderoy fli...@flippac.org wrote: On Thu, 15 Jan 2009, Lennart Augustsson wrote: If I see Monoid I know what it is, if I didn't know I could just look on Wikipedia. And if you're a typical programmer who is now learning Haskell, this will likely make you want to run screaming and definitely be hard to understand. We at least need a description that's aimed at people who probably don't consider themselves any flavour of mathematician, however amateur. One that, while giving the definition, concentrates significantly on intuition. Wikibooks has a patchy book on Abstract Algebra which seemed quite friendly to me (a non-mathematician and amateur FPer). I take it for granted there will be parts I don't understand but if I just continue to spot instances in the wild where they come up then it slowly becomes obvious. Collecting examples of concrete monoids is fairly easy fi you read some of the popular Haskell projects: Xmonad, Cabal, etc. I honestly don't see what all the fuss is about. No one's arguing that more documentation is a bad thing. But some people seem to think the mere existence of (a) technical terms or (b) technical terms not invented by programmers are an affront. Cheers, D ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] some ideas for Haskell', from Python
On Wed, Jan 14, 2009 at 3:12 PM, Neil Mitchell ndmitch...@gmail.com wrote: 2) In Python it is possible to import modules inside a function. In Haskell something like: joinPath' root name = joinPath [root, name] importing System.FilePath (joinPath) Looks a bit ugly, but kind of useful. I'd make the syntax: joinPath' root name = joinPath [root,name] where import System.FilePath(joinPath) It does mean you need to read an entire file to see what functions it imports, but perhaps that is the way it should be. I could also imagine a syntax: joinPath' root name = import.System.FilePath.joinPath [root,name] i.e. doing an import and use at the same time. This can be done with a fully-qualified name (or two). Not quite as succinct, but I assume the scope of these imports is only local anyway. joinPath root path = jp [root,filename path] where jp = System.FilePath.joinPath filename = System.FilePath.takeFileName or joinPath root path = System.FilePath.joinPath [root,System.FilePath.takeFileName path] Cheers, D ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] some ideas for Haskell', from Python
(defun avg (rest args) (/ (apply #'+ args) (length args))) Or as a macro like this: (defmacro avg (rest args) `(/ (+ ,@args) ,(length args))) The reason the macro is better is that the length of the list is known at compile time, so you don't need to traverse the list to calculate the length of the list. I'm trying to work out how awesome the (+) operator is that you can add the values together without needing to traverse the list ;-) D ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Retrospective on 2008?
On Thu, Dec 11, 2008 at 1:00 PM, Henk-Jan van Tuyl [EMAIL PROTECTED] wrote: Using the commands: cabal update cabal list | fgrep * | wc I counted 927 entries. Unfortunately that's not a reliable means of determining cabal packages. (Baffling, I know.) I think it actually lists things you have installed from other sources, too. For instance: $ cabal list | grep cairo * cairo Homepage: http://haskell.org/gtk2hs/archives/2006/01/26/cairo-eye-candy/ $ cabal install cairo cabal: There is no package named cairo Last time this came up there was mention of adding an option to only list things which cabal has control over. I don't know if anything has come of that idea. Cheers, D -- Dougal Stanton [EMAIL PROTECTED] // http://www.dougalstanton.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] (no subject)
2008/11/25 apostolos flessas [EMAIL PROTECTED]: hi, i am looking for someone to help me with an assignment! can anyone help me? Hi Tolis! Have a look at the homework help policy, so you know what people will and will not answer. http://www.haskell.org/haskellwiki/Homework_help Then let us know what you're trying to do, and what your difficulty has been. Cheers, D ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] strange ghc output
On Mon, Oct 27, 2008 at 4:49 PM, brad clawsie [EMAIL PROTECTED] wrote: -BEGIN PGP SIGNED MESSAGE- Hash: SHA1 i have a small program i have been using routinely that has stopped working. the last alteration of my install configuration was to upgrade the haskell-feed package as arch linux recommended. here is the error i get: - - $ runghc newspage.hs GHCi runtime linker: fatal error: I found a duplicate definition for symbol fps_minimum whilst processing object file /usr/lib/bytestring-0.9.1.3/ghc-6.8.2/HSbytestring-0.9.1.3.o This could be caused by: * Loading two different object files which export the same symbol * Specifying the same object file twice on the GHCi command line * An incorrect `package.conf' entry, causing some object to be loaded twice. GHCi cannot safely continue in this situation. Exiting now. Sorry. - - i have reinstalled the haskell-bytestring package, to no avail. here is the actual code i am trying to run: http://hpaste.org/11514#a0 its fairly straightforward. any clues? Hi Brad, This happens when, for example, your code imports a library which was compiled with a previous version of bytestring. Replacing bytestring on its own isn't enough to solve the problem. To make things more awkward, it could be several libraries which use the old bytestring. Using ghc --make, it seems this error can be ignored, but it's annoying if you want to use the interactive GHC. The only answer I know of is to systematically examine the dependencies of each failing library as it is loaded in GHCi. Then rebuild this library with the new bytestring and try again. This is what I did in the end. Maybe cabal-install provides more sophisticated features for this nowadays; its development seems to be quite pacy! Cheers, D ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Terminal-like Application Design
2008/10/17 Magnus Therning [EMAIL PROTECTED]: I wanted to throw in another idea, something I didn't come up with myself but used in omnicodec[1]. Now I don't remember where I picked up the idea: This method is described in http://www.haskell.org/haskellwiki/High-level_option_handling_with_GetOpt. I have used it in the past and eventually end up with huge Config data structures and not much separation of unrelated parts of the computation. Of course, this is probably just me ;-) Alternatively (and this is where I have had more success) you can take several passes over the command arguments, using different parsers. Each parser just ignores what it doesn't recognise: parseArgs names = do args - getArgs let info = parseWith infoOptions [] let options = parseWith argOptions defaultOptArgs let query = parseWith queryOptions defaultQuery return (info, options, query) where parseWith os z = case getOpt Permute os args of (o,_,_) - foldr id z o Note that this method tends to ignore user error at the command line, but I'm sure a hybrid could be constructed that was more chatty but still quite clean at the back end. See http://www.dougalstanton.net/code/buses/ for this code in its wider context. Cheers, D -- Dougal Stanton [EMAIL PROTECTED] // http://www.dougalstanton.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] howto mix - within do?
