Re: [Haskell-cafe] Yet Another Forkable Class
Hi. On 23 August 2013 13:29, Nicolas Trangez nico...@incubaid.com wrote: Did anyone ever consider using type-level literals (strings) to 'name' effects (or transformer layers when using monad stacks)? Edwin Brady had this in his effects library in Idris. http://www.idris-lang.org/documentation/effects/ Ozgur. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] llvm on macos
Hi. On 15 August 2013 20:35, Carter Schonwald carter.schonw...@gmail.comwrote: Just brew install llvm should work fine. I wonder what makes you think this is the case. At this moment in time, `brew install llvm` will install llvm-3.3. Using llvm-3.3, I get warnings and errors. Using llvm-3.2, I get warnings but I never got any errors. This is not to say that they cannot happen on other packages. I've just uninstalled 3.2, installed 3.3, and tried to compile a project of mine. One of its dependencies, data-default-class, failed to compile. The following is what happened on my computer. Hope this helps, Ozgur. $ ghc --version The Glorious Glasgow Haskell Compilation System, version 7.6.3 $ cabal --version cabal-install version 1.16.0.2 using version 1.16.0 of the Cabal library $ cabal install --force-reinstalls --disable-documentation --disable-library-profiling --disable-executable-profiling --ghc-options=-fllvm data-default-class Resolving dependencies... Configuring data-default-class-0.0.1... Building data-default-class-0.0.1... Preprocessing library data-default-class-0.0.1... [1 of 1] Compiling Data.Default.Class ( Data/Default/Class.hs, dist/build/Data/Default/Class.o ) You are using a new version of LLVM that hasn't been tested yet! We will try though... wrong initalizer for intrinsic global variable [0 x i8*] undef Broken module found, compilation aborted! 0 libLLVM-3.3.dylib 0x00010223faee llvm::sys::PrintStackTrace(__sFILE*) + 40 1 libLLVM-3.3.dylib 0x00010223fef5 SignalHandler(int) + 241 2 libsystem_c.dylib 0x7fff8601f94a _sigtramp + 26 3 libsystem_c.dylib 0x000102a10a00 _sigtramp + 2090799312 4 libLLVM-3.3.dylib 0x00010223fd6d abort + 22 5 libLLVM-3.3.dylib 0x000101f08466 (anonymous namespace)::Verifier::abortIfBroken() + 236 6 libLLVM-3.3.dylib 0x000101f07b97 (anonymous namespace)::Verifier::doFinalization(llvm::Module) + 3477 7 libLLVM-3.3.dylib 0x000101ef63a4 llvm::FPPassManager::doFinalization(llvm::Module) + 56 8 libLLVM-3.3.dylib 0x000101ef5e52 llvm::FunctionPassManagerImpl::doFinalization(llvm::Module) + 62 9 libLLVM-3.3.dylib 0x000101ef5d43 llvm::FunctionPassManager::doFinalization() + 21 10 opt 0x000101be19aa std::vectorstd::pairllvm::BasicBlock*, llvm::SuccIteratorllvm::TerminatorInst*, llvm::BasicBlock , std::allocatorstd::pairllvm::BasicBlock*, llvm::SuccIteratorllvm::TerminatorInst*, llvm::BasicBlock ::_M_insert_aux(__gnu_cxx::__normal_iteratorstd::pairllvm::BasicBlock*, llvm::SuccIteratorllvm::TerminatorInst*, llvm::BasicBlock *, std::vectorstd::pairllvm::BasicBlock*, llvm::SuccIteratorllvm::TerminatorInst*, llvm::BasicBlock , std::allocatorstd::pairllvm::BasicBlock*, llvm::SuccIteratorllvm::TerminatorInst*, llvm::BasicBlock, std::pairllvm::BasicBlock*, llvm::SuccIteratorllvm::TerminatorInst*, llvm::BasicBlock const) + 6988 11 libdyld.dylib 0x7fff8959c7e1 start + 0 12 libdyld.dylib 0x0006 start + 1990604837 Stack dump: 0. Program arguments: opt /var/folders/h5/3mmbxydn5qs3w9f3j6mgmhscgn/T/ghc11789_0/ghc11789_0.ll -o /var/folders/h5/3mmbxydn5qs3w9f3j6mgmhscgn/T/ghc11789_0/ghc11789_0.bc -O1 --enable-tbaa=true llc: /var/folders/h5/3mmbxydn5qs3w9f3j6mgmhscgn/T/ghc11789_0/ghc11789_0.bc: error: Could not open input file: No such file or directory Failed to install data-default-class-0.0.1 cabal: Error: some packages failed to install: data-default-class-0.0.1 failed during the building phase. The exception was: ExitFailure 1 ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] llvm on macos
On 11 August 2013 17:48, Dominic Steinitz domi...@steinitz.org wrote: I seem to be running LLVM 3.2 so I am a bit puzzled by the warning. Is it because I am running ghc 7.6.2? I get the warning too, but nothing seems to be broken with 3.2. This is what I meant to say, sorry if I was confusing. -- Ozgur Akgun ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] llvm on macos
Hi. On 10 August 2013 18:20, Brandon Allbery allber...@gmail.com wrote: There may be some support for requesting specific versions from Homebrew. Try `brew versions llvm`. Then, you'll need to run the git checkout command in `brew --prefix` directory. I am using llvm 3.2 because I had a few ghc related problems with llvm 3.3. Never had any problems with 3.2 though. Hope this helps, Ozgur ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Casting newtype to base type?
Hi Vlatko. On 2 July 2013 16:03, Vlatko Basic vlatko.ba...@gmail.com wrote: Is there a nicer way to extract the 'IO String' from 'IOS', without 'case' or without pattern matching the whole 'P'? You might enjoy the newtype package. http://hackage.haskell.org/package/newtype Hope this helps, Ozgur. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] TH clause Pat selection
Hi. On 19 June 2013 23:23, Brian Lewis br...@lorf.org wrote: The problem is, I don't know how to generate the function's clauses. foo 0 = ... seems to be a LitP pattern. But foo True = ... seems to be a ConP pattern. The appropriate pattern depends on type c. I've used haskell-src-meta for this purpose before. See: http://hackage.haskell.org/packages/archive/haskell-src-meta/0.6.0.2/doc/html/Language-Haskell-Meta-Parse.html#v:parsePat Hope this helps, Ozgur ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Backward compatibility
Hi, On 3 May 2013 11:43, Tobias Dammers tdamm...@gmail.com wrote: PS The proposal to fix Functor = Applicative = Monad has patches attached for GHC and base, but the backwards compatibility bogeyman always seems to trump something that will break a lot of code. This kind of breaks everything changes would require something similar to what Python is doing with the 2 - 3 transition, and considering how painfully slowly it is progressing there, I understand perfectly well why people don't want to go there. There is one very big advantage in the Haskell-world though. Most of the struggle will be at the compile time. The biggest headache caused by the Python 2 - 3 transition is how you get a runtime error 2 weeks after you think you've fixed everything! (Yeah, I know code coverage analysis is an option when you don't have static type checking, but ...) Cheers, Ozgur ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Haskell compilation errors break the complexity encapsulation on DSLs
Hi, On 27 April 2013 10:07, Alberto G. Corona agocor...@gmail.com wrote: I created a ticket for the feature request: Ticket #7870 Teachers, newbies and people working in Industry: Please push it! A link to the ticket may be helpful for the lazy. http://hackage.haskell.org/trac/ghc/ticket/7870 I quite like this idea, and I think this is one thing people use TH for now instead. (Using quasi-quotes, you can produce any compilation error you like...) It would be great if we didn't have to pull in the full power of TH (or QQ) for this. Cheers, Ozgur ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] cabal install choosing an older version
Hi, I noticed a weird behaviour with cabal-install. When I run `cabal install hspec --dry-run -v` cabal-install correctly picks hspec-1.4.3 (the latest version). However, when I run `cabal install ansi-terminal hspec --dry-run -v`cabal-install tries to install hspec-0.3.0 for no apparent reason. This is with a clean user package db. Following is some info about my system. $ ghc --version The Glorious Glasgow Haskell Compilation System, version 7.6.1 $ cabal --version cabal-install version 1.16.0.2 using version 1.16.0.3 of the Cabal library $ ghc-pkg list --user $ cabal install hspec --dry-run -v Reading available packages... Choosing modular solver. Resolving dependencies... In order, the following would be installed: HUnit-1.2.5.1 (new package) ansi-terminal-0.5.5.1 (new package) hspec-expectations-0.3.0.3 (new package) random-1.0.1.1 (new package) QuickCheck-2.5.1.1 (new package) setenv-0.1.0 (new package) silently-1.2.4.1 (new package) transformers-0.3.0.0 (new package) hspec-1.4.3 (new package) $ cabal install ansi-terminal hspec --dry-run -v Reading available packages... Choosing modular solver. Resolving dependencies... In order, the following would be installed: HUnit-1.2.5.1 (new package) ansi-terminal-0.6 (new package) extensible-exceptions-0.1.1.4 (new package) random-1.0.1.1 (new package) QuickCheck-2.5 (new package) hspec-0.3.0 (new package) -- Ozgur Akgun ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] cabal install choosing an older version
