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Month in Haskell Mode December 2015
by Gracjan Polak 01 Jan '16

01 Jan '16

Welcome Haskell Mode users, Haskell Mode progress report for December 2015. For previous issue see November 2015 <https://github.com/haskell/haskell-mode/wiki/Month-in-Haskell-Mode-November…> . Reddit discussion <https://www.reddit.com/r/haskell/comments/3z063t/month_in_haskell_mode_dece…> . <https://github.com/haskell/haskell-mode/wiki/Month-in-Haskell-Mode-December…>What is Haskell Mode? Haskell Mode is an umbrella project for multiple Emacs tools for efficient Haskell development. Haskell Mode is an open source project developed by a group of volunteers constantly looking for contributions. For more information see https://github.com/haskell/haskell-mode. <https://github.com/haskell/haskell-mode/wiki/Month-in-Haskell-Mode-December…>Important developments Font locking now knows how to use language specific syntax coloring for quasi quotes. {-# LANGUAGE QuasiQuotes #-} query conn [sql| SELECT column_a, column_b FROM table1 NATURAL JOIN table2 WHERE ? <= time AND time < ? AND name LIKE ? ORDER BY size DESC LIMIT 100 |] (beginTime,endTime,string) Indentation learned how to indent multiline strings with continuation escapes, for example: main = putStrLn "Multiline\n\ \Hello\n\ \World!\n" <https://github.com/haskell/haskell-mode/wiki/Month-in-Haskell-Mode-December…>Current project focus Current project focus is to lower entry barrier for newcomers by defining bite-sized tasks. Get 50 'well-defined-tasks' done as by the metric: https://github.com/haskell/haskell-mode/issues?q=is%3Aissue+label%3Awell-de… A 'well-defined-task' is a category of tasks that have the field cleared for them, questions already sorted out and detailed information how to get them done. So you can just sit, search for 'well-defined-task' label and enjoy the coding! The point is to lower the entry barrier for new users, new issue reporters and advanced programmers but Emacs lisp beginners to contribute to the project. Current status: 14 well-defined-tasks closed <https://github.com/haskell/haskell-mode/issues?q=is%3Aissue+label%3Awell-de…> plus 13 more open <https://github.com/haskell/haskell-mode/issues?q=is%3Aissue+label%3Awell-de…> . If only you can help with reaching our targets please do so! <https://github.com/haskell/haskell-mode/wiki/Month-in-Haskell-Mode-December…>Issues closed in December - Flymake produce temp file without cleaning it up #130 <https://github.com/haskell/haskell-mode/issues/130> - haskell-indentation's behaviour is slightly different from haskell-indent #208 <https://github.com/haskell/haskell-mode/issues/208> - Support shallow indentation #366 <https://github.com/haskell/haskell-mode/issues/366> - flymake-init uses nil haskell-saved-check-command #384 <https://github.com/haskell/haskell-mode/issues/384> - haskell-mode prompts for a new session every emacs session #407 <https://github.com/haskell/haskell-mode/issues/407> - On opening a file, haskell-doc opens several files defined in import section #742 <https://github.com/haskell/haskell-mode/issues/742> - haskell-indentation-indent-region and smartparens interact poorly #796 <https://github.com/haskell/haskell-mode/issues/796> - Is it possible to use ghci-ng with "stack-ghci" haskell-process-type? #889 <https://github.com/haskell/haskell-mode/issues/889> - Use caching docker TravisCI infrastructure #910 <https://github.com/haskell/haskell-mode/issues/910> - Makefile doesn't work in a shell under emacs #972 <https://github.com/haskell/haskell-mode/issues/972> - Emacs hangs when typing behind whitespace #980 <https://github.com/haskell/haskell-mode/issues/980> - Make haskell-indentation-phrase-rest non-recursive #998 <https://github.com/haskell/haskell-mode/issues/998> - Case indentation error #1000 <https://github.com/haskell/haskell-mode/issues/1000> - Stray ^H characters appear in haskell-process-log #1009 <https://github.com/haskell/haskell-mode/issues/1009> - Broken indentation in Emacs 24.5 #1013 <https://github.com/haskell/haskell-mode/issues/1013> - Haskell indentation weirdly re-indents lines after sp-kill-sexp #1031 <https://github.com/haskell/haskell-mode/issues/1031> <https://github.com/haskell/haskell-mode/wiki/Month-in-Haskell-Mode-December…>Pull requests merged in December - Remove horizontal whitespace based smart indentation mode haskell-simple-indent #958 <https://github.com/haskell/haskell-mode/pull/958> - Remove haskell-bot.el #960 <https://github.com/haskell/haskell-mode/pull/960> - Bump version to 13.17-git #1007 <https://github.com/haskell/haskell-mode/pull/1007> - Guard stack overflow, introduce a test #1008 <https://github.com/haskell/haskell-mode/pull/1008> - Failing testcase for bug #981: M-j to continue a comment on the next lines indents the next line #1010 <https://github.com/haskell/haskell-mode/pull/1010> - Non-recursive haskell-indentation-phrase-rest #1011 <https://github.com/haskell/haskell-mode/pull/1011> - Add test for a case expression with multiple paths on their own lines. #1016 <https://github.com/haskell/haskell-mode/pull/1016> - Check indentation per line #1017 <https://github.com/haskell/haskell-mode/pull/1017> - Show expected result first in haskell indentation tests #1018 <https://github.com/haskell/haskell-mode/pull/1018> - Support shallow indentation #1019 <https://github.com/haskell/haskell-mode/pull/1019> - Use vanilla buffer file name for hlint command #1020 <https://github.com/haskell/haskell-mode/pull/1020> - Use Trusty platform for TravisCI #1021 <https://github.com/haskell/haskell-mode/pull/1021> - Find Emacs once #1023 <https://github.com/haskell/haskell-mode/pull/1023> - Case expression indentation fix #1024 <https://github.com/haskell/haskell-mode/pull/1024> - Simpler apt-get #1025 <https://github.com/haskell/haskell-mode/pull/1025> - Fix align imports for modules named "Instance" #1028 <https://github.com/haskell/haskell-mode/pull/1028> - Add some common extensions to haskell-rgrep #1029 <https://github.com/haskell/haskell-mode/pull/1029> - Remove haskell-indentation-dyn-first-position #1030 <https://github.com/haskell/haskell-mode/pull/1030> - Cleanup tests with with-temp-switch-to-buffer #1033 <https://github.com/haskell/haskell-mode/pull/1033> - Indent multiline strings #1035 <https://github.com/haskell/haskell-mode/pull/1035> - Implement font-lock for quasi quoted XML, HTML and JavaScript #1036 <https://github.com/haskell/haskell-mode/pull/1036> <https://github.com/haskell/haskell-mode/wiki/Month-in-Haskell-Mode-December…>Contributors active in December Emmanuel Touzery, Gracjan Polak, Sergey Vinokurov, Wayne Lewis, vwyu <https://github.com/haskell/haskell-mode/wiki/Month-in-Haskell-Mode-December…> Contributing Haskell Mode needs volunteers like any other open source project. For more information see: https://github.com/haskell/haskell-mode/wiki Also drop by our IRC channel: #haskell-emacs at irc.freenode.net. Thanks!