On Fri, Oct 17, 2008 at 1:39 PM, Larry Evans [EMAIL PROTECTED] wrote:
do_with_assignment.proto.hs:30:2:
Couldn't match expected type `[]' against inferred type `IO'
Expected type: [t]
Inferred type: IO ()
In the expression: putStr v0=
In a 'do' expression: putStr v0=
Prelude let f = do { v - [999] ; return () }
Prelude :t f
f :: [()]
Prelude :t putStr
putStr :: IO ()
So v - [999] is in the list monad, but putStr is in the IO monad.
The two cannot mix in that way.
This looks like it might be homework so I'll refrain from saying any
more for now. Good luck!
D
___
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] List as input
On Fri, Oct 17, 2008 at 2:21 PM, leledumbo [EMAIL PROTECTED] wrote: So, what's the solution? This one: (l::[Ord]) - readLn doesn't work (because Ord isn't a type constructor). It doesn't even comply to Haskell 98 standard. I want to be able to read any list of ordered elements. I hope to be enlightened, but I'm pretty sure this is not possible. Your readLn has to present a list of some specific type which can be inferred at compile time. Which type is it? String? Int? Something else? Also, neither Show nor Read relate to Ord, so you cannot ever be sure that all Readable/Showable types are Ordered, or that all Ordered types can be Read/Shown. D ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Libraries in home dir
On Thu, Oct 9, 2008 at 2:08 PM, Mauricio [EMAIL PROTECTED] wrote: Hi, I want to use a few libraries from hackage and have already download and built them. Can I install those libraries somewhere in my home dir (I want to avoid installing as root) so that ghc can find them? If so, which options should I give to Setup.hs (with main=defaultMain) so that the libraries are going to be copy to that dir? Dpeending on whether you have (and are using) cabal-install, either $ cabal install diagrams --prefix=$HOME --user or $ runhaskell Setup.lhs configure --prefix=$HOME --user That will (a) put the libraries etc in $HOME/lib and (b) register these packages locally. Hope that helps! D ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] OT: Haskell desktop wallpaper?
2008/10/8 Magnus Therning [EMAIL PROTECTED]: This morning I got tired of my desktop wallpaper (one that ships with Debian's Gnome packages). Typing haskell desktop wallpaper yeilded a lot of links to wallpapers with Colleen Haskell, while she's a beautiful lady it wasn't exactly what I was hoping to find. Hence this email. Where can I find some nice wallpapers inspired by Haskell, or maybe even created by Haskell code? It shouldn't be too difficult to generate some wallpapers. Look at the examples included with the Diagrams package [1]. You could take the Ford circles and have different coloured circles at every startup. You could even have a range of palettes depending on season ;-) [1]: http://code.haskell.org/diagrams/example/examples.html Cheers, D ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Monad transformers [Stacking monads]
On Mon, Oct 6, 2008 at 9:48 PM, Andrew Coppin [EMAIL PROTECTED] wrote: Andrew Coppin wrote: I have some longwinded code that works, but I'm still thinking about how to do this more elegantly. It looks like what I really need is something like type M = StateT State (ResultSetT (ErrorT ErrorType Identity)) Is that the correct ordering? If so, I guess that means I have to somehow construct ResultSetT. Is there an easy way to do that, given that I already have ResultSet? For example, if I put ResultSet into Traversable, would that let me do it? ...and again I'm talking to myself... :-/ So after much experimentation, I have managed to piece together the following facts: - It appears that the outer-most monad transformer represents the inner-most monad. So StateT Foo ListT means a list of stateful computations, while ListT (StateT Foo) means a stateful list of computations. Have you read Monad Transformers Step by Step [1] by Martin Grabmueller? It's a fantastic introduction to these beasties, leading the reader through a series of transformations from pure code to using about 4 different monads/transformers for all sorts of extra features. Seriously recommend it. []: http://uebb.cs.tu-berlin.de/~magr/pub/Transformers.pdf Cheers, D ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Haskell participating in big science like CERN Hadrian...
2008/10/3 Galchin, Vasili [EMAIL PROTECTED]: Hello, One of my interests based on my education is grand challenge science. Ok .. let's take the CERN Hadrian Accelerator. Where do you think Haskell can fit into the CERN Hadrian effort currently? Where do you think think Haskell currently is lacking and will have to be improved in order to participate in CERN Hadrian? Is that the experiment where Picts are accelerated to just short of the speed of light in order to smash through to the Roman Empire? ;-) I don't know what the main computational challenges are to the LHC researchers. The stuff in the press has mostly been about infrastructure --- how to store the gigabytes of data per second that they end up keeping, out of the petabytes that are produced in the first place (or something). Cheers, D ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] flipped IO sequence
2008/10/1 Cetin Sert [EMAIL PROTECTED]: warn :: String → IO Int warn = return 1 putStrLn-- causes an error -- = \msg → return 1 putStrLn msg -- works just fine -- = \msg → putStrLn msg return 1 -- works just fine () :: Monad m ⇒ m b → m a → m b b a = a = \_ → b Why do I get this compile-time error?? How can one define ? [EMAIL PROTECTED]:~/lab/test/qths/p ghc -fglasgow-exts -O2 -o d64x --make demo2.hs system.hs [1 of 2] Compiling Netman.System( system.hs, system.o ) system.hs:23:14: No instance for (Num (IO Int)) arising from the literal `1' at system.hs:23:14 Possible fix: add an instance declaration for (Num (IO Int)) In the first argument of `return', namely `1' In the first argument of `()', namely `return 1' In the expression: return 1 putStrLn This works for me (type signature added so GHCi doesn't choke) Prelude let () = flip () :: IO b - IO a - IO b And thus: Prelude return 1 putStrLn yo yo 1 Prelude You might be having problems with the point-free code: Prelude let warn' = return 1 putStrLn interactive:1:24: Couldn't match expected type `IO a' against inferred type `String - IO ()' In the second argument of `()', namely `putStrLn' In the expression: return 1 putStrLn In the definition of `warn'': warn' = return 1 putStrLn Adding in variable names straightens that out for me: Prelude let warn s = return 1 putStrLn s Prelude warn help help 1 Prelude Cheers, D ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] csv one-liner
2008/9/30 wman [EMAIL PROTECTED]:
I got asked how to do one particular thing in excel, which led to discssion
with our local MSOffice expert.