Aha! I think I know why this happens. The latest versions of ansi-terminal and hspec do not work together. Cabal picks the latest ansi-terminal (0.6) first, then the latest hspec that doesn't conflict with this choice is 0.3.0. I can confirm this by the following: $ cabal install hspec ansi-terminal --dry-run -v Reading available packages... Choosing modular solver. Resolving dependencies... In order, the following would be installed: HUnit-1.2.5.1 (new package) ansi-terminal-0.5.5.1 (new package) hspec-expectations-0.3.0.3 (new package) random-1.0.1.1 (new package) QuickCheck-2.5.1.1 (new package) setenv-0.1.0 (new package) silently-1.2.4.1 (new package) transformers-0.3.0.0 (new package) hspec-1.4.3 (new package) When hspec comes before ansi-terminal, the latest version for hspec is selected and an older version of ansi-terminal is used. Maybe cabal-install should backtrack more and pick a *more optimal *set of latest versions, I don't know. If this is desired, a proximity of the selected versions to the latest available versions might be a good measure. Best, Ozgur ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] cabal install choosing an older version
Hi Max, On 25 January 2013 15:58, Max Bolingbroke batterseapo...@hotmail.comwrote: If this happens because the dependency bounds of ansi-terminal are too tight then please send me a patch. No, actually it happens because hspec depends on ansi-terminal-0.5.*. I am cc'ing Simon Hengel, the maintainer of hspec so he is aware of this. Best, Ozgur ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Quickcheck
hi, On 13 November 2012 21:52, gra...@fatlazycat.com wrote: prop_something x y = ...do blah with positive integers == x 0 y 0 quickcheck provides a few nice new types for such cases. try: prop_something (Positive x) (Positive y) = ... this way qc only generates positive numbers, instead of generating and discarding some. hth, -- Ozgur Akgun ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Is there a tool to see reduction steps?
Hi Daryoush, You could add another case to label, importing Debug.Trace: data Tree = Leaf | Node Tree Int Tree deriving Show *label t | trace (show $ label ++ show t) False = undefined* label (Node ln _ rn) ((h:r):rest) = (Node lr h rr, r:r2) where (lr, r1) = label ln rest (rr, r2) = label rn r1 label _ _ = (Leaf, []) lt t = let (r, unused) = label t ([1..]:unused) in r This will output one line per each call to label. Except for one thing: your show function will never actually terminate, if the tree is cyclic. You can fix this by defining your own show function. HTH, Ozgur ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] a parallel mapM?
Hi, On 3 October 2012 19:23, Ryan Newton rrnew...@gmail.com wrote: That said, I don't see a reason for not including a separate version of runParIO :: ParIO a - IO a for non-deterministic computations. It seems really useful! Exactly. I should have been more explicit but that's what I meant about adding another module. You would import Control.Monad.Par.IO and get runParIO + liftIO but NOT runPar. This requires doing a newtype over Par to create the liftIO instance for one and not the other (and preserve Safe Haskell). It's a pain but it's no problem. Both types Control.Monad.Par.Par and Control.Monad.Par.IO.ParIO will expose the same interface (i.e. have instances of the same classes -- ParFuture, ParIVar...), so generic algorithms like parMap will still work for either. -Ryan This sounds like a great idea, I just wanted to ask if anyone is working on it or not? Thanks, Ozgur ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Discovery of unnecessary build-depends
On 28 September 2012 19:29, Jason Whittle ja...@funnelfire.com wrote: Is there a tool available that will tell me if the cabal file for my library or application has any unnecessary build-depends? FWIW, I felt the need for such a tool many times before too. The same tool can also report outdated dependencies, maybe? Cheers, Ozgur ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Printing call site for partial functions
Hi, On 25 April 2012 16:36, Michael Snoyman mich...@snoyman.com wrote: Prelude.head: empty list Recent versions of GHC actually generate a very helpful stack trace, if the program is compiled with profiling turned on and run with -xc. See: http://community.haskell.org/~simonmar/slides/HIW11.pdf(Ironically titled Prelude.head: empty list) HTH, Ozgur ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] adding the elements of two lists
On 29 March 2012 04:34, Richard O'Keefe o...@cs.otago.ac.nz wrote: u f (PS x)= PS $ map f x b f (PS x) (PS y) = PS $ zipWith f x y to_ps x = PS (x : repeat 0) Also see: http://hackage.haskell.org/package/newtype -- Ozgur Akgun ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Are there arithmetic composition of functions?
Hi,
If you are feeling adventurous enough, you can define a num instance for
functions:
{-# LANGUAGE FlexibleInstances #-}
instance Num a = Num (a - a) where
f + g = \ x - f x + g x
f - g = \ x - f x - g x
f * g = \ x - f x * g x
abs f = abs . f
signum f = signum . f
fromInteger = const . fromInteger
ghci let f x = x * 2
ghci let g x = x * 3
ghci (f + g) 3
15
ghci (f+g+2) 2
17
HTH,
Ozgur
On 19 March 2012 16:57, sdiy...@sjtu.edu.cn wrote:
By arithmetic I mean the everyday arithmetic operations used in
engineering.
In signal processing for example, we write a lot of expressions like
f(t)=g(t)+h(t)+g'(t) or f(t)=g(t)*h(t).
I feel it would be very natural to have in haskell something like
g::Float-Float
--define g here
h::Float-Float
--define h here
f::Float-Float
f = g+h --instead of f t = g t+h t
--Of course, f = g+h is defined as f t = g t+h t
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Re: [Haskell-cafe] Are there arithmetic composition of functions?
On 19 March 2012 17:43, David Thomas davidleotho...@gmail.com wrote: The 17 at the end should be 12, or the 2 passed into (f+g+2) should be 3. It was the latter :) Copy/paste error, sorry. Ozgur ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Are there arithmetic composition of functions?
Hi Chris,
On 19 March 2012 17:58, Chris Smith cdsm...@gmail.com wrote:
On Mar 19, 2012 11:40 AM, Ozgur Akgun ozgurak...@gmail.com wrote:
{-# LANGUAGE FlexibleInstances #-}
instance Num a = Num (a - a) where
You don't want (a - a) there. You want (b - a). There is nothing about
this that requires functions to come from a numeric type, much less the
same one.
Thanks for catching this one, you are absolutely correct. I was carried
away by the original post using Float - Float for the example functions.
Cheers,
Ozgur
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[Haskell-cafe] cabal test-suite library recompilation
Hi all, I've recently started to move my tests to use the new cabal test-suite framework. Old setup: The cabal file compiles one library + a few executables. The library contains almost all of the code and exposes the necessary modules for use by the executables. The executables mainly consist of one main file. This way, the library is only compiled once and used multiple times by the executables. Great. One of the executables compile a test runner, and is handled similarly. New setup, using test-suite: I've deleted the executable section for the test runner and added a test-suite section instead. To my surprise, the library is compiled twice now. Hence, it takes twice as long. And it is a clear regression compared to my old setup. While waiting for a build to finish [ :) ], I just wanted to write an email and check if this is intentional or only an oversight. Or maybe a technical limitation for the time being? Thanks, Ozgur ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] cabal test-suite library recompilation
On 13 March 2012 16:22, Antoine Latter aslat...@gmail.com wrote: If your library code and test code are in separate sub-directories and you reference your library as a package dependency for your test then Cabal won't re-build your library. Yay! That was it. Thanks. Somehow I altered the hs-source-dir field while moving from the old setup to the new setup. So just to confirm, the behaviour of the test-suite section is exactly the same as that of executable sections. Cheers, Ozgur ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Prettier pretty-printing of data types?
