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hsffig and duplicate typedef declarations
by Dimitry Golubovsky 14 May '09

14 May '09

Dean, I am not sure how HSFFIG would deal with duplicate typedefs (I'm afraid you get error from gcc when processing hsc2hs output). In case you haven't seen this, I put a repo for HSFFIG here recently: http://code.haskell.org/hsffig/ Before running "cabal install" run make at the toplevel of the repo first. I have fixed some glitches recently, and adjusted both hsffig and ffipkg to work with contemporary GHC and Cabal (at least 1.6.0.x). I'd be glad to get any feedback on HSFFIG. E-mail me to "golubovsky at gmail dot com". Thanks. -- Dimitry Golubovsky Anywhere on the Web

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RE: [Haskell-cafe] Developing 3 dimensional interactive environments/functional objects
by paulfrancis＠friendbliss.com 14 May '09

14 May '09

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PhD position in Nottingham
by vxc＠Cs.Nott.AC.UK 14 May '09

14 May '09

PhD position in Type Theory at Nottingham ----------------------------------------- A new PhD position is available in the Functional Programming Laboratory at the University of Nottingham. The topic of research for the project is "Programming and Reasoning with Infinite Structures": it consists in the theoretical study and development of software tools for coinductive types and structured corecursion. The candidate must be a UK resident with an excellent degree in Computer Science or Mathematics at MSc (preferred) or BSc level (first class or equivalent). The applicant should have a good background in mathematical logic, theoretical computer science or functional programming. (S)he should be interested doing research in type theory, constructive mathematics, category theory and foundations of formal reasoning. We offer: PhD place with living expenses (standard UK level) for 3 years. The grants also provide laptops and travel expenses for conference and workshop visits. Nottingham University provides a vibrant research environment in the Functional Programming Laboratory. Deadline for applications: 20 June 2009. Send a cover letter and your CV to Venanzio Capretta (vxc(a)cs.nott.ac.uk) Please contact me for any additional information that you need. This message has been checked for viruses but the contents of an attachment may still contain software viruses, which could damage your computer system: you are advised to perform your own checks. Email communications with the University of Nottingham may be monitored as permitted by UK legislation.

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Fun with type functions
by Simon Peyton-Jones 14 May '09

14 May '09

Friends Ken, Oleg, and I have been working on a tutorial paper about type families (aka associated data types, or type functions). It's in draft at the moment, and we'd really appreciate feedback that would help us improve it. Here it is: http://haskell.org/haskellwiki/Simonpj/Talk:FunWithTypeFuns Thank you! Simon

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Functional Reactive Web Application Framework?
by Petr Pudlak 14 May '09

14 May '09

Hi, I've been learning Haskell for a few months, and it has influenced my thinking about programs quite a lot. Most of my current work is creating complex web applications. Naturally, I was thinking about how to make rich internet applications (and GUI apps in general) in an (utmost :-)) functional way. Recently I found out the concepts of functional reactive programming <http://www.haskell.org/haskellwiki/Functional_Reactive_Programming>, which supersede and generalize my ideas. My question is: "Is there a FRP web application framework, or perhaps an effort to create one?" If not, I'd be willing to start such a project, but since I'm not very experienced Haskell programmer, I'd most likely need some help from somebody more experienced. If somebody would be interested, my ideas go as follows: Handling events in GUI/RIA applications can be very tedious, especially for complex applications. Instead, I'd prefer something like that: 1) Abstract what a user wants to see using a structured datatype, specifically tailored for the application. You may imagine it as something like a structured URL. This can be then viewed as a FRP behavior -- a function of the user's request depending on time. 2) The data that will be displayed on the page are a function of this structured user request and an environment, which is usually database. This is again a behavior. 3) Finally, the resulting page is a function of the data (again a behavior). 4) User actions that change the application state (update the database) could be viewed as FRP events. So instead of handling tons of events, the programmer would construct the application mostly by composing behaviors. Only state-changing user actions would be handled as events. Does anybody see these ideas as useful? Constructive criticism is welcomed. Best regards, Petr

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[ANNOUNCE] Bindings for libguestfs
by Richard W.M. Jones 14 May '09