During the discussion I stated that's it too much of a PITA and that I'd
rather write a script.
Long story short, I promised him a one-liner to show the power and beauty
of Haskell.
I got the csv package from hackage, modified the parseCSVFromFile so it's
returns IO CSV rather than IO (Either ParseError CSV), and finished with
following code
(writeFile output.csv) = (liftM printCSV $ liftM (map updateLine) $
parseCSVFromFile input.csv)
Is there room for improvement ?
Could it still be made into one-liner without modifying the csv module (and
without resorting to
case parseCSVFromFile input.csv of { Left _ - []; Right x - x}
kind of tricks) ?
I have good news for you:
either :: (b -c) (a - c) (Either b a) - c
That type signature is from memory, but you get the idea. You pass in
two functions - one to deal with the Left and the other to deal with
the Right, and it sorts out your result for you.
Cheers,
D
--
Dougal Stanton
[EMAIL PROTECTED] // http://www.dougalstanton.net
___
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Code.haskell.org down
On Mon, Sep 29, 2008 at 4:02 PM, Mitchell, Neil [EMAIL PROTECTED] wrote: Hi, For me, it seems that code.haskell.org is down. Is this the case for other people as well? It seems code.haskell.org regularly looses connectivity for me :-( Thanks Neil http://downforeveryoneorjustme.com/code.haskell.org sez: It's just you. code.haskell.org is up. which I can confirm from independent investigation ;-) (Seriously though, the above site is a great tool for such circumstances.) D ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Hmm, what license to use?
On Fri, Sep 26, 2008 at 11:17 AM, Thomas Davie [EMAIL PROTECTED] wrote: Should you decide not to give someone something based on the fact that you either don't like them, or don't like what they'll do with the thing you give them. That rather depends what you intend to give, doesn't it? :-) Though the analogy is inapt, because the GPL *doesn't* prevent use of software for things you don't like: http://www.gnu.org/licenses/gpl-faq.html#NoMilitary Cheers, D ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Hmm, what license to use?
On Fri, Sep 26, 2008 at 11:32 AM, Thomas Davie [EMAIL PROTECTED] wrote: Sure it does -- it prevents the use of software for things that are closed source. Thing that are closed source is not a use of software. Programs don't become more or less capable of designing rockets or writing subversive literature because the licence changes. The GPL provides an identical number of restrictions in this case as the BSD licence. Either way, the OP subscribes to the GPL ethic. Such arguments cloud the real point of discussion --- which licence (if any) satisfies the permanent freedom clause with some flexibility for linking? D ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: The container problem
On Fri, Sep 26, 2008 at 8:01 PM, Achim Schneider [EMAIL PROTECTED] wrote: But then you'll be happy to know that there's already Data.Stream.List, with more coming at the same speed as we can order pizza for dons. http://hackage.haskell.org/trac/ghc/ticket/915 I was hoping that ticket would reveal the delivery address that we had to send pizza to, but instead it revealed that streams stuff is not scheduled for inclusion until GHC 6.12. :-( Cheers, D ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Notes on the future of Haskell from ICFP
On Fri, Sep 26, 2008 at 11:52 PM, Bryan O'Sullivan [EMAIL PROTECTED] wrote: Here's a writeup I posted from the conference floor this afternoon: http://www.serpentine.com/blog/2008/09/26/some-notes-on-the-future-of-haskell-and-fp/ That's a very ominous title for such a positive write-up! It's all very exciting stuff. Haskell: it may be avoiding success, but it's certainly quite popular. ;-) D ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Packages
2008/9/23 Cetin Sert [EMAIL PROTECTED]: Austin: Let's say I go and compile a library from sources and install it through Cabal. How can I update the binary version of the library Cabal installed after recompiling the library using newer/modified sources? That should happen automatically with cabal-install if the version number in the .cabal file has changed. There doesn't seem to be a good way of forcing cabal-install to recreate a build (eg, if you want to rebuild/reinstall with profiling). I think you need to unregister the package manually first. :-( D -- Dougal Stanton [EMAIL PROTECTED] // http://www.dougalstanton.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] about openTempFile
On Wed, Sep 17, 2008 at 1:17 PM, Manlio Perillo [EMAIL PROTECTED] wrote: The Python tempfile module, as an example, implements a wrapper around mkstemp function that does exactly this, and the code is portable; on Windows it uses O_TEMPORARY_FILE flag, on POSIX systems the file is unlink-ed as soon as it is created (but note that the code is not signal safe - well, many functions in the Python standard library are not signal safe). Something like: withTempFile :: String - ((FilePath, Handle) - IO b) - IO b withTempFile name action = do tmpdir - getTemporaryDirectory bracket (openTempFile tmpdir name) (\(fp,h) - hClose h removeFile fp) action I don't know if this has the safety requirements you mean? -- Dougal Stanton [EMAIL PROTECTED] // http://www.dougalstanton.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Erroneous package listings in hackage?