I prefer pretty-show rather than groom as it's output is hierarchical. http://hackage.haskell.org/package/pretty-show Ozgur On 13 March 2012 22:37, Austin Seipp mad@gmail.com wrote: It's not exactly hierarchical, but Groom most certainly should help with getting much prettier output: http://hackage.haskell.org/package/groom ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Finally, a pure iteratee library that deals with errors
I didn't really look into (enumerators/iteratees/conduits/etc)-land closely enough, but I can say one thing. The code you link to is very easy to understand and see what is going on. This must be a good thing. On 26 February 2012 10:50, Daniel Waterworth da.waterwo...@gmail.comwrote: There's seems to be a growing trend amongst the Haskell community for writing replacements of enumerator. It's shortcomings are well documented, Where can I find a compilation of their shortcomings? Best, Ozgur ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] hackage down
Hackage seems to be down: http://www.downforeveryoneorjustme.com/http://hackage.haskell.org Best, Ozgur ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] how to print out intermediate results in a recursive function?
Hi, There is also this nice trick to use Debug.Trace: merge xs ys | trace (show (xs,ys)) False = undefined -- add this as the first case to merge mergesort xs | trace (show xs) False = undefined -- and this as the first case to mergesort HTH, Ozgur ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] ghc-api Static Semantics?
Hi, I don't know what you actually need, but if haskell-src-exts is an option, it is quite a bit easier to use (definitely easier to understand for me!). Especially when used together with Uniplate. For example, for a given piece of AST one can get all the identifiers used like so: [ x | Ident x - universeBi ast ] Finding where they are bound shouldn't be very hard either. Hope this helps, Ozgur On 23 January 2012 17:33, Christopher Brown cm...@st-andrews.ac.uk wrote: Hi, I was wondering if anyone could tell me if it's possible to get an AST from the ghc-api decorated with static-semantics? In particular, I am interested in use and bind locations for all names in the AST together with the module they are bound, etc. Looking through the online docs, there doesn't seem to be a way to do this. Even if I can tell from the AST where a variable is bound that would be enough, if this is by making all names unique and qualified that would be better than nothing. Hope someone can help, Chris. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Idris
Just by looking at the hackage dependencies, it doesn't look like it has unix-only dependencies. Maybe the Boehm garbage collector? http://www.hpl.hp.com/personal/Hans_Boehm/gc/ Also, Idris has a mailing list, Edwin would be more likely to respond there: http://groups.google.com/group/idris-lang HTH, Ozgur On 20 January 2012 19:15, Ryan Ingram ryani.s...@gmail.com wrote: Has anyone played with Idris (http://idris-lang.org/) at all? It looks interesting, and I'd love to play with it, but unfortunately I only have windows machines up and running at the moment and the documentation seems to imply it only builds on unixy systems. I'm curious how difficult it would be to get a win32 implementation up and running. -- ryan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] GHC exceeding command line length limit with split-objs - and a possible fix
Hi Eugene, I think I did run into this problem before, and had to turn of split-objs temporarily to work around it. I'd appreciate a fix. Best, Ozgur On 11 January 2012 14:14, Eugene Kirpichov ekirpic...@gmail.com wrote: Now my original question remains - is such a change a good idea? (I've already found the place in code where the fix has to be made; should take an hour of work at most) ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] DB vs read/show for persisting large data
On 14 December 2011 15:02, Yves Parès limestr...@gmail.com wrote: The 'derive' package? The problem is that it has a lot of dependencies you maybe don't need if you jut want serialization, plus it relies on TH so it grows both compilation time and executable size. Well you can use the stand alone executable to generate the code for instances and only ship that with your package. No added dependencies at all. Ozgur ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] How to get a file path to the program invoked?
Hi. On 5 December 2011 14:53, dokondr doko...@gmail.com wrote: Main System.Environment.Executable System.FilePath /abc / / / Instead of getting /abc/ I get /. What am I doing wrong? It thinks the second path is an absolute path. Combine two paths, if the second path isAbsolute, then it returns the second. http://hackage.haskell.org/packages/archive/filepath/latest/doc/html/System-FilePath-Posix.html#v:combine HTH, Ozgur ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] cabal install --hyperlink-source ?
On 2 December 2011 16:13, Johannes Waldmann waldm...@imn.htwk-leipzig.dewrote: but I don't see how to pass options from cabal install to cabal haddock (e.g., --hyperlink-source) As it seems, it is not possible. http://stackoverflow.com/questions/2472630/enable-hyperlink-source-for-cabal-install -- Ozgur ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Using QuickCheck to test against a database
Hi! This looks cool indeed. On 2 December 2011 00:02, Oliver Charles haskell-c...@ocharles.org.ukwrote: [snip] You have to remember to apply all of the states of your arbitrary instances, which is a pain, and guaranteed to be missed. Why can't you define a helper function which runs the initDb action while picking the entity? Something like: pickDB = do DBState act e - pick arbitrary; act; return e (placing calls to monadicIO and run appropriately, I am not familiar enough with the monadic API) Secondly, the initDb action is sensitive to the order actions are sequenced. Do you mean with respect to other initDb actions? Why is this? I thought you were using QuickCheck in order not to assume things about the state of the DB and that the necessary state is prepared solely by running the initDb action. Is this not the case then? Cheers, Ozgur ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] ANN: Netwire 2.0.0
Hi Ertugrul, Compilation problems here: cabal install netwire [ 7 of 22] Compiling Control.Wire.Prefab.Simple ( Control/Wire/Prefab/Simple.hs, dist/build/Control/Wire/Prefab/Simple.o ) Control/Wire/Prefab/Simple.hs:15:7: Ambiguous occurrence `force' It could refer to either `Control.Wire.Prefab.Simple.force', defined at Control/Wire/Prefab/Simple.hs:41:1 or `Control.DeepSeq.force', imported from Control.DeepSeq at Control/Wire/Prefab/Simple.hs:24:1-22 cabal: Error: some packages failed to install: netwire-2.0.0 failed during the building phase. The exception was: ExitFailure 1 This build was trying to use deepseq-1.2.0.1. It builds fine with deepseq-1.1.0.2 though. Best, Ozgur ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] ANN: Netwire 2.0.0
On 14 November 2011 16:33, Ertugrul Soeylemez e...@ertes.de wrote: It should be fixed now. Thanks for your report! Fixed indeed. Thanks. Ozgur ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Libraries to compare trees?
