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Re: [Haskell-cafe] Re: Version 0.4.3 of happs-tutorial is a HAppS job board, done in HAppS.
by Thomas Hartman 29 Sep '08

29 Sep '08

The executable needs the templates in the same directory to work correctly. Copy the happs-tutorial.tar.gz file from whereever cabal put it -- probably somewhere under .cabal if you're on linux. Untar it, cd into the directory, compile and run in there. Should work. I'll revise the tutorial instructions to make this clearer, thanks for the feedback. Thomas. 2008/9/29 Anton Tayanovskyy <anton.tayanovskyy(a)gmail.com>: > Hello Thomas, > > After doing > > sudo cabal install happs-tutorial > > I got HappS to build which is really a great improvement (about a year > ago I could not build HappS). It also installed happs-tutorial > executable. > > Now, the executable runs, but when I try to access the server over HTTP, I get: > > IO Error: Just "templates/base.st" -- does not exist > > Also, on my system I can't locate base.st nor hackInGhci.sh mentioned > in the online tutorial. Actually, I somehow fail to make sense of this > page: > > http://www.happstutorial.com/tutorial/run-tutorial-locally > > After the Cabal install, I'm lost. Maybe it's just me not seeing > something obvious, but in that case it still gives you a good sample > of your target audience, us webmonkeys :) > > If that helps, I'm on Fedora 9, GHC 8.3. > > Thanks. > > > --Anton > > > On Mon, Sep 29, 2008 at 5:25 PM, Thomas Hartman <tphyahoo(a)gmail.com> wrote: >> Someone on reddit pointed out that many firewalls block 5001 so I >> moved to vanilla http port 80. >> >> http://www.happstutorial.com >> >> >> >> 2008/9/29 Thomas Hartman <tphyahoo(a)gmail.com>: >>> Hello, world. >>> >>> In Version 4 of the ongoing self-demoing HAppS Tutorial, we implement >>> a HAppS job board using HAppS. >>> >>> demo: http://happstutorial.com:5001 >>> >>> install: sudo cabal install happs-tutorial >>> >>> darcs head: darcs get http://code.haskell.org/happs-tutorial >>> >>> There aren't any new lessons compared to the last release, but the >>> code is much cleaner, and... well... the web site actually does >>> something. >>> >>> Coming soon, lessons on form processing and HAppS State. >>> >>> Enjoy! >>> >>> Thomas. >>> >> _______________________________________________ >> Haskell-Cafe mailing list >> Haskell-Cafe(a)haskell.org >> http://www.haskell.org/mailman/listinfo/haskell-cafe >> >

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Re: [Haskell-cafe] Re: Haddock + Hoogle == Javadoc on steroids
by Sean Leather 29 Sep '08

29 Sep '08

> > Hi Neil.. my apologies, my nightly cron script clobbered it. Please try > now, same url: http://joyful.com/repos/darcs-sm/api-doc > It seems the "Contents" link embeds the outer frame into the right-hand side inner frame. Otherwise, it looks nice! Sean

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The container problem
by Andrew Coppin 29 Sep '08

29 Sep '08

Take a look around you. Haskell provides several sorts of container. We have: Data.List Data.Set Data.Map Data.Hashtable Data.ByteString Data.Sequence Data.Array Data.Tree Data.IntSet Data.IntMap ... In other words, we have *a lot* of different data containers. And yet, each one provides its own unique API. To anybody used to OO languages, that sounds pretty crazy. In something like Java or Smalltalk or Eiffel, you have an abstract class that represents "container", and maybe a seperate one for "ordered container", and then concrete subclasses for each kind of container. Each one may add a few unique methods of its own, but basically all the containers have a uniform API, and you can write functions that work for any arbitrary [ordered] container. In Haskell, you can't do this. Why is that? To me, it seems that there are two sticking points: 1. Historical reasons. 2. The Haskell '98 type system. (1) is obviously solvable. (2) is harder. Some containers can contain *any* type of data. Haskell permits parametric polymorphism, so this is no problem: Data.List.map :: (a -> b) -> [a] -> [b] Other containers only support *one* type of data: Data.ByteString.Char8.map :: (Char -> Char) -> ByteString -> ByteString The type has a different kind, and the function parameter's type is more constrained. Yet still this poses no problem. However... now try writing a class that both of these functions could be methods of. Good luck with that, by the way... This is AFAIK also the reason why, e.g., Set is *not* an instance of Monad; you can't write a valid instance. The type checker won't have it. To ears accustomed to the OO way, all this makes it sound like Haskell's type system sucks. (Which is rich, because in half the OO languages, you can't write a type-safe container that works for arbitrary element types in the first place! Haskell is a Big Win here.) If I understand this correctly, to solve this problem you need either Functional Dependencies or Associated Types. Is that correct? I also gather that "FDs have problems" - although I have no idea what those problems are. Everybody's hoping that ATs will fix this, but ATs are still kinda new. (Are they even fully implemented in GHC yet?) Can anybody correct/expand on this state of affires? I just want to make sure I understand our position correctly...