On Sat, Sep 13, 2008 at 1:51 AM, Duncan Coutts [EMAIL PROTECTED] wrote: Perhaps for packages that are installed but not re-installable via Cabal (like cairo, base, ghc etc) it should say something. Do you have any specific suggestions? Well that explains it then! I had no idea it listed stuff not available from Hackage. I've been using `cabal list | grep foo` to search for packages but that's obviously not optimal, it seems. I don't know what would clarify the matter. An available from Hackage: (yes/no) field? Or a flag to pass to `cabal list` to show Hackage stuff only? D -- Dougal Stanton [EMAIL PROTECTED] // http://www.dougalstanton.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Erroneous package listings in hackage?
$ cabal update ... $ cabal list | less ... * cairo Latest version installed: 0.9.13 Homepage: http://haskell.org/gtk2hs/ License: BSD3 ... $ cabal install cairo cabal: There is no package named cairo I must admit I was surprised to see a gtk2hs module on Hackage, but not half as surprised when I found it wasn't there after all... D ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] packages and QuickCheck
2008/9/9 Conal Elliott [EMAIL PROTECTED]: How do folks like to package up QuickCheck tests for their libraries? In the main library? As a separate repo package? Same repo separate package? Keeping tests with the tested code allows testing of non-exported functionality, but can add quite a lot of clutter. If they're in a separate package it's less easy to wire quickcheck tests into the commit procedure. Cheers, D ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] packages and QuickCheck
On Tue, Sep 9, 2008 at 2:05 PM, Dougal Stanton [EMAIL PROTECTED] wrote: If they're in a separate package it's less easy to wire quickcheck tests into the commit procedure. And by package there, I mean repo. Obviously ;-) D ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Is there GHC 6.8.3 on Ubuntu?
On Thu, Aug 28, 2008 at 7:25 AM, Ketil Malde [EMAIL PROTECTED] wrote: If you want to pack 6.8.3, go for it! If you just wanted to use it, I've had success using the binary snapshots on previous Ubuntus. Agreed. The default Linux binary works fine for me in Hardy Heron, just installed in my ~/bin. D -- Dougal Stanton [EMAIL PROTECTED] // http://www.dougalstanton.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: problem with cabal for syb-with-class
On Tue, Aug 26, 2008 at 2:22 PM, Duncan Coutts [EMAIL PROTECTED] wrote: So when ghc finds that one of your modules needs to import something that is not in one of the given packages it says that it's in another package that is 'hidden'. Of course it's only hidden because Cabal told ghc to hide them. Yes, it is one of those unfortunate error messages that says I know what the problem is *and* how to fix it, but I'm not going to. ;-) Cheers, Dougal ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] HTTP package: connection closing bug?
On Thu, Aug 21, 2008 at 11:44 PM, Aaron Tomb [EMAIL PROTECTED] wrote: I've never looked into it deeply, but I just wanted to chime in that I've seen this, too. I may be confusing it with something else, but I seem to recall something very similar from a while back, in a blog post somewhere? I can't remember the details, but someone was writing a server application of some kind and came across a socket leaking error that was a one-line fix line this. The description and the fix just seem so familiar. :-\ Sorry, this is the most incoherent and useless post! Maybe someone else has been paying more attention and can remember who it was, and where. Cheers, D -- Dougal Stanton [EMAIL PROTECTED] // http://www.dougalstanton.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Is www.haskell.org down?
2008/8/14 Sean Leather [EMAIL PROTECTED]: I can't reach www.haskell.org , and I'm having withdrawal issues. I also can't get any response from it. It's not just you! D ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Alternatives to convoluted record syntax
Hi Haskellers,
This is a style question, as my program works fine but looks really
ugly and can be confusing to maintain.
I take options from the command line using GetOpt and hand back this
structure for later use.
data Opts = Opts
{ query :: Query
, queryLimit:: Maybe Limit
, disabledOnly :: Bool
} deriving Show
Here's a snippet from the parser for one option (others omitted for clarity):
options :: [OptDescr (Opts - Opts)]
options =
[ Option b [bus] (ReqArg busNum NUM) Bus number
, ...
]
where busNum n os = let b = (query os) { queryBusNumber = Just n }
in if isBusId n then os { query = b } else os
Variations on that ugliness are repeated four times for other fields.
Is there an alternative way to change the value of nested fields?
Thanks,
Dougal.
--
Dougal Stanton
[EMAIL PROTECTED] // http://www.dougalstanton.net
___
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Alternatives to convoluted record syntax
On Thu, Jul 3, 2008 at 11:13 AM, Henning Thielemann
[EMAIL PROTECTED] wrote:
infix2 :: ((Char, Int), String)
infix2 =
(('b',7),hallo)$%first^:second^=10
(second^=10) replaces the second member of pair with a value.
(^:) applies that change to the outer record (again a pair).
($%) applies the modifier (first^:second^=10) to a concrete pair.
Hmm! Thanks for the pointer, but I'm not sure that would really clear
things up much. It seems this may just be a wart I'll have to put up
with.
Cheers,
D
--
Dougal Stanton
[EMAIL PROTECTED] // http://www.dougalstanton.net
___
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Call Graph Tool?