Hi. On 27 October 2011 13:49, dokondr doko...@gmail.com wrote: Please advise on Haskell libraries to compare trees in textual representation. I need to compare both structure and node contents of two trees, find similar sub-trees, and need some metric to measure distance between two trees. This might help: http://hackage.haskell.org/package/gdiff-1.0 Best, Ozgur ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Parsec and Text
Hi. See the following for the recent announcement: http://permalink.gmane.org/gmane.comp.lang.haskell.general/18972 On 8 October 2011 18:37, Yves Parès limestr...@gmail.com wrote: Is there a package that allows parsing Text with parsec, ... HTH, Ozgur ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Really Simple explanation of Continuations Needed
Hi. On 1 October 2011 11:55, Yves Parès limestr...@gmail.com wrote: BTW Heinrich, the evalState (sequence . repeat . State $ \s - (s,s+1)) 0 at the end doesn't work anymore. It should be replaced by : evalState (sequence . repeat . StateT $ \s - Identity (s,s+1)) 0 Or equivalently: evalState (sequence . repeat . state $ \s - (s,s+1)) 0 Ozgur ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Fwd: problem with cabal install MissingH-1.1.1.0
Ooops, apparently I forgot to reply to the list. Sorry. -- Forwarded message -- From: Ozgur Akgun ozgurak...@gmail.com Date: 22 September 2011 16:49 Subject: Re: [Haskell-cafe] problem with cabal install MissingH-1.1.1.0 To: Mariano Cortesi mcort...@gmail.com Hi Mariano. On 22 September 2011 12:48, Mariano Cortesi mcort...@gmail.com wrote: I'm with mac OS X lion, ghc version 7.2.1 and when a i try to install MissingH version 1.1.1.0 it fails with [24 of 47] Compiling Data.BinPacking ( src/Data/BinPacking.hs, dist/build/Data/BinPacking.o ) src/Data/BinPacking.hs:45:6: Illegal datatype context (use -XDatatypeContexts): (Num size, This is weird, because on OS X Lion, and with the following versions, it doesn't fail for me: The Glorious Glasgow Haskell Compilation System, version 7.2.1 cabal-install version 0.10.2 using version 1.12.0 of the Cabal library Nevertheless, you can try the following to do what cabal asks you to do: cabal install --ghc-option=-XDatatypeContexts Which will give a warning, but should succeed anyway. Hope this helps, Ozgur -- Ozgur Akgun ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] cabal-install to produce a dependency tree
Dear Cafe, What would be the easiest way of generating the following output, given a package name optionally with additional constraints? $- foo X 3 X 3 depends on A-2.2, B-1.0, C-1.2 A-2.2 depends on D-1.2.3 ... I assume cabal-install internally does this anyway while creating the installation plan, so is there an easy way to get this info out of cabal install? Thanks, Ozgur ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] type profiling not helpful
Cafe, Using prog +RTS -M1G -hy for my program prog, I generate a heap profile as documented in [1]. There is one big block in the output graph labelled with * though, which is not very helpful. The star character isn't even mentioned in the documentation, I wonder what it represents. Thanks in advance, [1] http://www.haskell.org/ghc/docs/latest/html/users_guide/prof-heap.html#rts-options-heap-prof -- Ozgur Akgun ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Unexpected Typeable behaviour; Prelude.undefined
Hi Philip, On 28 August 2011 23:44, Philip Holzenspies p...@st-andrews.ac.uk wrote: import Data.Typeable data MyADT m = MyADT (m ()) instance (Typeable1 m, Monad m) = Typeable (MyADT m) where typeOf t@(MyADT _) = mkTyCon MyADT `mkTyConApp` [typeOf1 ((return :: Monad m = MyADT m - m (MyADT m)) t)] IIRC, typeOf is supposed to work with undefined as the argument. Try: typeOf (undefined :: Int) See: http://hackage.haskell.org/packages/archive/base/latest/doc/html/Data-Typeable.html#v:typeOf I think the undefined is merely because the pattern matching you use in the instance declaration fails. Hope this helps, Ozgur ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Haddock chokes on function arguments
Hi Arnaud, On 25 August 2011 15:44, Arnaud Bailly arnaud.oq...@gmail.com wrote: But then, why is it documented the other way ? It isn't, as far as I can see. Are we both looking at the same place, namely section 3.2.3? -- Ozgur Akgun ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] haskell-src-exts should depend on happy
Hi, cabal installing haskell-src-exts fails, because of an unlisted dependency to the happy executable. The following succeeds: cabal install happy; cabal install haskell-src-exts Thanks, Ozgur ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] *GROUP HUG*
Evan, On 24 May 2011 19:57, Evan Laforge qdun...@gmail.com wrote: On the catMaybes thing, I have a function 'mapMaybe = Maybe.catMaybes . map'. I turns out I only ever used catMaybes after mapping a Maybe function, so I hardly ever use catMaybes anymore. I suppose it should have been maybeMap for consistency with concatMap. Just wanted to point out, that function is already defined in Data.Maybe: http://hackage.haskell.org/packages/archive/base/latest/doc/html/Data-Maybe.html#v:mapMaybe Hugs :) Ozgur ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Hash table constructors return table in IO Monad. Why?
On 12 May 2011 20:59, michael rice nowg...@yahoo.com wrote: HashTable doesn't do it. Neither does Map. Was I dreaming? I suppose you could implement this functionality on top of either. HTH, Ozgur ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Reformatter for Show
Hi Alexey, On 2 May 2011 21:01, Alexey Khudyakov alexey.sklad...@gmail.com wrote: My question is there any tool for reformatting result of show so it could be read by human beings? http://hackage.haskell.org/package/pretty-show Just use ppShow, instead of show. Hope this helps, Ozgur ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Trouble with currying and uncurrying...
On 25 April 2011 14:11, Angel de Vicente ang...@iac.es wrote: curry :: ((a,b) - c) - (a - b - c) is the same as: curry :: ((a,b) - c) - a - b - c HTH, Ozgur ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] 64 bit generic link warning on every compile
The -read_only_relocs flag is no longer used on OS X 64, which eliminates some warnings. http://www.haskell.org/ghc/docs/7.0.3/html/users_guide/release-7-0-3.html HTH, Ozgur On 16 April 2011 03:47, Andrew Pennebaker andrew.penneba...@gmail.comwrote: GHC 7 compiles fine, but there's an additional warning during linking. $ system_profiler SPSoftwareDataType | grep System Version System Version: Mac OS X 10.6.7 (10J869) $ ghc --version The Glorious Glasgow Haskell Compilation System, version 7.0.2 $ cat hello.hs #!/usr/bin/env runhaskell module Main where main :: IO () main = putStrLn Hello World $ ghc --make hello.hs [1 of 1] Compiling Main ( hello.hs, hello.o ) Linking hello ... ld: warning: -read_only_relocs cannot be used with x86_64 $ ./hello Hello World Cheers, Andrew Pennebaker www.yellosoft.us ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe -- Ozgur Akgun ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Fucntion composing
In addition to what others have said, you could use pointfree[1] to do this automagically! pointfree h x y = (g 0 (f x y)) h = (g 0 .) . f [1] http://hackage.haskell.org/package/pointfree On 11 April 2011 10:22, Adam Krauze ajschy...@mac.com wrote: Hello, as I am newbie to Haskell and my introductory question is: given functions say f and g with type signatures f :: (Num a) = [a] - [a] - [(a,a)] // f takes two lists and zips them into one in some special way g :: (Num a) = a - [(a,a)] - [a] // g using some Num value calculates list of singletons from list of pairs of course g 0 :: (Num a) = [(a,a)] -[a] now I want to create function h :: (Num a) = [a] - [a] - [a] in such way that (g 0) consumes output of f. But when I try Prelude :t (g 0).f I get an error: interactive:1:9: Couldn't match expected type `[(a0, a0)]' with actual type `[a1] - [(a1, a1)]' Expected type: [a1] - [(a0, a0)] Actual type: [a1] - [a1] - [(a1, a1)] In the second argument of `(.)', namely `f' In the expression: (g 0) . f In pointfull representation it works well Prelude let h x y = (g 0 (f x y)) How to do pointfree definition of h? Ajschylos. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe -- Ozgur Akgun ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] parsec - source position information
Hi, Is there a way to get source position[1] information from parsec while defining a parser? It surely knows about source positions, as they are used while reporting a parsing error. data Identifier = Identifier String SourcePos pIdentifier :: Parser Identifier pIdentifier = do pos - ?? s - pString return (Identifier s pos) [1] http://hackage.haskell.org/packages/archive/parsec/3.0.0/doc/html/Text-Parsec.html#t:SourcePos Thanks in advance, Ozgur ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] parsec - source position information
Thanks! On 7 April 2011 16:27, Christopher Done chrisd...@googlemail.com wrote: On 7 April 2011 17:22, Ozgur Akgun ozgurak...@gmail.com wrote: Is there a way to get source position[1] information from parsec while defining a parser? It surely knows about source positions, as they are used while reporting a parsing error. http://hackage.haskell.org/packages/archive/parsec/3.0.0/doc/html/Text-Parsec-Prim.html#v:getPosition http://hackage.haskell.org/packages/archive/parsec/3.0.0/doc/html/Text-Parsec-Prim.html#v:getPosition -- Ozgur Akgun ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Question on a common pattern
See this thread: http://www.haskell.org/pipermail/haskell-cafe/2010-October/084291.html On 14 March 2011 15:48, tsuraan tsur...@gmail.com wrote: In my code, I'm doing this quite a lot: x - someIO case x of Opt1 - ... Having a line for extracting the value from the IO (or STM) and then acting on the value seems unnatural. Is there a more concise way to do this? This code: case someIO of Opt1 - ... Doesn't work, but is there something like that, that is valid? ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe -- Ozgur Akgun ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Learn You a Haskell for Great Good - a few doubts