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[Haskell-cafe] Version 0.4.3 of happs-tutorial is a HAppS job board, done in HAppS.
by Thomas Hartman 29 Sep '08

29 Sep '08

Hello, world. In Version 4 of the ongoing self-demoing HAppS Tutorial, we implement a HAppS job board using HAppS. demo: http://happstutorial.com:5001 install: sudo cabal install happs-tutorial darcs head: darcs get http://code.haskell.org/happs-tutorial There aren't any new lessons compared to the last release, but the code is much cleaner, and... well... the web site actually does something. Coming soon, lessons on form processing and HAppS State. Enjoy! Thomas.

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not able to compile Happy GLR examples
by brianalexander1＠cableone.net 29 Sep '08

29 Sep '08

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ANNOUNCE: Graphalyze-0.1
by Ivan Miljenovic 29 Sep '08

29 Sep '08

I'd like to announce the initial release of my graph-theoretic analysis library, Graphalyze [1], the darcs repo for which is also available [2]. This is a pre-release of the library that I'm writing for my mathematics honours thesis, "Graph-Theoretic Analysis of the Relationships in Discrete Data". I'll also be releasing a tool that uses this library to analyse the structure of Haskell code, that I'm tentatively calling SourceGraph. As it stands, the library has a number of algorithms included, some of which I've developed from scratch (e.g. clique finder), and others are implementations of published algorithms (mainly the two clustering algorithms). The code is meant to be more readable than efficient, and I wanted to explore ways of developing algorithms that match more closely the way graphs work (which makes FGL a much nicer fit than matrix-based or list-based graph data structures). This library is only a pre-release, as whilst everything in there works (at least it does for me), I'd like to get some feedback from the community, especially since this is my first ever released solo piece of code (I've coded assignments, and worked on projects with others, but have never released anything that I've been solely responsible for before). In particular, have I written the .cabal file correctly? Also, I'd like advice on something else: the part of the library that I'd like to develop still is the reporting framework. The end goal of the library is for the user to specify which algorithms they want applied to their data, and then the library produces a document with the results. This document is _not_ meant to be machine readable. As such, I can think of three options: 1) Plain text, with graphs either in seperate image files (using graphviz) or else as plaintext (FGL's show function). 2) Generate LaTeX code. 3) Generate Pandoc [3] compatible Markdown, and let the user convert it into whatever format they prefer. I'm not a big fan of option 1), as it is probably the most unreadable in general. I'd like to use Pandoc, as it is theoretically possible to convert it to numerous other filetypes, however with inline linking there's still no way (at least I can find) to have images scaled to the correct size automatically. So unless I pre-scale the images, using option 3) and then converting to PDF via LaTex generation of the Markdown sources is probably out. As such, what would you all prefer to read as a documentation-style report of your software? 1) A PDF via LaTeX, which has the advantage of being printable and all in one file 2) HTML via Pandoc, which lets you have the images linked separately from the document, and thus no need to shrink them down (they can stay at the natively generated size, and thus easier to zoom in, etc.). Finally, I'll be giving my honours talk on this next Monday. So if you're in Brisbane on 6 October and interested, it'll be on at 2PM at the University of Queensland (where as part of it I'll be explaining to mathematicians why Haskell is a great language to use for mathematics... or at least trying to!). [1] http://hackage.haskell.org/cgi-bin/hackage-scripts/package/Graphalyze [2] http://code.haskell.org/Graphalyze/ [3] http://johnmacfarlane.net/pandoc -- Ivan Lazar Miljenovic Ivan.Miljenovic(a)gmail.com IvanMiljenovic.wordpress.com

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Code.haskell.org down
by Mitchell, Neil 29 Sep '08

29 Sep '08

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 ============================================================================== Please access the attached hyperlink for an important electronic communications disclaimer: http://www.credit-suisse.com/legal/en/disclaimer_email_ib.html ==============================================================================

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about logical computation
by z_axis 29 Sep '08

29 Sep '08

hi, friends I am a Haskell newbie however i like it very much. After starting learn haskell, i donot find the corresponding "&", "|" , "~", "<<", ">>" logical computation of C language. Sincerely! -------------- z_axis 2008-09-29

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TH error
by Tim Newsham 29 Sep '08

29 Sep '08

I'm goofing with TH and I have my program mostly done: http://hpaste.org/10713 If I have the "$(deriveBinary ''MyData)" line commented out it prints out what looks to me like correct code. I can even paste it into a program and it compiles. However, when the line isn't commented out I get an error I don't understand: test.hs:1:0: Illegal data constructor name: `x' When splicing generated code into the program There are two places in my code I use "x" in splices that could be causing the problem: g <- [| getWord8 >>= \x -> $(caseE [| x |] gcases') |] and put x = $(caseE [| x |] (map return ps)) |] but I don't understand why these might be causing errors (if they are indeed the cause). Using -ddump-splices doesn't help since it seems to hit the error before dumping splices. What's going on here? Tim Newsham http://www.thenewsh.com/~newsham/

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bug in number reading?
by Jason Dusek 29 Sep '08

29 Sep '08

Maybe I'm missing something, but this doesn't seem right... -- _jsn :; ghc -e '10e4' <interactive>:1:0: Warning: Defaulting the following constraint(s) to type `Double' `Fractional a' arising from a use of `it' at <interactive>:1:0-3 In the first argument of `print', namely `it' In the expression: print it In a stmt of a 'do' expression: print it 100000.0 it :: forall t. (Fractional t) => t

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