Re: [Haskell-cafe] CGI module almost useless
[ Moving this thread slowly to the libraries list... ] Bjorn Bringert wrote: John Goerzen wrote: My apologies if this sounds like a bit of a rant; I know people put good effort into this, but The Network.CGI module in fptools (and GHC) is not very useful. I think that it should be removed or re-tooled. Here are the main problems with it: 1. It does not permit custom generation of output headers. Thus the CGI script cannot do things like set cookies, manage HTTP auth, etc. 2. It does not permit generation of anything other than text/html documents. Many CGI scripts are used to manage other types of documents. Notably this makes it incompatible with serving up even basic things like stylesheets and JPEGs. 3. It does not permit the use of any custom design to serve up HTML, forcing *everything* to go through Text.Html. This makes it impossible to do things like serving up HTML files from disk. 4. There is documentation in the code, but it is as comments only, and doesn't show up in the Haddock-generated GHC library reference. (Should be an easy fix) 5. It does not appear to support file uploads in any sane fashion Is there a better CGI module out there somewhere that I'm missing, or should I just set about writing my own? I wrote this module (based on the Network.CGI code) a while ago: http://www.dtek.chalmers.se/~d00bring/darcs/blob/lib/Network/SimpleCGI.hs I don't remember what it does really, but I think it solves issues 1,2,3 and some of 4. Although (among other people) I did some hacking in this module in the remote past, I don't have the time and energy to maintain and/or extend this module anymore. It would be really great if somebody more actively working in this area could take the spec lead here and push the development via discussions here on this library list. John? Björn? A few general design thoughts: * To keep people's mind sane, backwards compatibility with the existing Network.CGI would be a very worthy goal. * Don't use any Haskell language extension available. :-) Currently the module can be used e.g. by Hugs in H98 mode, and keeping it that way would again be something very desirable. Cheers, S. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Combining Haskell and Software Verification
Hello, I have to do a larger project about Software Verification for university. The methods and systems I've seen so far only concern imperative/OOP languages while there seems to be little concerning functional languages. Since the exact topic can be choosen freely and I've already spent too many years messing around with OOP languages, I would like to do a project related to (or using a) functional language, especially Haskell. The problem is, up to now I wasn't successful in finding it. Suggestions are _very_ welcome! regards, Gerd _ Don't just search. Find. Check out the new MSN Search! http://search.msn.com/ ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Using type classes for polymorphism of data constructors
Hi all, I've just started working on a theorem prover (labelled tableaux in case anyone cares) in Haskell. In preparation, I've been attempting to define some data types to represent logical formulae. As one of the requirements of my project is generality (i.e. it must be easily extendible to support additional logics), I've been attempting to build these data types modularly. The end goal in all of this is that the user (perhaps a logician rather than a computer scientist) will describe the calculus they wish to use in a simple DSL. This DSL will then be translated into Haskell and linked against some infrastructure implementing general tableaux bits and pieces. These logic implementations ought to be composable such that we can define modal logic to be propositional calculus with the addition of [] and . In Java (C#, Python, etc) I'd do this by writing an interface Formula and have a bunch of abstract classes (PropositionalFormula, ModalFormula, PredicateFormula, etc) implement this interface, then extend them into the connective classes Conjunction, Disjunction, etc. The constructors for these connective classes would take a number of Formula values (as appropriate for their arity). I've tried to implement this sort of polymorphism in Haskell using a type class, but I have not been able to get it to work and have begun to work on implementing this composition of logics in the DSL compiler, rather than the generated Haskell code. As solutions go, this is far from optimal. Can anyone set me on the right path to getting this type of polymorphism working in Haskell? Ought I be looking at dependant types? Thanks in advance, Thomas Sutton ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
RE: [Haskell-cafe] [Newbie] Quest for inheritance
On 6/6/05, Gracjan Polak [EMAIL PROTECTED] wrote: If you stick to single inheritance there is other way to simulate OO in Haskell. Look for phantom types. Whole wxHaskell (for example) is based on this concept. I heard about them indeed but barely found clear explanations of it. Any useful pointer you're aware of maybe ? Cédric Hi Cedric, See Section 7.3 of the latest revision of Haskell's overlooked object system. There are pointers and explanations. This discussion also clarifies that the phantom approach is tailored for foreign library and component import (but it can be generalized and has been indeed, by Burton in a paper from 1990). Regards, Ralf ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Generalized version of `words'?
Does there exist a generalized version of the `words' function i. e. one that breaks an arbitrary list into parts by an arbitrary predicate? splitAt is not what I need. I had to write my own: -- A version of words, but works with any lists on any predicate. parts pred s = case dropWhile pred s of [] - [] s' - w : parts pred s'' where (w, s'') = break pred s' (just by parameterizing `words' found in Data.List with a predicate passed as a parameter). In case such a function already exists, what is its name? In the opposite case, can such a function be added to the standard library? (or why didn't it exist?) Dimitry Golubovsky Middletown, CT ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