On 4 March 2011 09:47, Karthick Gururaj karthick.guru...@gmail.com wrote: I'm not able to still appreciate the choice of the default ordering order, I don't know if this will help you appreciate the default or not, but just to say this default is concordant with the auto-derived Ord instances. data Tuple3 a b c = Tuple3 a b c deriving (Eq,Ord,Show) ghci sort [Tuple3 1 2 4, Tuple3 1 2 3, Tuple3 2 1 1, Tuple3 1 3 5] [Tuple3 1 2 3,Tuple3 1 2 4,Tuple3 1 3 5,Tuple3 2 1 1] ghci sort [(1,2,4), (1,2,3), (2,1,1), (1,3,5)] [(1,2,3),(1,2,4),(1,3,5),(2,1,1)] No surprises here. Just another place where we have the lexicographic ordering by default. HTH, -- Ozgur Akgun ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Noob question about list comprehensions
On 16 February 2011 09:19, Tako Schotanus t...@codejive.org wrote: I wondered if there was a way for a guard in a list comprehension to refer to the item being produced? I'm just wondering about this very specific case Then, the answer is no. As others have noted, let binding is the way to go. Ozgur ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] combined parsing pretty-printing
Tillmann, I've been looking into you packages, very neat ideas and a nice implementation really. I've already implemented a toy example and it worked great. Now I am trying to use your library in a more serious piece of code, and I've realised that defineIsomorphisms doesn't support record constructors. To be precise, you handle the case for NormalC in the code, however you do not handle RecC. I don't think this will be a difficult thing to add. Is there any reason for you not to support RecC? Best, 2011/1/26 Tillmann Rendel ren...@informatik.uni-marburg.de Hi Ozgur, Ozgur Akgun wrote: I can write (separately) a parser and a pretty-printer [...] Is there any work to combine the two? Brent Yorgey wrote: Maybe take a look at Invertible Syntax Descriptions: Unifying Parsing and Pretty Printing by Tillmann Rendel and Klaus Ostermann from last year's Haskell Symposium: http://www.informatik.uni-marburg.de/~rendel/unparse/ It's a beautiful paper, and perhaps the code will work for you (although it's too bad it's not on Hackage). Indeed, I started this project for exactly the reason Ozgur describes: I needed to duplicate a lot of information between parsers and pretty printers and was annoyed about it. With invertible syntax descriptions, I now write a single program, which looks like a combinator parser (think Parsec), but can work as a pretty printer, too. I just uploaded the code from the paper (and some additional combinators) to Hackage: http://hackage.haskell.org/package/partial-isomorphisms http://hackage.haskell.org/package/invertible-syntax I use this code for the implementation of some very small languages (think lambda calculus). This works fine. I haven't really tried it for larger languages, but we have two students here in Marburg implementing a parser for Java using the library, so we are going to have experience with larger languages in a few weeks (months?). If you give it a try, I would be happy to receive success stories, bug reports, patches, feature requests etc. I want to keep working on this, and I am open for suggestions. Tillmann ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe -- Ozgur Akgun ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] combined parsing pretty-printing
Great! That was pretty fast :) Are you going to update invertible-syntax to use partial-isomorphisms-0.2? 2011/2/5 Tillmann Rendel tillm...@rendel.net Hi Ozgur, Ozgur Akgun wrote: I've already implemented a toy example and it worked great. Now I am trying to use your library in a more serious piece of code, and I've realised that defineIsomorphisms doesn't support record constructors. To be precise, you handle the case for NormalC in the code, however you do not handle RecC. I don't think this will be a difficult thing to add. Is there any reason for you not to support RecC? No reason at all. I just generalized the Template Haskell macros. They now support: * newtypes * infix constructors * record constructors Infix constructors are only support by constructorIso, though, not by defineIsomorphisms, because I can't think of a good automatic naming scheme. Suggestions welcome. The code is on hackage. There are still some constructors which are not supported: constructors of GADTs as well as data or newtype instances, and constructors with existentials. I would need to think about typing issues before supporting these. Tillmann -- Ozgur Akgun ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Inheritance and Wrappers
On 3 February 2011 02:35, Brandon Moore brandon_m_mo...@yahoo.com wrote: Here's one thing to consider: Can you write a function f :: (Data a) = a - String f x = termTag x It would seem the Data a = Term a instance justifies this function, and it will always use the default instance. Now, what happens if f is applied to a value of some type T which is an instance of Data, but has a custom Term instance? Great point, thanks! I guess somehow you shouldn't be allowed to write that function f. I need to think about this one. -- Ozgur ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Haskell Functions
On 3 February 2011 18:33, Manolache Andrei-Ionut andressocrate...@yahoo.com wrote: first this is the curent code :http://pastebin.com/UPATJ0r There is no code on that page. (It has expired, probably?) -- Ozgur Akgun ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Reader monad wrapping State monad
On 3 February 2011 19:18, michael rice nowg...@yahoo.com wrote: but how do I get the constant a from the Reader monad? http://hackage.haskell.org/packages/archive/transformers/latest/doc/html/Control-Monad-Trans-Reader.html#v:ask You also need to change the type to use ReaderT. -- Ozgur Akgun ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Haskell Functions
(CCing haskell-cafe again) Is this an homework question? On 3 February 2011 20:30, Manolache Andrei-Ionut andressocrate...@yahoo.com wrote: http://pastebin.com/GxQBh3hx http://pastebin.com/GxQBh3hx --- On *Thu, 2/3/11, Ozgur Akgun ozgurak...@gmail.com* wrote: From: Ozgur Akgun ozgurak...@gmail.com Subject: Re: [Haskell-cafe] Haskell Functions To: Manolache Andrei-Ionut andressocrate...@yahoo.com Cc: haskell-cafe@haskell.org Date: Thursday, February 3, 2011, 10:59 AM On 3 February 2011 18:33, Manolache Andrei-Ionut andressocrate...@yahoo.comhttp://mc/compose?to=andressocrate...@yahoo.com wrote: first this is the curent code :http://pastebin.com/UPATJ0r There is no code on that page. (It has expired, probably?) -- Ozgur Akgun -- Ozgur Akgun ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Inheritance and Wrappers
On 1 February 2011 11:41, John Lato jwl...@gmail.com wrote: The important point is that this declares an AbGroup instance for every type, not just types with Num instances. So, is there a way to declare an AbGroup instance for the types with num instances only? Thanks, Ozgur ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Inheritance and Wrappers
OK, what about this as a use case then. I want to create a type class 'Term'
with only one function in it. The function returns a 'termTag' which labels
the *kind* of a value in a DSL.
class Term a where
termTag :: a - String
A user of this type-class can happily provide an instance without any other
type class requirement. However, I want those types which are instances of
Data to be an instance of Term automatically. On top of that, I don't want
to stop the user from creating a special instance for their data type.
I want to be able to write the following instance to accomplish that:
instance Data t = Term t where
termTag = show . toConstr
And if the user wants to write a more specific instance, they should be
welcome to do so:
instance Term UserDT where
termTag (...) = ...
I am not very much interested in the technical details about how things
currently are, I am more interested in a discussion about why (if?) this
would be considered a *design flaw*?
Best,
On 1 February 2011 12:18, Stephen Tetley stephen.tet...@gmail.com wrote:
On 1 February 2011 11:47, Ozgur Akgun ozgurak...@gmail.com wrote:
So, is there a way to declare an AbGroup instance for the types with num
instances only?
No - as Henning says its then no more useful than simply a function:
add :: (Num u) = a - a - a
add = (+)
'Overarching instances' i.e. classes with one implementation are a
design flaw, not a virtue [*] so this hypothetical extension isn't
welcome...
{-# LANGUAGE OverarchingInstances #-}
[*] Of course, there might be some valid cases for things in Oleg
Kiselyov's typecast style, but modelling numericals doesn't look like
one of them.
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[Haskell-cafe] combined parsing pretty-printing
Dear Café, I working on a DSL represented by a algebraic data type with many constructors. I can write (separately) a parser and a pretty-printer for it, and I am doing so at the moment. However, this way it feels like repeating the same information twice. Is there any work to combine the two? Best, Ozgur ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Why is Haskell flagging this?
see also: http://hackage.haskell.org/packages/archive/mtl/latest/doc/html/Control-Monad-State-Lazy.html#v:state On 22 December 2010 20:02, Ryan Ingram ryani.s...@gmail.com wrote: Interesting. In that case, state f = StateT $ \s - Identity (f s) allows state to replace State in that code. Ozgur ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] the beginning of the end
On 5 December 2010 20:22, Brandon S Allbery KF8NH allb...@ece.cmu.eduwrote: On 12/5/10 15:07 , Andrew Coppin wrote: you actually cannot do something as trivial as follow a conversation You can, just not via the web site. I do it in Tweetdeck all the time. You can also do it via the website, sort of. If a tweet is a reply to another one, there is a in reply to link right under the tweet. I guess other client applications (like tweetdeck) use this link to create a conversation view. I suppose, it is quite similar to what happens with e-mail. -- Ozgur Akgun ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Hackage down?