On Fri, Jun 27, 2008 at 11:39 AM, Claus Reinke [EMAIL PROTECTED] wrote: If you wanted to go down that route, try using 'ghc --make -v2' and translate that dependency graph to dot. Also, if you want to get a quick 'n dirty list of which of your own files depend on which others, ghc -M $main.hs works quite well. I've had some success in the past shoving this stuff almost directly into the graph libraries and out to graphviz. Be warned that it fiddles with any file called Makefile in your working directory... Cheers, D -- Dougal Stanton [EMAIL PROTECTED] // http://www.dougalstanton.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Polymorphic QuickCheck arguments
2008/6/17 Hugo Pacheco [EMAIL PROTECTED]: Hi all, There is something about polymorphic tests in QuickCheck that I do not understand. If you write the simplest dummy test function tst :: a - Bool tst _ = True and evaluate it we get verboseCheck tst 0: () 1: () ... How come did the polymorphic value a get instanciated to ()? Is this done via the Testable type class? I haven't got something here to check with, but from the formatting it looks like every odd line is a randomly-chosen boolean value, and the following line is the result? It might be just printing the result value of IO (). Maybe try a more complete test to see how that looks? Cheers, D -- Dougal Stanton [EMAIL PROTECTED] // http://www.dougalstanton.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Functional board games
I'm having a go at making a functional board game (the back-end logic for one, at least) and as with all good projects it raises lots of questions. But I'll keep it to one this time. Does anyone know of functional-style implementations of chess/draughts/go/anything else that might give me ideas? I am writing a game of Thud (yes, from the Terry Pratchett book...) but I don't hold much hope of their being a functional-style Thud game already in existence! Cheers, D. -- Dougal Stanton [EMAIL PROTECTED] // http://www.dougalstanton.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Functional board games
On Mon, Apr 21, 2008 at 5:08 PM, Ryan Ingram [EMAIL PROTECTED] wrote: Bertrand Felgenhauer[1] wrote a peg solitaire game[2] using Prompt[3] to interact with the user. Thanks to everyone for the suggestions, particularly the Games page on the Haskell wiki which didn't appear in all my googling atttempts. Also, I had been hoping to have a go with Prompt after I saw it first time round but couldn't remember what it was called! So thanks to Ryan for bringing it up again. Cheers, D. -- Dougal Stanton [EMAIL PROTECTED] // http://www.dougalstanton.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Markup bug in HaskellWiki
On 04/03/2008, Henning Thielemann [EMAIL PROTECTED] wrote: In the Wiki article http://haskell.org/haskellwiki/Comparison_chain there is the piece unzipunzip which is improperly formatted. I guess the wiki uses GeSHi, and it's because of a bug in the keyword list. I reported it to the maintainer a few weeks ago (when I wrote this [1]) but I haven't heard any word back. It's dead easy to fix if someone has access to the PHP source. There's a file called, IIRC, haskell.php with a large list of keywords. Two of them, 'unzip' and 'unzip3' appear twice. Delete one of each and it all works fine again. [1] http://www.dougalstanton.net/blog/index.php/2008/02/12/spot-the-deliberate-mistake -- Dougal Stanton [EMAIL PROTECTED] // http://www.dougalstanton.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Markup bug in HaskellWiki
On 04/03/2008, Wolfgang Jeltsch [EMAIL PROTECTED] wrote: Am Dienstag, 4. März 2008 16:10 schrieb Dougal Stanton: […] There's a file called, IIRC, haskell.php with a large list of keywords. Two of them, 'unzip' and 'unzip3' appear twice. Delete one of each and it all works fine again. Why do they appear at all? They are not keywords. Well, keywords is a bit of a misnomer. Geshi isn't very smart, it just recognises the standard prelude and adds in links to the online API. D -- Dougal Stanton [EMAIL PROTECTED] // http://www.dougalstanton.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] ANN: Leksah 0.1 - Haskell IDE written in Haskell
On 14/02/2008, Alistair Bayley [EMAIL PROTECTED] wrote: I just downloaded this from hackage and went through the usual Cabal ritual. The build fails with Would I be better off getting straight from the darcs repo? I compiled from the darcs repo last night, which worked fine. -- Dougal Stanton [EMAIL PROTECTED] // http://www.dougalstanton.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] FP and Quality
On 07/02/2008, Benjamin L. Russell [EMAIL PROTECTED] wrote: - text follows immediately after this line - Haskell vs. Ada vs. C++ vs. Awk vs. ... An Experiment in Software Prototyping Productivity (1994), by Paul Hudak and Mark P. Jones: http://citeseer.ist.psu.edu/41732.html This one's quite interesting but refers to the much longer report. In the bibliography it is listed as unpublished, but during the text the authors suggest you read it anyway. Does anyone have a source for this document. (A quick search has only produced further citations in other places.) J.A.N. Lee, B. Blum, P. Kanellakis, H. Crisp, and J.A. Caruso. ProtoTech HiPer-D Joint Prototyping Demonstration Project, February 1994. Unpublished; 400 pages. Cheers, D -- Dougal Stanton [EMAIL PROTECTED] // http://www.dougalstanton.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Hamming's Problem
On 18/01/2008, Bertram Felgenhauer [EMAIL PROTECTED] wrote: I have some ideas, but maybe you want to work on a correct solution first? There is an implementation on the wikipedia article for Haskell: hamming = 1 : map (2*) hamming `merge` map (3*) hamming `merge` map (5*) hamming where merge (x:xs) (y:ys) | x y = x : xs `merge` (y:ys) | x y = y : (x:xs) `merge` ys | otherwise = x : xs `merge` ys -- Dougal Stanton [EMAIL PROTECTED] // http://www.dougalstanton.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Filter by several predicates at once
Are the functions passall, passany :: [a - Bool] - a - Bool passall ps v = and $ map ($v) ps passany ps v = or $ map ($v) ps or something similar defined anywhere? Such that one can write filter (passany tests) [0..10] filter (passall tests) [0..10] where tests = [5, odd] Or is there a better way of filtering by several predicates for each value without using filter p3 . filter p2 . filter p1 or filter (\v - p1 v p2 v p3 v) vs Cheers, D -- Dougal Stanton [EMAIL PROTECTED] // http://www.dougalstanton.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Filter by several predicates at once
On 17/01/2008, Stuart Cook [EMAIL PROTECTED] wrote: On Jan 18, 2008 1:46 AM, Isaac Dupree [EMAIL PROTECTED] wrote: nearly; using Prelude: passall ps v = all ($v) ps passany ps v = any ($v) ps Yes, thanks Isaac. That should have been obvious, argh... passall = swing all passany = swing any Whether that's any better than the pointwise version is up to you. I think in this case I will use the explicit version, because I wouldn't remember how swing worked. What is the motivation for the name? ;-) (Do I want to hear the answer...?) D -- Dougal Stanton [EMAIL PROTECTED] // http://www.dougalstanton.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] type questions again....
