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ghci debugger problem with :continue. is it broken, or is it me?
by Thomas Hartman 28 Apr '09

28 Apr '09

In the program below, can someone explain the following debugger output to me? After :continue, shouldn't I hit the f breakpoint two more times? Why do I only hit the f breakpoint once? Is this a problem in the debugger? thartman@ubuntu:~/haskell-learning/debugger>cat debugger.hs -- try this: -- ghci debugger.hs -- > :break f -- > :trace t -- > :history -- should show you that f was called from h t = h . g . f $ "hey!" t2 = h . g . f $ "heh!" t3 = h . g . f $ "wey!" f = ("f -- " ++) g = ("g -- " ++) h = ("h -- " ++) ts = do putStrLn $ t putStrLn $ t2 putStrLn $ t3 {- Problems using :continue in the ghci debugger? Can someone explain the following debugger output to me? After :continue, shouldn't I hit the f breakpoint two more times? Why do I only hit the f breakpoint once? Is this a problem in the debugger? thartman@ubuntu:~/haskell-learning/debugger>ghci debugger.hs GHCi, version 6.10.1: http://www.haskell.org/ghc/ :? for help Loading package ghc-prim ... linking ... done. Loading package integer ... linking ... done. Loading package base ... linking ... done. [1 of 1] Compiling Main ( debugger.hs, interpreted ) Ok, modules loaded: Main. *Main> :break f Breakpoint 0 activated at debugger.hs:12:4-15 *Main> ts h -- g -- Stopped at debugger.hs:12:4-15 _result :: [Char] -> [Char] = _ 11 12 f = ("f -- " ++) ^^^^^^^^^^^^ 13 g = ("g -- " ++) [debugger.hs:12:4-15] *Main> :continue f -- hey! h -- g -- f -- heh! h -- g -- f -- wey! *Main> -}

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LondonHUG talk: Engineering Large Projects in Haskell
by Don Stewart 28 Apr '09

28 Apr '09

Slides from last week's London HUG http://www.londonhug.net/ talk are now online. The talk attempts to document some of the tips and tricks Galois has accumulated using Haskell commercially for the past 10 years. You can now read the slides of the talk here: http://www.galois.com/blog/2009/04/27/engineering-large-projects-in-haskell… Cheers, Don

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Problem with installing phooey
by Daryoush Mehrtash 28 Apr '09

28 Apr '09

When I try to install Phooey I get the following error: cabal install --constraint="Stream == 0.3" phooey Resolving dependencies... [1 of 1] Compiling Main ( /tmp/phooey-2.016943/phooey-2.0/Setup.lhs, /tmp/phooey-2.016943/phooey-2.0/dist/setup/Main.o ) Linking /tmp/phooey-2.016943/phooey-2.0/dist/setup/setup ... Configuring phooey-2.0... Warning: No 'build-type' specified. If you do not need a custom Setup.hs or ./configure script then use 'build-type: Simple'. Preprocessing library phooey-2.0... Building phooey-2.0... src/Graphics/UI/Phooey/WinEvents.hs:66:7: Could not find module `Data.Reactive': Use -v to see a list of the files searched for. It seems that the current version of reactive (0.10.5) no longer has Data.Reactive module (it seem to have been removed since 0.5 version of the reactive). Does Phooey really need 0.5 version of the reactive or is there a problem in my installation? Thanks Daryoush

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createProcess problem
by Vasili I. Galchin 28 Apr '09

28 Apr '09

Hello, I am trying to use createProcess. Following is a small fragment. I am trying to run a program called blastall (a bio-informatics program). It is kind of like mv/cp/ln on Unix platforms (where the executable examines the program, i.e. arg[0], and then provides appropriate behavior/semantics). In the case of blastall, it alters its behavior based on the -p(program) CLI argument.WSo in the following it should provide nucleotide behavior ... that is what the 'n' on the end of blastn means. import System.Process main = do handle <- runProcess "blastall" -- executable ["-p blastn"] -- CLI args Nothing -- optional cwd Nothing -- optional env Nothing -- optional stdin Nothing -- optional stdout Nothing -- optional stderr return () When I run this program with ghci, blastall is not a happy camper. It is complaining about "-p blastn": [NULL_Caption] ERROR: Program name undefined: " blastn" <<< the space between the double quote and 'b' is really there!!! [NULL_Caption] ERROR: Program name undefined: " blastn" Yet if I run 'blastall -p blastn' from the DOS prompt no errors(I will try tonight on my Linux machine). If I try 'blastall -p bozo" from the DOS prompt I get the same two errors as when I run my test program using ghci. I feel that it has something to do with double quotes in Haskell ... probably something obviously silly that I am doing. Any ideas? Kind regards, Vasili

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createProcess problem
by Vasili I. Galchin 28 Apr '09