http://downforeveryoneorjustme.com/http://hackage.haskell.org -- Ozgur Akgun ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Offer to mirror Hackage
This is a very generous offer. However, I must say I like the following idea more: http://www.reddit.com/r/haskell/comments/efw38/reminder_hackagehaskellorg_outage_tomorrow_due_to/c17u7nk On 4 December 2010 16:31, Dan Knapp dan...@gmail.com wrote: With Hackage down, now seemed like a good time to push this issue again. It's such an important site to us that it's really rather a shame there are no mirrors of it. I have a personal-and-business server in a data center in Newark, with a fair chunk of bandwidth, which I'd like to offer for a permanent mirror. Is there interest in this? Who do I need to talk to for it to happen? Strategy-wise, I think the best approach is round-robin DNS, since that's transparent to the end user - everything would still appear at the URL it's at now, but behind-the-scenes magic would let things keep working when one or the other site is down. I haven't personally set up such a system before but I'm willing to take on the burden of figuring it out. So I have a better idea of what I'm signing up for, can anyone tell me how much disk space and how much bandwidth per month Hackage uses? I have a fair chunk of both, as I say, but I'd like to know in advance to ensure that things go smoothly. As for what I'd want in return for this, really nothing. I wouldn't say no to an unobtrusive mention somewhere on the site, but I'd be happy just knowing I'd given something back to the Haskell community, which has given a lot to me. -- Dan Knapp An infallible method of conciliating a tiger is to allow oneself to be devoured. (Konrad Adenauer) ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe -- Ozgur Akgun ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Type Directed Name Resolution
On 11 November 2010 01:19, Richard O'Keefe o...@cs.otago.ac.nz wrote: I'm not sure that it is desirable to have many records in the same module in the first place. Amongst other reasons, http://www.haskell.org/haskellwiki/Mutually_recursive_modules -- Ozgur Akgun ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] ghc dump the code for derived instances
Café, Is there a way to make GHC dump the code for auto-derived type class instances, say for Show, Eq and such? Thanks, Ozgur ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] ghc dump the code for derived instances
Thanks! On 11 November 2010 14:52, Daniel Fischer daniel.is.fisc...@web.de wrote: On Thursday 11 November 2010 15:27:09, Ozgur Akgun wrote: Café, Is there a way to make GHC dump the code for auto-derived type class instances, say for Show, Eq and such? -ddump-deriv Thanks, Ozgur -- Ozgur Akgun ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Type Directed Name Resolution
I still don't know whether I like this idea or not, but here is the simplest
definition I can think of about what it promises.
Using TDNR, it will be possible to write the following code:
data Foo = Foo { name :: String }
data Bar = Bar { name :: String }
getName :: Either Foo Bar - String
getName (Left f) = name f
getName (Right b) = name b
However, currently you cannot: Multiple declarations of 'name'
There are basically two things you can do to solve this problem.
- Use different names for your functions, a la fooName, barName. This
clutters up your code, and sometimes you may not have access to that part of
the code.
- Define these 2 data types in different modules and import qualified, a la
Foo.name, Bar.name. One might still think this clutters up your code.
In any case, as a programmer you need to resolve which function to use
depending on types while defining 'getName'. However compiler has enough
information to automate this decision for you. This is not a way to do
polymorphism, this is merely a way to allow programmers define more than one
function with the same name, but different types.
This kinda sounds like what java people think polymorphism is :P
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Re: [Haskell-cafe] Type Directed Name Resolution
On 10 November 2010 10:56, Ozgur Akgun ozgurak...@gmail.com wrote:
Using TDNR, it will be possible to write the following code:
data Foo = Foo { name :: String }
data Bar = Bar { name :: String }
getName :: Either Foo Bar - String
getName (Left f) = name f
getName (Right b) = name b
However, currently you cannot: Multiple declarations of 'name'
Oh by the way, TDNR doesn't only work for record names, yet its use for
record names is an important motivation. This was just an example. I don't
want to cause any confusion while trying simplify things.
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Re: [Haskell-Cafe] Parsing bytestream
If we change the code a bit, data MyAction = A1 Word8 | A2 Word16 a,b :: Get MyAction a = A1 $ getWord8 b = A2 $ getWord16be listOfActions :: [Get MyAction] listOfActions = [a,b,a] Now, we know how to execute the list of actions, and get the output as list. Using the following guys: sequence :: Monad m = [m a] - m [a] runGet :: Get a - ByteString - a Best, Ozgur ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Compiler constraints in cabal
AFAIK, the way to do this is putting constraints on the base package. On 5 November 2010 14:59, Reiner Pope reiner.p...@gmail.com wrote: Hi, I have a library, hmatrix-static, on Hackage. Version 0.3 (the current version) compiles with ghc-6.12. Let's say I want to upgrade my library using new features in ghc-7.0, and then release these upgrades as version 0.4. Is there any way to state in my cabal file that this new version will no longer compile under ghc-6.12? The reason I would like to state this is so that a user with ghc-6.12 can do 'cabal install hmatrix-static' (or do a cabal install of a program depending on hmatrix-static) and see that cabal will install version 0.3 rather than attempt to install version 0.4 and fail. Thanks for your help. Reiner ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe -- Ozgur Akgun ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Parsing workflow
On 1 November 2010 22:18, Andrew Coppin andrewcop...@btinternet.com wrote: I vaguely recall somebody mentioning a parser library on Hackage where try is the default behaviour and you turn it off explicitly, rather than turning it on explicitly. Apparently this is much more intuitive. But unfortunately I can't remember what the hell the library was... polyparse, is it? from http://code.haskell.org/~malcolm/polyparse/docs/index.html#what If you have only ever used the parsec combinators before, then you might be pleasantly surprised by polyparse: all of the same functionality is available, but it removes the confusion that all too commonly arises from a failure to use parsec's try combinator correctly. Ambiguous grammars often fail to be compositional in parsec, and it can be a black art guessing where to introduce a try to fix it. In contrast, polyparsers are by default fully compositional. It is possible to improve their efficiency (and the accuracy of error messages) by inserting commits (which are the dual of try), but it is not necessary for writing a correct parser, and furthermore, it is usually obvious where it can be beneficial to add a commit. Ozgur ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Parsing workflow
I don't know if you've already used it, but Parsec includes some kind of a lexer through the Languagehttp://hackage.haskell.org/packages/archive/parsec/3.1.0/doc/html/Text-Parsec-Language.htmland Tokenhttp://hackage.haskell.org/packages/archive/parsec/3.1.0/doc/html/Text-Parsec-Token.htmlmodules. You can start by having a look at the makeTokenParserhttp://hackage.haskell.org/packages/archive/parsec/3.1.0/doc/html/Text-Parsec-Token.html#v:makeTokenParser function. On 31 October 2010 15:11, Nils Schweinsberg m...@n-sch.de wrote: Hi! I'm having a really hard time to write a correct parser for a small language I've developed. I have been trying to write a parser using parsec, but always get a lot of error messages like unexpected \n, expected ..., new-line or... when trying to run the parser. Then I read about the happy parser and really liked the separation of lexing the text into tokens and parsing the actual logic behind those tokens. Since I couldn't get familiar with the lexer alex I gave up on the alex-happy-approach again and went back to parsec. But with that lexer-parser idea on my mind, my parser currently looks a lot like a lexer. So I came up with the idea of using a combination of parsec and happy, where I generate a list of tokens for my text via parsec and analyse it with happy. My questions would be: - Is this a valid approach? - What is your workflow on parsing complex data structures? - What about performance? Since my project is going to be an interpreted language parsing performance might be interesting aswell. I've read that happy is in general faster than parsec, but what if I combine both of them as I said above? I guess that parsing a simple list of tokens without any nested parser structures would be pretty fast? - Do you have any other ideas on how to improve my parser? - What are your general thoughts on happy vs. parsec? Thanks for any replies, Nils ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe -- Ozgur Akgun ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Parsing workflow
On 31 October 2010 16:15, Nils Schweinsberg m...@n-sch.de wrote: This is exactly what gives me headaches. It's hard to tell where you need try/lookAhead and where you don't need them. And I don't really feel comfortable wrapping everything into try blocks... I always thought this was an obvious decision: when combining 2 parsers `a` and `b` (i.e. a | b), if parser `a` fails without consuming any input do not wrap it in a try, otherwise do. Am I missing something? Ozgur ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Generic traversals for GADTs
Café, SYB-style libraries (and especially Uniplate) make it very easy to run generic traversals (queries/transformations) on ADTs. data Expr = ... x :: Expr f :: Expr - Expr transform :: (Expr - Expr) - Expr - Expr transform f x :: Expr -- applies f to x (and its children) in a bottom-up manner Uniplate is very powerful and doesn't require any hand written type-class instances to get going reasonably efficiently. I can simply re-implement the functionality of Uniplate myself, modulo requiring hand-written instances. (I didn't want to go into that road, since I don't need it for this argument.) I did this exercise, because I wanted to understand why we don't have similar generic traversal libraries for GADTs. And, it didn't take long :) I can post my trials but they are really baby steps and they wouldn't be helpful. My question is: Considering how useful generic traversal libraries and GADTs are, has anybody tried implementing a generic traversal library (like Uniplate or similar) for GADTs? Is it a hard (or impossible, or not efficient, or problematic in some other way) thing to implement, or is it just not a requirement for anyone else? Best, Ozgur ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Decoupling type classes (e.g. Applicative)?