On 11/01/2008, Nicholls, Mark [EMAIL PROTECTED] wrote: Preferably illustrating it in terms of logic rather than lambda calculus. There's plenty of stuff out there on it….but most of it seems double dutch (no offense to the dutch intended). I think the preferred idiom, considering the notation, is that it's all Greek to me ;-) D -- Dougal Stanton [EMAIL PROTECTED] // http://www.dougalstanton.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Trouble with indentation
On 09/01/2008, Fernando Rodriguez [EMAIL PROTECTED] wrote: However, ghc complains about: parse error on input `=' at the if m = 2 then line. I believe this is some sort of layout error. Can someone point out what I am doing wrong? Assuming the layout didn't get munged during the email process, the problem is that the 'if' can't go there. You need to have 'sth = if ...' not 'if cond then sth = ' diaDeSemana d m a = toEnum num :: DiaSemana where num = zeller x y z zeller x y z = (700 + (26 * x - 2) `div` 10 + d + y + y `div` 4 + z `div` 4 - 2 * z) `mod` 7 if m = 2 then x = m + 10 y = (a - 1) `mod` 100 z = (a-1) 'div' 100 else x = m - 2 y = a `mod` 100 z = a `div` 100 Maybe try: (x,y,z) = if m = 2 then (m+10, (a-1)`mod`100, (a-1)`div`100) else (m-2 , a`mod`100, a`div`100) I haven't tested this though -- Dougal Stanton [EMAIL PROTECTED] // http://www.dougalstanton.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Why purely in haskell?
On 09/01/2008, Yu-Teh Shen [EMAIL PROTECTED] wrote: I got question about why haskell insist to be a purely FL. I mean is there any feature which is only support by pure? Have a look at the ueber-retrospective on Haskell, fifty-five pages of all the history and motivation one could possibly want. http://research.microsoft.com/~simonpj/papers/history-of-haskell/ It's interesting reading, I promise! ;-) D. -- Dougal Stanton [EMAIL PROTECTED] // http://www.dougalstanton.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Hoogle works once more
On 06/12/2007, Neil Mitchell [EMAIL PROTECTED] wrote: Hi, I've just finished updating Hoogle (http://haskell.org/hoogle/) to work with the latest GHC API, in particular all the base split that has occurred and the few functions that were added. It took rather longer than I would have liked, because of paper deadlines etc, but its now sufficiently automated that it should only take a few seconds next time the libraries move in new directions. This is great news. Hoogle is a fantastic tool. Is there a way to search on module names? If I put in Data.Map then the one thing that doesn't come up is a link to the library page for Data.Map. That would be a really good short-cut. Once again, thanks. Cheers, D. -- Dougal Stanton [EMAIL PROTECTED] // http://www.dougalstanton.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Advice for clean code.
On 04/12/2007, Felipe Lessa [EMAIL PROTECTED] wrote: I always thought show was meant for returning a String that could be used to recreate the original data if you copy-pasted it in your code or if you used read (i.e. read . show == id). Reading the documentation more carefully, I see that [1] says that this property holds for *derived* instances, and says nothing about it in the general case. So, what's the deal here? May I use Show for anything without breaking conventions? And how about Read? That seems to be convention though I don't think it's required for the correct operation of anything. Anyone? -- Dougal Stanton [EMAIL PROTECTED] // http://www.dougalstanton.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Haskell code in Wordpress
On 23/11/2007, Paulo J. Matos [EMAIL PROTECTED] wrote: Hi all, I'm curious about the best way to typeset haskell code in a wordpress blog. Using blockquote removes all indentation. :-( There is a code highlighter for wordpress that works for Haskell code, but it's a bit of a pain to use, especially with the visual editor. It'll do a one-way conversion of into gt; whenever you do a preview. :-( It's easy to use though. pre lang=haskell main = putStrLn yo lambda /pre Unfortunately WP isn't really great at handling text-preprocessors like this or Markdown. To work properly they have to subvert the system a bit. D. -- Dougal Stanton [EMAIL PROTECTED] // http://www.dougalstanton.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Searched for mdo on haskell.org. Found nothing.
