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Where prelude alternatives/ classes and types to get values?
by Marc Weber 17 Feb '07

17 Feb '07

The prelude has some issues such like Map.empty, Sequnce.empty, Set.empty It would be much nicer to use class Empty where empty :: a except of more complicated error messages (especially for newbies) Are there already some proposals? Is this the right place to discuss these topics? I got this idea because I'm currently learning more about webfunctions. Some states (eg counters) are implemented using IORefs. I could imagine a class class ModifyIO m c where modify :: IORef a -> ( a -> a ) -> m c data Old a data New a data OldNew a = OldNew a a; modify f = do a <- readIORef io let new = f a writeIORef io new return $ f old new instance ModifyIO IO (Old a) = modify io f = modify io (\old _ -> Old old) instance ModifyIO IO (New a) = modify io f = modify io (\_ new -> New new) instance ModifyIO IO (OldNew a) = modify io f = modify io OldNew which would lead to code such as ... = do (New count) <- modify ioCounterRef (+1) ... compared to ... = do count <- readIORef ioCounterRef let count = count + 1 writeIORef ioCounterRef count ... Do you think this style is insane? Marc Weber

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Submitting a darcs patch
by Rob Hoelz 15 Feb '07

15 Feb '07

I just made some small changes (I figure smaller would be better for my first patch, and I'm also new to Haskell) to the Xlib bindings, adding support for property events and implementing an XGetAtomName function. Seeing as I'm new to darcs, how do I submit a patch and to whom do I submit it? I've already made the patch with darcs record. Thanks, Rob Hoelz

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Compiling Haskell X11 bindings
by Rob Hoelz 14 Feb '07

14 Feb '07

Hello everyone, I've been trying to improve the Haskell X11 bindings so they're more usable. So I tried to compile with my changes, and here's the output: rob@TheRing ~/programming/src/darcs/X11 $ runhaskell Setup.hs configure <A bunch of output that's ok> configure: creating ./config.status config.status: creating config.mk config.status: creating X11.buildinfo config.status: error: cannot find input file: include/HsX11Config.h.in How can I remedy this? I'm looking forward to seeing my changes in action! Thanks, Rob Hoelz

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swap minView/maxView return value.
by Jean-Philippe Bernardy 13 Feb '07

13 Feb '07

Some time ago (before ghc 6.6 / base 2.0 release), I introduced minView and maxView in Data.Set and Data.Map (at a user's request). I agreed with Robert Dockins to implement the same functionality as in his version of the Edison library. Unfortunately, I uselessly swapped the return values of minView and maxView, introducing a difference both with the corresponding functions in the edison library and similar functions in Data.Map/Set. I propose to restore the symmetry, at the cost of incompatibility. The incompatibility is probably acceptable because the functions are still short-lived. See the trac ticket for details. http://hackage.haskell.org/trac/ghc/ticket/1134 I provide no patch nor QuickCheck properties because of the triviality of the change. Cheers, JP.

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Proposal: add extra readline completion functionality
by Judah Jacobson 12 Feb '07

12 Feb '07

I propose adding some functionality to the readline package (really just wrappers of variables from that library) which is necessary to fix ghci bug #998. See the proposed patch at http://hackage.haskell.org/trac/ghc/ticket/1141 as well as the bug report at http://hackage.haskell.org/trac/ghc/ticket/998 The main addition is rl_completion_word_break_hook, which lets us change the set of word break characters based on the context of the line. Specifically for ghci, this is needed to change whether "/" is a word boundary (depending on whether we're expanding a Haskell name or a filename). Note that this variable is only present in readline version 5.0 or later; I've put in some ifdef's to support compiling against older versions. I've also included get/set functions for the rl_attempted_completion_over variable. If it's set to nonzero, readline won't use its default completer when our custom completer returns no results. Thanks, -Judah

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Proposal: Data.Proxy
by Musasabi 09 Feb '07

09 Feb '07

Hello I propose a module called Data.Proxy into the base package containing the common Proxy type used in many different libraries (e.g. HAppS, HList, ...). Attached is the source code. - Einar Karttunen

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Re: Proposal: Make StateT in mtl lazy
by Yitzchak Gale 08 Feb '07

08 Feb '07

Ian Lynagh wrote: > > Control.Monad.State.Class -- for the MonadState class > > Control.Monad.State.Lazy > > Control.Monad.State.Strict > > Control.Monad.State -- re-exports .Class and .Lazy > > Now done. Wonderful news! Thanks! -Yitz

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[Fwd: Re: [GHC] #1134: swap minView/maxView return value]
by Christian Maeder 07 Feb '07

07 Feb '07

It should be allowed to fix a buggy interface (before the bug becomes a feature) Christian -------- Original-Nachricht -------- Betreff: Re: [GHC] #1134: swap minView/maxView return value Datum: Tue, 06 Feb 2007 23:59:25 -0000 Von: GHC <trac(a)galois.com> Antwort an: glasgow-haskell-bugs(a)haskell.org An: glasgow-haskell-bugs(a)haskell.org Newsgruppen: gmane.comp.lang.haskell.glasgow.bugs Referenzen: <071.1d16a01fab839e0adc11599f4864434e@localhost> #1134: swap minView/maxView return value ----------------------------+----------------------------------------------- Reporter: jpbernardy | Owner: jpbernardy Type: proposal | Status: new Priority: normal | Milestone: 6.8 Component: libraries/base | Version: 6.6 Severity: normal | Resolution: Keywords: collections | Difficulty: Easy (1 hr) Testcase: | Architecture: Unknown Os: Unknown | ----------------------------+----------------------------------------------- Changes (by igloo): * milestone: 6.6.1 => 6.8 * type: bug => proposal Comment: Unfortunately fixing this for 6.6.1 would mean changing the interface, which we don't allow within a stable branch. -- Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/1134> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Compiling module using Data.Time with -O fails; can't find HsTime.h
by Alistair Bayley 06 Feb '07

06 Feb '07

If I try to compile this Main.hs: module Main where import Data.Time main = getCurrentTime >>= print with this ghc-6.6 command: ghc --make Main -o test -O ... I get this error: C:\DOCUME~1\bayleya\LOCALS~1\Temp\ghc728_0\ghc728_0.hc:8:20: HsTime.h: No such file or directory Is this me doing something I shouldn't, or is there something wrong with the way the library has been distributed? Alistair

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Adding binarySize to Binary
by Musasabi 05 Feb '07

05 Feb '07

Hello I keep wanting something like: binarySize :: Binary a => Proxy a -> (Int,Maybe Int) in the Data.Binary for returning the minimum and maximum (or Nothing for infinite) space requirements for objects of a given type. Proxy is just defined as "data Proxy t = Proxy", but omitting it is also possible. Would other people consider this an useful addition? - Einar Karttunen

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