On 29 October 2010 14:35, Dominique Devriese dominique.devri...@cs.kuleuven.be wrote: I have a problem with the design of the Applicative type class Sorry for going a bit off-topic, but every-time I see someone complaining about such things, I remember this proposal: http://repetae.net/recent/out/classalias.html Just wanted to say, wouldn't it be nice? :) Best, Ozgur ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Finite but not fixed length...
Jonas, 2010/10/13 Jonas Almström Duregård jonas.dureg...@chalmers.se (++) :: Finite s1 a - Finite s2 a - Finite (S (Plus s1 s2)) a (++) (Finite a) (Finite b) = Finite $ a Prelude.++ b infixr 5 ++ Why do you have the S in the return type of Finite.++ ? Ozgur ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] ghci - always show types
Cafe, Just a quick question. Either I am hallucinating or there was a way of saying ghci to always show types. It was working as if you typed :t it after every line of input. Sorry, I searched but couldn't find the option via google. Hope someone here knows/remembers what I am talking about. Best, Ozgur ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] ghci - always show types
On 13 October 2010 17:03, Christopher Done chrisd...@googlemail.com wrote: Options for ':set' and ':unset': +rrevert top-level expressions after each evaluation +sprint timing/memory stats after each evaluation +tprint type after evaluation See :help to get this display. Thanks! Ozgur ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Re-order type (flip map)
On 10 October 2010 22:32, Johannes Waldmann waldm...@imn.htwk-leipzig.dewrote: Oh, and while we're at it - are there standard notations for forward function composition and application? I mean instead of h . g . f $ x I'd sometimes prefer x ? f ? g ? h but what are the ? While asking you use the same symbol for function composition, and something like inverse function application. I don't think there exists an operator ?, such that h . g . f $ x is equivalent to x ? f ? g ? h. But you can simply define an inverse function application like the following and have a close enough alternative, ($$) :: a - (a - b) - b ($$) = flip ($) infixl 5 $$ Now the following two expression are identical, I suppose: h . g . f $ x x $$ f . g . h Cheers, Ozgur ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Re-order type (flip map)
No, wrong. I am speaking nonsense here. Of course one also needs to define a *forward* function composition operator to get the effect you originally wanted. My point was: you need to find/define two operators, not just one. That still holds :) Best, On 10 October 2010 23:47, Ozgur Akgun ozgurak...@gmail.com wrote: On 10 October 2010 22:32, Johannes Waldmann waldm...@imn.htwk-leipzig.dewrote: Oh, and while we're at it - are there standard notations for forward function composition and application? I mean instead of h . g . f $ x I'd sometimes prefer x ? f ? g ? h but what are the ? While asking you use the same symbol for function composition, and something like inverse function application. I don't think there exists an operator ?, such that h . g . f $ x is equivalent to x ? f ? g ? h. But you can simply define an inverse function application like the following and have a close enough alternative, ($$) :: a - (a - b) - b ($$) = flip ($) infixl 5 $$ Now the following two expression are identical, I suppose: h . g . f $ x x $$ f . g . h Cheers, Ozgur -- Ozgur Akgun ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Lambda-case / lambda-if
For what it's worth, after all this discussion my rather cheeky preference is as follows: Instead of introducing more specialised syntax, remove both existing special syntaxes for if and case, and introduce multi-clause support for lambdas! Cheers! On 2 October 2010 19:23, Max Bolingbroke batterseapo...@hotmail.com wrote: Hi Cafe, I implemented the proposed Haskell' feature lambda-case/lambda-if [1] during the Haskell Implementors Workshop yesterday for a bit of fun. The patches are online [2, 3]. The feature is demonstrated in this GHCi session: $ inplace/bin/ghc-stage2 --interactive -XLambdaCase GHCi, version 7.1.20101002: http://www.haskell.org/ghc/ :? for help Loading package ghc-prim ... linking ... done. Loading package integer-gmp ... linking ... done. Loading package base ... linking ... done. Loading package ffi-1.0 ... linking ... done. Prelude (if then Haskell else Cafe) False Cafe Prelude (case of 1 - One; _ - Not-one) 1 One Prelude :q Do you like this feature and think it would be worth incorporating this into GHC? Or is it too specialised to be of use? If there is enough support, I'll create a ticket and see what GHC HQ make of it. Max [1] http://hackage.haskell.org/trac/haskell-prime/ticket/41 [2] http://www.omega-prime.co.uk/files/LambdaCase-Testsuite.patch [3] http://www.omega-prime.co.uk/files/LambdaCase-Compiler.patch ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe -- Ozgur Akgun ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Haskell Helper
On 4 October 2010 23:10, c8h10n4o2 asaferibei...@ymail.com wrote: And why b - between (char ',') (char '=') (sepBy alphaNum (char ',') ) does not return [String] ? alphaNum :: Parser Char sepBy :: Parser a - Parser sep - Parser [a] sepBy alphaNum sepP :: Parser [Char] or Parser String but not Parser [String] between :: Parser open - Parser close - Parser a - Parser a between openP closeP (sepBy alphaNum sepP) :: Parser String Hope this helps, Ozgur ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Haskell Helper
On 4 October 2010 23:54, c8h10n4o2 asaferibei...@ymail.com wrote: By the way, there is a parser that returns [String] for my case? If you are trying to parse strings (of alphaNum's) separated by commas, you can use many alphaNum (or many1 alphaNum depending on what you want) instead of simply using alphaNum. The type of the complete parser will then be Parser [String]. alphaNum :: Parser Char alphaNums :: Parser String alphaNums = many alphaNum alphaNums1 :: Parser String alphaNums1 = many1 alphaNum Ozgur ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Lambda-case / lambda-if
On 2 October 2010 19:33, Henning Thielemann lemm...@henning-thielemann.dewrote: On Sat, 2 Oct 2010, Max Bolingbroke wrote: ... lambda-case/lambda-if ... Nice! Concerning if-then-else I would more like to see an according function to go to Data.Bool, then we won't need more syntactic sugar like if-then-else. However the lambda-case would be useful for me. And I was just reading this entry in the wiki: http://www.haskell.org/haskellwiki/If-then-else Best, Ozgur ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Inverse of HaskellDB
OK, I am rephrasing it a bit then :) I definitely don't think this would be trivial to implement. However, I'd expect a decent solution to this problem, not to have special combinators to describe relations between data types, but let the user model their data using plain haskell data types, and infer the associated table structure just by looking at the data types. I'll give this a harder thought once I find the time. There is the huge barrier of TH, stopping me from playing with things like this. Anyway, have fun! :) On 29 September 2010 10:41, Chris Eidhof ch...@eidhof.nl wrote: On 28 sep 2010, at 17:33, Ozgur Akgun wrote: How do you define relationships between data types? Well, why is it any different from other fields? From one of your examples [1], I'd expect you to have a list of questions in the Quiz data type, and if necessary, a quiz field in the Question data type. This might be a bit tricky but certainly achievable [2]. This is really tricky. For example, consider storing a large tree in the database: data Tree = Node Int Tree Tree | Leaf Int This means you need to read the entire tree from the database. Or consider cyclic datastructures (such as the example you gave). How do you store this? The only way to inspect this is using a library like data-reify [1]. I think the problem might be a bit harder than you suspect. Another way to solve it is using Sebastiaan Visser's framework, described in his paper [2], but that's also rather complicated. -chris [1]: http://hackage.haskell.org/package/data-reify [2]: http://github.com/downloads/sebastiaanvisser/msc-thesis/wgp10-genstorage.pdf -- Ozgur Akgun ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Inverse of HaskellDB
How do you define relationships between data types?