On 22/11/2007, Richard Kelsall [EMAIL PROTECTED] wrote: Did I do something wrong when searching haskell.org? You didn't use Google first? ;-) Seriously though, using the search box at haskell.org seems to be a dead loss. I'm sure this has come up in the past. D. -- Dougal Stanton [EMAIL PROTECTED] // http://www.dougalstanton.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] ANN: The Monad.Reader Issue 9: SoC special
On 19/11/2007, Wouter Swierstra [EMAIL PROTECTED] wrote: I am pleased to announce that a new issue of The Monad.Reader is now available: http://www.haskell.org/haskellwiki/The_Monad.Reader Thanks Wouter, the haiku look great! ;-) -- Dougal Stanton [EMAIL PROTECTED] // http://www.dougalstanton.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Renaming constructors for readability
I wonder, is there an equivalent of the 'type' keyword for constructors? An example: -- create a pseudo-C pointer type -- which can point to a value or a -- null. type Pointer a = Maybe a -- int a = 3; -- int *pa = a; ampersand :: t - Pointer t ampersand a = Just a -- int b = *pa. star :: Pointer a - a star (Just a) = a -- note this function behaves -- in an 'authentic' fashion ;-) To really complete the illusion it would be nice to replace the names Just and Nothing with PointerTo and Null. Then the constructors would really mean something. Is there a solution? -- Dougal Stanton [EMAIL PROTECTED] // http://www.dougalstanton.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Renaming constructors for readability
On 13/11/2007, Henning Thielemann [EMAIL PROTECTED] wrote: On Tue, 13 Nov 2007, Dougal Stanton wrote: -- int a = 3; -- int *pa = a; ampersand :: t - Pointer t ampersand a = Just a What's bad about using 'ampersand' function as replacement for the constructor 'Just'? I also wanted to use it in pattern matching but have the advantage of all the stuff already written for Maybe. (Note this was an example I made up on the spur of the moment anyway.) I'd often thought it would be nice when adapting standard data structures for specific programs. Like, data Tree a = Leaf a | Branch a [Tree a] data FS a = File a | Folder a [FS a] Once you've got one it would be nice to repurpose it with more appropriate names. Just an idea! :-) D. -- Dougal Stanton [EMAIL PROTECTED] // http://www.dougalstanton.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] words function
On 08/11/2007, Ryan Bloor [EMAIL PROTECTED] wrote: hi I am trying to create a function that uses the words function... I am doing the same thing to each element in a list so I am using mapping techniques. Code... --Define the main first function rStrings2Results :: ([String] - String) - [[String]] - [String] rStrings2Results f(head:tail) = (f head : rStrings2Results f tail) Your description of the problem doesn't relate to the type signature or the solution you have here. I assume the function f which you pass in is meant to be 'words'? In that case, the type signature should be (String - [String]), not the other way round (which would be unwords, or concat, for example). The example solution as it stands also doesn't deal with the empty list. The pattern match against [] will fail. I just want take a list and on the first member (hello my name is ryan) to say [(hello, my, name, is, ryan),..] using the words function. I'm still not completely clear on what you want, so maybe you can clarify. I guess it's something like: [my name is ryan, i am learning haskell, it is fun] - [[my,name, is, ryan],[i am learning haskell, it is fun]] Is this about right? If so, then your type signature should be: f :: (String - [String]) - [String] - [[String]] Although as another poster mentioned, you might think about separating out the head and the tail of the list. It seems to just be a two-element list which could be easily represented as a tuple. f' :: (String - [String]) - [String] - ([String], [String]) Of course I could be very wrong with my interpretation of your problem! Cheers, D. -- Dougal Stanton [EMAIL PROTECTED] // http://www.dougalstanton.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Why can't Haskell be faster?
On 31/10/2007, Peter Hercek [EMAIL PROTECTED] wrote: Anyway, if Haskell would do some kind of whole program analyzes and transformations it probably can mitigate all the problems to a certain degree. I think JHC is supposed to do whole-program optimisations. Rumour has it that its Hello World examples are the fastest around - I have heard it has problems with larger code bases though. ;-) What's the current state of play on this? D. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] viewing HS files in Firefox
On 27/10/2007, Isaac Dupree [EMAIL PROTECTED] wrote: When I try to go to one of the Module.hs files, e.g. on darcs.haskell.org, it now has type HS and Firefox refuses to display it (and only lets me download it). Does anyone know how to make Firefox treat certain file types as others (HS as plain text, in particular)? so that I can browse them with any convenience I've looked into this before but haven't found a satisfactory answer. At best, you can get the offending MIME types to open in a third party text viewer. But I don't know how to force the internal text viewer. Actually, a thought occurs. The address bar prefix view-source: works for html. As in, http://www.haskell.org; - view-source:http://www.haskell.org;. This might be an effective workaround though I don't have a page to test it on right now. Cheers, D. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Suspected stupid Haskell Question
On 17/10/2007, Big_Ham [EMAIL PROTECTED] wrote: Is there a library function to take a list of Strings and return a list of ints showing how many times each String occurs in the list. So for example: [egg, egg, cheese] would return [2,1] I couldn't find anything on a search, or anything in the librarys. Thanks BH. No, but it is also trivial to create, with the 'group' function in Data.List. I'll stop there though, cos this could be a homework question. Cheers, D. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Suspected stupid Haskell Question
On 17/10/2007, Dougal Stanton [EMAIL PROTECTED] wrote: No, but it is also trivial to create, with the 'group' function in Data.List. I'll stop there though, cos this could be a homework question. It's just occurred to me that answering questions like these is a bit like the prisoner's dilemma. - If I give the full answer and no-one else does, then maybe I'm doing someone's homework for them? - If I just give clues and someone else gives the answer, it makes me look mean. :-( - If we all give the answer, everybody's happy and the blame (if it was a set question) is spread around a bit. - If we all answer with vague hints then it makes the list as a whole less useful and seem a bit arrogant. There's no way to win! :-) D. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: New slogan for haskell.org
On 09/10/2007, Alex Tarkovsky [EMAIL PROTECTED] wrote: Brent Yorgey wrote: Aren't you going to make one featuring a catamorphism? =) Done, thanks for the contribution! ;) Goes to look... ...oh, very impressive! ;-) Lolcats seem to have reached a terrifying new nadir. D. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Very crazy
On 25/09/2007, Andrew Coppin [EMAIL PROTECTED] wrote: Type signature is show_system :: [[Double]] - String It takes a matrix representing a system of equations, and pretty prints it. Unfortunately, doing complex formatting like that is... well, complex. The input is quite simple (it's a bunch of numbers), the output is quite simple (it's a neatly formatted string), but the process in the middle is... a mess. I'd like to find a more readable way of doing stuff like this. It's not just this specific function; any general hints would be good. ;-) In this instance I would suggest: (1) Text.Printf (2) Pull out some of those things into separate functions with where/let clauses. If it's a matrix you should probably have something like showMatrix = concatMap showRow Since you'll be applying the same procedures to each line of digits. Cheers, D. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] How can I stop GHCi from calling show for IOactions?