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Question on nested fmaps.
by David Banas 31 Dec '15

31 Dec '15

Is this true, in general?: fmap h (fmap g f) == fmap (h . g) f Is there a simple proof? Thanks, -db

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Naming inner elements
by amindfv＠gmail.com 31 Dec '15

31 Dec '15

I've looked all around but haven't found a nice syntax for this -- anyone have suggestions?: What I'd like to do is assign toplevel variable names to inner elements of a structure. Pseudocode for what I'd like to do is: things = [ foo@"thing1" , bar@"thing2" ] The major difference from just `foo = "thing1" ; things = [foo, ...` is that it's much more visually clear which values are in `things` (imagine I create a `baz` but forget to add it to `things`). The best I've found (which is not at all ideal) is to say e.g.: things@ [ foo , bar , baz ] = ["thing1", "thing2", "thing3"] But of course, for starters, I run off the page very quickly. I don't see anything in the usual places (e.g. the Haskell Report), but has anyone come across this and found an elegant solution? Thanks! Tom

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costate
by Peter Padawitz 31 Dec '15

31 Dec '15

When is cobinding in the costate/funarg/incontext comonad (c -> a,c) (see papers by Kieburtz, Uustalu, Vene, Orchard, Mycroft, …) preferable to (better-known) currying? f <<= (g,x) is equivalent to (curry f g,x) ! HNY, Peter

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Make this code more idiomatic?
by David Turner 30 Dec '15