Well, why is it any different from other fields? From one of your examples
[1], I'd expect you to have a list of questions in the Quiz data type, and
if necessary, a quiz field in the Question data type. This might be a bit
tricky but certainly achievable [2].
Something like the following:
data Quiz = Quiz {
description :: String,
subject :: String,
questions :: [Question]
} deriving (Show, Read)
data Question = Question {
title :: String,
choiceA :: String,
choiceB :: String,
choiceC :: String,
quiz:: Quiz
} deriving (Show, Read)
[1] http://github.com/chriseidhof/persist/blob/master/examples/Model.phs
[2] http://www.haskell.org/haskellwiki/Tying_the_Knot
On 28 September 2010 16:13, Chris Eidhof ch...@eidhof.nl wrote:
Hey Jonathan,
I've done some work on this. The hard part is defining relationships
between datatypes: how do you model this in Haskell? I've some code on
github: http://github.com/chriseidhof/persist, you might be interested in
that.
-chris
On 25 sep 2010, at 21:31, Jonathan Geddes wrote:
Cafe,
HaskellDB takes a database schema and produces Haskell data structures
(plus some other query-related stuff for its EDSL query language).
What I'm looking for is the inverse of this functionality. I want to
create tables based on a Haskell data structure with a few simple
rules. These rules include: if a field is not of the form `Maybe a'
then it can't be nullable in the database. If a field is not a
primitive (in the database) then it is actually stored in another
table and a reference id is stored in the table. Tables are produced
recursively, unless they already exist, etc.
The HaskellDB approach is great for interfacing with existing tables,
but in my case I already have data structures and now I would like a
quick way to create tables to persist them.
Does such a thing exist? If not, would you find it useful? I may take
this up as a side project if it does not already exist and others
would find it useful.
Thanks,
--Jonathan
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Re: [Haskell-cafe] searching haskell-cafe ?
if you want to use google, here[1], it suggests using the 'list:' keyword to search in a mailing list archives. eg. http://www.google.co.uk/#hl=enq=fundep+list%3Ahaskell-cafe.haskell.org hope this helps, [1] http://mail.google.com/support/bin/answer.py?hl=enanswer=7190 On 20 September 2010 00:01, bri...@aracnet.com wrote: is there a way to search the haskell-cafe list. I found a potential link on the haskell wiki, but the link is busted. Didn't see anything on the haskell-cafe mailing list page. Thanks, Brian ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe -- Ozgur Akgun ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] ghc in macports
sounds good to me. where can I find the list of packages (or whatever they call them in homebrew, formula?) available? On 12 August 2010 11:49, Benedict Eastaugh ionf...@gmail.com wrote: On 11 August 2010 15:49, Ozgur Akgun ozgurak...@gmail.com wrote: Personally, I'd like to use the macports version, if the ghc version there was resonably recent (having 2 versions, a stable and an edge could be a good idea?) You could use Homebrew instead. That has a fairly up-to-date version of GHC and the Haskell Platform. http://mxcl.github.com/homebrew/ -- Ozgur Akgun ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] ghc in macports
On 12 August 2010 12:52, Hans Aberg haber...@telia.com wrote: On http://wiki.github.com/mxcl/homebrew/installation it says: delete /usr/local/include and/usr/local/lib So its not for those that also installs standard distributions, it seems. I thought this was just a recommendation. -- Ozgur Akgun ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] ghc in macports
Dear Cafe, I wonder who is maintaining the ghc package in macports, and what the current stategy of doing things is? http://www.macports.org/ports.php?by=namesubstr=ghc (ghc 6.10.4) Personally, I'd like to use the macports version, if the ghc version there was resonably recent (having 2 versions, a stable and an edge could be a good idea?) Thanks, Ozgur ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Preview the new haddock look and take a short survey
A few points, * The text in Synopsis part is typically wide. (See http://www.ozonehouse.com/mark/snap-xhtml/heist/Text-Templating-Heist.htmlwith Ocean style) I think it would be more *usable *if it was at the bottom of the page (again with a similar button and open/close toggling effect) * On my browser (firefox on a mac) if I select any of the two styles other than Ocean, module pages seem like they do not apply any style. And also they still reference ocean.css. A cookie problem or something like that? * Opening the synopsis frame (either at its current position or at the bottom of the page) might be better if it was implemented as a preference. Namely, if I open the synopsis frame in a module page, I'd possibly like to see it in the next modules page as well. Carrying that information to the same extend as preferred style information sounds like a better idea to me. Thanks for the work! Best, On 4 August 2010 06:00, Mark Lentczner ma...@glyphic.com wrote: The Haddock team has spent the last few months revamping the look of the generated output. We're pretty close to done, but we'd like to get the community's input before we put it in the main release. Please take a look, and then give us your feedback through a short survey Sample pages: http://www.ozonehouse.com/mark/snap-xhtml/index.html Frame version: http://www.ozonehouse.com/mark/snap-xhtml/frames.html Survey: http://spreadsheets.google.com/viewform?formkey=dHcwYzdMNkl5WER1aVBXdV9HX1l5U3c6MQ Short link to same survey: http://bit.ly/9Zvs9B Thanks! - Mark Mark Lentczner http://www.ozonehouse.com/mark/ irc: MtnViewMark ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe -- Ozgur Akgun ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Suggestions For An Intro To Monads Talk.
Today I read this fantastic blog post: You Could Have Invented Monads! (And Maybe You Already Have.) http://blog.sigfpe.com/2006/08/you-could-have-invented-monads-and.html You most probably have seen the post by now, but I just wanted to remind it, just in case. Best, On 3 August 2010 22:51, aditya siram aditya.si...@gmail.com wrote: Hi all, I am doing an Intro To Monads talk in September [1]. The audience consists of experienced non-Haskell developers but they will be familiar with basic functional concepts (closures, first-class functions etc.). I am looking for suggestions on how to introduce the concept and its implications. I'd also like to include a section on why monads exist and why we don't really see them outside of Haskell. Has anyone here done a talk like this? And if so what parts of your presentation were successful and what would you stay away from. Thanks for the feedback. -deech [1] It's in St.Louis, Missouri at the St.Louis Perl Mongers meetinghttp://St.Louis%20Perl%20Mongers%20meetingso come on by if you're around! ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe -- Ozgur Akgun ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Is 'flip' really necessary?
I think it is pretty cool as well. But I think there is a problem with viewing it as a wildcard. let's say we define the following: (??) = flip foo :: a - b - c foo ?? x :: a - c Perfect! But saying ?? can be used as a wildcard might in the following wrong perception: foo x ?? :: b - c -- WRONG Just a small concern. Other than that, very neat! On 26 July 2010 21:42, Nils m...@n-sch.de wrote: On 26.07.2010 08:33, David Virebayre wrote: listeEtagTot = concatMap (`listeEtagArm` cfgTypesTringle) listeArmOrd You can use flip as a wildcard aswell: listeEtagTot = concatMap (listeEtagArm `flip` cfgTypesTringle) listeArmOrd Makes it even more readable in my opinion, since this really shows you where the value belongs to. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe -- Ozgur Akgun ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Random this! ;-)
Sorry but I'll just go ahead and eta reduce it :)
rollNDiceIO = flip replicateM $ randomRIO (1,6)
On 25 July 2010 16:44, Max Rabkin max.rab...@gmail.com wrote:
On Sun, Jul 25, 2010 at 5:39 PM, michael rice nowg...@yahoo.com wrote:
I know, ugly, but at least I got it to work. What's a better way to
generate this list?
rollNDiceIO n
= sequence . replicate n $ randomRIO (1,6)
{{ sequence . replicate n = replicateM n }}
= replicateM n $ randomRIO (1, 6)
--Max
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Re: [Haskell-cafe] Re: GATD and pattern matching
I don't know whether its a good name or not (the ===), but I have the following in a generic utilities file I have, and I use it every now and then. (===) :: (Typeable a, Typeable b, Eq b) = a - b - Bool (===) x y = cast x == Just y (Notice you don't need Eq a in the context) On 11 June 2010 12:51, Ben Millwood hask...@benmachine.co.uk wrote: On Fri, Jun 11, 2010 at 12:46 AM, Felipe Lessa felipe.le...@gmail.com wrote: eqTypeable :: (Typeable a, Eq a, Typeable b, Eq b) = a - b - Bool eqTypeable x y = case cast y of Just y' - x == y' Nothing - False ...or indeed: eqTypeable x y = cast x == Just y ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe -- Ozgur Akgun ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