On 20/09/2007, Ryan Ingram [EMAIL PROTECTED] wrote: I think a more consistent behavior would be to not print the LHS at all. If you wanted to print the result of the computation you could just do: Prelude bar 5 or, if you also wanted bound variables afterwards: Prelude (x, Just y) - bar 5 Prelude (x, Just y) Perhaps this is my imperative background speaking, but I don't see much difference at the GHCi prompt between these two: Prelude let x = 5 Prelude x - return 5 I agree with this interpretation. If I want to just *do* the action, I'll type it. If I want to *store* the action then I'll bind it to something. That's the intuition I have, anyway. And it works for pure functions: Prelude let ns = [1..] Prelude [1..] The difference between those two feels like the difference between: Prelude contents - readFile massive.txt Prelude readFile massive.txt But as Ryan mentioned, this may just be poor intuition from an overly imperative mindset... Cheers, D. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] getting crazy with character encoding
On 12/09/2007, Seth Gordon [EMAIL PROTECTED] wrote: I � Unicode. Was it intentional that the central character appears as a little '?', even though the aleph on the line above worked? Either way it would be very amusing, but for different reasons... D ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Can somebody give any advice for beginners?
On 11/09/2007, Peter Verswyvelen [EMAIL PROTECTED] wrote: To me, Haskell was a bit like climbing a mountain which is largely covered by fog; you don't see anything until you've climbed high enough, and then the view is really beautiful ;-) Either that or: the foothills are glorious, but as soon as you get into the higher altitudes you can fall down a monad and not be able to escape... D. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] turning an imperative loop to Haskell
On 06/09/07, Axel Gerstenberger [EMAIL PROTECTED] wrote:
module Main where
import System.IO
import Text.Printf
main :: IO ()
main = do
let all_results1 = take 2 $ step [1]
--print $ length all_results1 -- BTW: if not commented out,
-- all values of all_results
-- are already
-- calculated here
loop [1..50] $ \i - do
let x = all_results1!!i
putStrLn $ show i ++++ show x
-- create an infinite list with values u_{n+1} ++ [u_n,u_{n-1},...,u_1]
-- where u_{n+1} = f (u_n)
step history =
case history of
[] - error no start values
xs - xs ++ (step [ f (head $ reverse (xs) )])
To create an infinite list where each f(u) depends on the previous u,
with a single seed value, use 'iterate':
Prelude let us = iterate f 3
That produces your infinite list of values, starting with [f 3, f(f3),
f(f(f 3)), ...]. Pretty neat.
Then all you really need is
main = mapM_ (uncurry (printf %d %f\n)) (zip [1..50] (iterate f 3))
You can probably shorten this a bit more with arrows but I've got a
cold at the moment and not really thinking straight.
Cheers,
D.
___
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] turning an imperative loop to Haskell
On 06/09/07, Axel Gerstenberger [EMAIL PROTECTED] wrote: however,I don't get it this to work. Is it possible to see the definition of the iterate function? The online help just shows it's usage... The Haskell 98 report includes source for the standard prelude. Check 'em out... http://www.haskell.org/onlinereport/standard-prelude.html Again thanks a lot for your ideas and the links. I knew there was a one-liner for my problem, but I couldn't find it for days. That's a common feeling with Haskell, I think. ;-) D ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] turning an imperative loop to Haskell
On 06/09/07, Sebastian Sylvan [EMAIL PROTECTED] wrote: foo = 2 : 3 : zipWith f (drop 1 foo) foo There's also zipWith3 etc. for functions with more arguments. I think this is called taking a good thing too far, but cool too: f1 u = u + 1 f2 u v = u + v f3 u v w = u + v + w -- functions renamed for consistency) zipWith1 = map zipWith2 = zipWith -- and hey presto! us1 = 3 : zipWith1 f1 us1 us2 = 2 : 3 : zipWith2 f2 (drop 1 us2) us2 us3 = 2 : 3 : 4 : zipWith3 f3 (drop 2 us3) (drop 1 us3) us3 *Main take 10 us1 [3,4,5,6,7,8,9,10,11,12] -- integers from three upwards *Main take 10 us2 [2,3,5,8,13,21,34,55,89,144] -- fibonacci *Main take 10 us3 [2,3,4,9,16,29,54,99,182,335] -- what's this? Cheers, D. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] ANNOUNCE: Guihaskell and PropLang 0.1
On 15/08/07, Asumu Takikawa [EMAIL PROTECTED] wrote: == GuiHaskell Guihaskell is a graphical REPL using PropLang, a GUI combinator library built on top of Gtk2hs, which aims to be an IDE for Haskell written in Haskell. It's still rough around the edges, so think of this as an alpha release. As such, I'd appreciate any feedback very much! Looks interesting. I couldn't see anywhere whether it has any OS dependencies. Is it cross platform? Cheers, D. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Explaining monads
On 14/08/07, Ronald Guida [EMAIL PROTECTED] wrote: My present goal is to understand monads well enough to be able to explain them to others. I wonder if it's possible to create a tutorial that explains monads well enough so that they just make sense or click for people. It seems everyone wants to do this, with not much success! :-( From reading this thread (piecemeal rather than in one concentrated session) I get the impression that no-one agrees on what, if anything, a monad is. If there were a wiki page What_Is_A_Monad and all these ideas were whittled down whenever a counter-proof (such as Identity or Reader) were raised --- what would be left? I get the impression it would look like this: (return x) = f == f x m = return == m (m = f) = g == m = (\x - f x = g) And then where would we be? ;-) I say all this from the point of view of someone who has a reasonably robust intuitive idea of monads that still fails to encompass the List monad. I too would like to understand the overall idea to this monad malarkey... Cheers, D. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