30 Dec '15

Hi, I'd like to use the Control.Parallel.Strategies machinery to evaluate parts of a big record-based data structure in the background. The following code is the sort of thing that I've ended up with - it makes a spark that forces the actuals field of a user object, in the sense that it forces all of the elements to WHNF. (At least, that's what I hope it's doing!) updateActuals user = runEval $ do newActuals <- rparWith (evalTraversable rseq) $ calculateActuals user return user { actuals = newActuals } However, I'm concerned that runEval is marked as "for Strategy programmers" and that I should be using some collection of combinators instead of dropping down to this level. But I just can't work out how to combine the available combinators to do the same thing. In particular, all the articles I've found about this seem to end up adding `using` something to the end of one key line of code to achieve near-perfect parallelisation, but now that I come to do it myself I'm stuck! I think I'm looking for something like: updateActuals user = user { actuals = newActuals } `using` ... Can anyone help me fill in the blank there? Many thanks, David

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ANN: wxInstall Achelanne and wxHaskell 0.92.2.0
by Henk-Jan van Tuyl 30 Dec '15

30 Dec '15

L.S., I am happy to announce a new version of wxHaskell: 0.92.2.0 and new installation packages for wxHaskell on Windows: wxInstall Achelanne 0.1 (32 bit and 64 bit) Changes in wxHaskell since 0.92.1: - Solved warnings for wxcore, wxdirect, wxc - Added support for Pickerctrl, Hyperlinkctrl and some Streams in wxc and wxcore - Solved several bugs - Added some image Functions in wxc and wxcore - Added enumerateFonts function in wxcore - Updated wxBITMAP_TYPE_ constants - Adapted to GHC 7.10.3 Thanks to everyone who contributed! wxInstall Achelanne[0] is created because GHC 7.10.3 for Windows is accompanied with a newer GCC: 5.2.0. A detailed description can be found at the wxHaskell-for-Windows homepage[1]. What is wxHaskell? ------------------ wxHaskell[2] is a portable and native GUI library for Haskell. The goal of the project is to provide an industrial strength GUI library for Haskell, but without the burden of developing (and maintaining) one ourselves. wxHaskell is therefore built on top of wxWidgets – a comprehensive C++ library that is portable across all major GUI platforms; including GTK, Windows, X11, and MacOS X. Furthermore, it is a mature library (in development since 1992) that supports a wide range of widgets with the native look-and-feel. Links ----- See the homepage of wxHaskell for more information: https://wiki.haskell.org/WxHaskell The packages are: - wxc https://hackage.haskell.org/package/wxc - wxdirect https://hackage.haskell.org/package/wxdirect - wxcore https://hackage.haskell.org/package/wxcore - wx https://hackage.haskell.org/package/wx Regards, Henk-Jan van Tuyl [0] http://sourceforge.net/projects/wxhaskell/files/wxInstall/ [1] https://wiki.haskell.org/WxHaskell/Windows#Installing_the_easy_way [2] https://wiki.haskell.org/WxHaskell -- Folding@home What if you could share your unused computer power to help find a cure? In just 5 minutes you can join the world's biggest networked computer and get us closer sooner. Watch the video. http://folding.stanford.edu/ http://Van.Tuyl.eu/ http://members.chello.nl/hjgtuyl/tourdemonad.html Haskell programming --

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I need repositories that contain commited erroneous code
by Rick Klomp 30 Dec '15

30 Dec '15

Hi Haskell community, For my master thesis project I need change logs that I can use to derive what changes have been made to fix certain compilation errors. Unfortunately so for me, good repository etiquette is to never commit erroneous code. However, there are bound to be plenty of repos where this etiquette isn't/hasn't been followed (in non-main branches). My question to you is if you currently know or at some point in the near future (new data will be useful until somewhere early summer 2016) come to know of repos that fit the description, could you point me to them? Much appreciated! Or if you are willing to share a personal project with me (where obviously this repo etiquette is much less significant), then that would be immensely helpful to me! I promise to only use the metadata (but you'll have to believe me on my word). Thanks in advance for your help. Best regards, Rick Klomp

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Re: [Haskell-cafe] Preventing sharing
by Oleg 28 Dec '15

28 Dec '15

> -fno-full-laziness fixes the space leak issue in your iterative deepening > example. Yes, and I think it has been mentioned that the flag is a blunt weapon as it affects the whole module... > This isn't a problem with laziness. It's a problem with performing a time > optimization which is a space pessimization. In the absence of the > "optimization" there is no problem. How come it isn't the problem with laziness?! Recall, that pure call-by-name calculus is observationally undistinguishable from the call-by-need (i.e., lazy) calculus. The only reason to have laziness is to avoid recomputations of argument computations should an argument be used more than once -- at the cost of taking memory to store the result of the first evaluation. Thus "performing a time optimization which is a space pessimization" is exactly what laziness is all about -- as the article mentioned earlier argued. Laziness isn't an absolute good -- it is a time-space trade-off, which is not always beneficial.

