- Haskell-Cafe - Haskell.org

STM and FFI
by Mauricio 11 Sep '08

11 Sep '08

Hi, Is it possible to use foreign function interface with STMs? If so, where can I find examples? Thanks, Maurício

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Re: [Haskell-cafe] packages and QuickCheck
by Sean Leather 10 Sep '08

10 Sep '08

> 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. > I have QuickCheck properties plus HUnit tests, but I think the question is the same. For me, it's in the same repository and shipped with the package source. I think that if you ship source (even via Hackage), you should also ship tests. So, if somebody wants to modify the source, they can run the tests. And making it convenient to test is very important, so I have "cabal test" (or "runhaskell Setup.hs test" without cabal-install) configured to run the tests. I don't think tests should (in general) be part of the user-visible API, so I have them external to the module hierarchy. Testing non-exported functionality without exporting the test interface seems difficult in general. Is there a way to hide part of a module interface with Cabal? Then, you could have a 'test' function exported from each module for testing but hidden for release. My current leaning is to split a package "foo" into packages "foo" and > "foo-test" > What benefit does this provide? Thanks, Sean

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Haskell stacktrace
by Pieter Laeremans 10 Sep '08

10 Sep '08

Hello, I've written a cgi script in haskell, it crashes sometimes with the error message Prelude . tail : empty list In Java we would use this approach to log the erro try { } catch (Exception e) { } -- Pieter Laeremans <pieter(a)laeremans.org> "The future is here. It's just not evenly distributed yet." W. Gibson

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User defined annotations for Haskell (Was: [Haskell-cafe] packages and QuickCheck)
by Max Bolingbroke 10 Sep '08

10 Sep '08

2008/9/10 Johannes Waldmann <waldmann(a)imn.htwk-leipzig.de>: > >>> Has there ever been a discussion of typed, user-definable, >>> user-processable source code annotations for Haskell? >> >> afair it was on haskell-prime list > > http://hackage.haskell.org/trac/haskell-prime/ticket/88 > > if you can call that a discussion :-) I had to implement a kind of annotation system for GHC as part of my Summer of Code project for compiler plugins. You can see a discussion at http://hackage.haskell.org/trac/ghc/wiki/Plugins/Annotations, though I was not aware of that Haskell' ticket. The system as I have implemented is quite basic: the absolute minimum I needed for plugins. The syntax is essentially: {-# ANN foo "I am an annotation!" #-} Where "I am an annotation" may be replaced with any Typeable value, and is subject to staging requirements analgous to Template Haskell (e.g. you may not refer to things in the module being compiled other than by Template Haskell Name). As well as values you can annotate types and modules, and annotations are accessible via the GHC API. See that wiki page for full details. This system has not yet been merged into GHC (or even code reviewed by GHC HQ), so if/when it becomes available to end users the design may have changed drastically. Cheres, Max

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trying to understand monad transformers....
by Daryoush Mehrtash 10 Sep '08

10 Sep '08

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Functional references
by Tim Newsham 10 Sep '08

10 Sep '08

I'm playing with functional references and looking for some feedback on a small FRec library I put together: http://www.thenewsh.com/~newsham/FRef.hs Novel (I think) is that the library is applied to some data accesses that are not normally covered by functional references -- ie. extracting words or replacing words in a string or values in an association list. I'm hoping it will provides a useful framework for editing complex values such as data embedded in Base64 cookies in an HTTP header. Tim Newsham http://www.thenewsh.com/~newsham/

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Unicode and Haskell
by Mattias Bengtsson 09 Sep '08

09 Sep '08

Today i wrote some sample code after a Logic lecture at my university. The idea is to represent the AST of propositional logic as an ADT with some convenience functions (like read-/show instances) and then later perhaps try to make some automatic transformations on the AST. After construction of the Show instances i found the output a bit boring and thought that some Unicode math symbols would spice things up. What happens can be seen in the attached picture (only 3k, that's ok right?). My terminal supports UTF-8 (when i do cat Logic.hs i can see the unicode symbols properly). What might be the problem? regards Mattias

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haskell core definition
by Vlad Skvortsov 09 Sep '08

09 Sep '08

Hi, I'm trying to profile my haskell code (see thread "profiling in haskell") and to get more insight I made GHC produce the haskell Core code. However, I'm not quite sure how to interpret it, is there a definition (quick search didn't reveal one)? Also, how do I demangle the names? It seems that, for example, 'base:GHC.Base.ZC' is a (:) function on strings, but where how am I supposed to figure that out? Thanks! -- Vlad Skvortsov, vss(a)73rus.com, http://vss.73rus.com

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Hackage -> MacPorts?
by John MacFarlane 09 Sep '08

09 Sep '08

It would be great if there were an automated or semi-automated way of generating a MacPorts Portfile from a HackageDB package, along the lines of dons' cabal2arch. Has anyone been working on such a thing? And, are any haskell-cafe readers MacPorts committers? John

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packages and QuickCheck
by Conal Elliott 09 Sep '08

09 Sep '08

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. My current leaning is to split a package "foo" into packages "foo" and "foo-test", but first I'd like to hear about others' experiences, insights, and preferences. Thanks, - Conal

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