28 Apr '09

Hello, I am trying to use createProcess. Following is a small fragment. I am trying to run a program called blastall (a bio-informatics program). It is kind of like mv/cp/ln on Unix platforms (where the executable examines the program, i.e. arg[0], and then provides appropriate behavior/semantics). In the case of blastall, it alters its behavior based on the -p(program) CLI argument.WSo in the following it should provide nucleotide behavior ... that is what the 'n' on the end of blastn means. import System.Process main = do handle <- runProcess "blastall" -- executable ["-p blastn"] -- CLI args Nothing -- optional cwd Nothing -- optional env Nothing -- optional stdin Nothing -- optional stdout Nothing -- optional stderr return () When I run this program with ghci, blastall is not a happy camper. It is complaining about "-p blastn": [NULL_Caption] ERROR: Program name undefined: " blastn" <<< the space between the double quote and 'b' is really there!!! [NULL_Caption] ERROR: Program name undefined: " blastn" Yet if I run 'blastall -p blastn' from the DOS prompt no errors(I will try tonight on my Linux machine). If I try 'blastall -p bozo" from the DOS prompt I get the same two errors as when I run my test program using ghci. I feel that it has something to do with double quotes in Haskell ... probably something obviously silly that I am doing. Any ideas? Kind regards, Vasili

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Announce: GraphViz: Change of Maintainer
by Matthew Sackman 27 Apr '09

27 Apr '09

I no longer have the time to continue development of the (apparently, judging from the number of emails I'm getting, rather popular) graphviz package. Fortunately, Ivan Lazar Miljenovic who has extended it himself and sent me patches (some of which I did get round to folding in) has agreed to take on the package. Please direct all further queries to him! Many thanks Ivan! Matthew

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LAST CALL: Haskell Communities and Activities Report
by voigt＠tcs.inf.tu-dresden.de 27 Apr '09

27 Apr '09

Dear Haskellers, It is not yet too late to contribute to the May 2009 edition of the Haskell Communities and Activities Report. If you haven't already, please write an entry for your new project, or update your old entry. Please mail your entries to hcar(a)haskell.org in LaTeX format. More information can be found in the original Call for Contributions at http://www.haskell.org/pipermail/haskell/2009-April/021180.html I look forward to receiving your contributions. Thanks a lot, Janis. -- Dr. Janis Voigtlaender http://wwwtcs.inf.tu-dresden.de/~voigt/ mailto:voigt@tcs.inf.tu-dresden.de

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how can one load Prelude into ghci?
by Thomas Hartman 27 Apr '09

27 Apr '09

One reason it would be nice to be able to do this, is you could then get lambdabot :src style listings of prelude function definitions by using the ghci debugger and :list for prelude functions. is this possible? so far I have tried thartman@ubuntu:~/haskellInstalls/ghcInstalls/source/ghc-6.10.1/libraries/base>head Prelude.hs {-# OPTIONS_GHC -XNoImplicitPrelude #-} ----------------------------------------------------------------------------- thartman@ubuntu:~/haskellInstalls/ghcInstalls/source/ghc-6.10.1/libraries/base>ghci -i. Prelude.hs GHCi, version 6.10.1: http://www.haskell.org/ghc/ :? for help Loading package ghc-prim ... linking ... done. Loading package integer ... linking ... done. Loading package base ... linking ... done. <command line>: module `Prelude' is not loaded thartman@ubuntu:~/haskellInstalls/ghcInstalls/source/ghc-6.10.1/libraries/base>ghci Prelude.hs GHCi, version 6.10.1: http://www.haskell.org/ghc/ :? for help Loading package ghc-prim ... linking ... done. Loading package integer ... linking ... done. Loading package base ... linking ... done. <command line>: module `Prelude' is not loaded

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Memory usage of cabal install
by Krzysztof Kościuszkiewicz 27 Apr '09

27 Apr '09

Hello Haskell-Café, I have a problem with high memory usage of cabal-install. Whenever I try to install or upgrade a package, cabal manages to consume 1,3G of memory before I killed it (on a 32-bit machine with 1 GB of memory). Increasing verbosity does not help, memory consumption goes up after the message "Resolving dependencies..." shows up. I use ghc 6.8.2 and cabal-install version 0.5.1 using version 1.4.0.1 of the Cabal library. Is there a workaround? I would like to avoid fetching & building packages manually. -- Krzysztof Kościuszkiewicz "Simplicity is the ultimate sophistication" -- Leonardo da Vinci

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"subscribing" to the comments, online Real World Haskell
by Michael P Mossey 27 Apr '09

27 Apr '09

I love that Real World Haskell is online, here: <http://book.realworldhaskell.org/read/> I love that it has a comment section embedded with every paragraph. However, I would like some ability to subscribe to specific comments. I want to see if people have replied to me or what the latest discussion is. Anyone know if this is possible by a method other than manually copying down every URL? (In fact, I'm not sure that I can create a URL that goes directly to a part of a chapter.) Thanks, Mike

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