14 May '09

I added some partial bindings for libguestfs[1] here: http://git.et.redhat.com/?p=libguestfs.git;a=blob;f=haskell/Guestfs.hs;hb=H… Some very simple example programs which use these bindings: http://git.et.redhat.com/?p=libguestfs.git;a=tree;f=haskell;hb=HEAD Any comments welcome. My Haskell skills are pretty terrible, so I'm sure there are many ways these can be improved. If someone wants to look at binding the rest of the API, then please send me some patches. (Note that the Guestfs.hs file is automatically generated). BTW, I found the documentation on writing FFIs very contradictory and incomplete. For example, I was completely defeated trying to find ways to do simple stuff like passing in integers or returning booleans. *Potentially* Haskell's FFI seems like it might be one of the best out of the languages I've used so far, but it needs way more documentation and examples. Rich. [1] http://et.redhat.com/~rjones/libguestfs/ -- Richard Jones, Emerging Technologies, Red Hat http://et.redhat.com/~rjones virt-df lists disk usage of guests without needing to install any software inside the virtual machine. Supports Linux and Windows. http://et.redhat.com/~rjones/virt-df/

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Darcs as undo/redo system?
by Peter Verswyvelen 14 May '09

14 May '09

If you work with a text editor like Microsoft Visual Studio (maybe also Eclipse, don't know), each text editor has its own undo/redo history. However, when you perform refactoring - like renaming a function - this becomes an undo/redo on multiple files together, so in a sense these changes are part of a global history. You can combine these two different kinds of mutations, and undo/redo still works as expected. I don't know how hard this is to implement, but it looks like this problem is somehow is related to Darcs theory of patches (which I don't know yet :-)

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IO trouble
by Xiao-Yong Jin 14 May '09

14 May '09

Hi, I can't really describe it in the subject. So let me try to do it here. I have two functions > f :: a -> b > g :: (a -> b) -> c -> d and I use them as > gf :: c -> d > gf = g f Now I want to handle exceptions in f and redefine f as in f' > f' :: a -> IO (Either e b) So my question is how to define gf' now to use f' instead of f? > gf' :: c -> IO (Either e d) Thanks in advance. Xiao-Yong -- c/* __o/* <\ * (__ */\ <

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hsffig and duplicate typedef declarations
by Dean Herington 14 May '09

14 May '09

I have a large body of C/C++ code at work that I'd like to be able to access from Haskell via FFI. Because the interface to this code is broad, hsffig would seem to be ideal for the task. I've run across one serious hitch, though. The existing #include file graph is complicated and ends up declaring some typedefs multiple times (albeit in consistent ways). While gcc (for example) rejects such practice, the Windows C compiler we're using accepts it. Does anyone know how feasible it would be to get hsffig to accept such practice as well? I've started looking at the hsffig code (and discovered that the C grammar hsffig uses seems to get confused by duplicate typedefs), but thought I'd ask the list in parallel with my further study. Thanks. Dean

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question on the Prelude .. vis-a-vis
by Vasili I. Galchin 14 May '09

14 May '09

Hello, I am seriously punching my way to build Swish via .cabal ... My head is totally to the wall .... punch .. punch ..... Graham Lyle has written some seriously beautiful code .... I am trying to get to adhere to contemporary Haskell namespace convention ..... I still awaiting response from Graham vis-a-vis posting on Hackage ... I strongly think that in bioinformatics and also oil/gas industry(<< I am stuck here everyday ;^)) that Swish is a strong arena of discussion! In any case .. there are some issues: 1) I strongly suspect that in Swish 0.2.1 that some of Graham's libaries are already superseded by the Haskell prelude , e.g. HUnit, Parsec(!!!), his Sort directory/library .. Don ...please 2) Graham wrote a deterministic finite automaton ..... which is giving some grieve namespace-wise ..... please see following Swish/HaskellRDF/Dfa/Dfa.lhs:1:0: Failed to load interface for `Prelude': it is a member of package base, which is hidden vigalchin here is a fragement of Dfa.lhs: > {-# OPTIONS -fglasgow-exts #-} > {-# OPTIONS -fallow-undecidable-instances #-} > module Swish.HaskellRDF.Dfa.Dfa ( > Re(..), > matchRe, > matchRe2 > ) where > {- ???? > import Control.Monad.Identity > import Control.Monad.Reader > import Control.Monad.State > import Data.FiniteMap > import List > import Data.Array > -} import IOExts The type of a regular expression. > data Re t "Dfa.lhs" 609 lines, 18871 characters Very kind regards, Vasili

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