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[ANN] Flashy-Haskell: Advanced Haskell syntax for Vim
by mwnx 26 Dec '15

26 Dec '15

In case anyone is interested, I just published a syntax extension I use for vim. It adds on to the default "haskell.vim" syntax file and enables some more advanced colouring. Here's the link to the github page, with visual examples: https://github.com/mwnx/flashy-haskell I rewrote the whole thing before publishing so there might be quite a few bugs due to a lack of real world testing, but I'll strive to fix any reported bugs rapidly. It also doesn't seek to completely and perfectly interpret Haskell's syntax. As a result, some of the more unusual syntactic constructs might not benefit from the extra colouring. -- mwnx GPG: AEC9 554B 07BD F60D 75A3 AF6A 44E8 E4D4 0312 C726

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Q: language-c upstream repo
by Ivan Zakharyaschev 25 Dec '15

25 Dec '15

Hello! I've been interested in hacking language-c library a bit for my needs. (If it turns out useful and successful, I'll tell about it.) And I've cloned the repo listed at https://hackage.haskell.org/package/language-c-0.4.7 , namely: http://code.haskell.org/language-c Apart from my special hacks, I've also fixed some typos and so on. But then I discovered that if I want to publish them on hub.darcs.net , I need a darcs-2 repo, and the initial one which I used for cloning is a darcs-1 repo. I could do the conversion to darcs-2, but I read that it is not reproducible: run several times on the same set of patches it will give different results. As I've discovered also a language-c repo at hub.darcs.net which looks like an upstream repo: http://hub.darcs.net/visq/language-c , I'm in doubt whether I should continue making my patches against the darcs-1 repo which is said to be upstream at hackage or against http://hub.darcs.net/visq/language-c whichis not officially declared as the upstream but looks more fresh. ..if I want to be able to send some of my patches upstream. Best regards, Ivan

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ANN: stack-1.0.0
by Emanuel Borsboom 25 Dec '15

25 Dec '15

A Christmas present: we’re calling this version 1.0! This is a minor enhancement and bug fix release, but since Stackage LTS 4 is about to be cut we thought it was time to give Stack a version number that reflects its readiness for production use. Enhancements: - Added flag --profile flag: passed with stack build, it will enable profiling, and for --bench and --test it will generate a profiling report by passing +RTS -p to the executable(s). Great for using like stack build --bench --profile (remember that enabling profile will slow down your benchmarks by >4x). Run stack build --bench again to disable the profiling and get proper speeds - Added flag --trace flag: just like --profile, it enables profiling, but instead of generating a report for --bench and --test, prints out a stack trace on exception. Great for using like stack build --test --trace - Nix: all options can be overriden on command line #1483 <https://github.com/commercialhaskell/stack/issues/1483> - Nix: build environments (shells) are now pure by default. - Make verbosity silent by default in script interpreter mode #1472 <https://github.com/commercialhaskell/stack/issues/1472> - Show a message when resetting git commit fails #1453 <https://github.com/commercialhaskell/stack/issues/1453> - Improve Unicode handling in project/package names #1337 <https://github.com/commercialhaskell/stack/issues/1337> - Fix ambiguity between a stack command and a filename to execute (prefer stack subcommands) #1471 <https://github.com/commercialhaskell/stack/issues/1471> - Support multi line interpreter directive comments #1394 <https://github.com/commercialhaskell/stack/issues/1394> - Handle space separated pids in ghc-pkg dump (for GHC HEAD) #1509 <https://github.com/commercialhaskell/stack/issues/1509> - Add ghci —no-package-hiding option #1517 <https://github.com/commercialhaskell/stack/issues/1517> - stack new can download templates from URL #1466 <https://github.com/commercialhaskell/stack/issues/1466> Bug fixes: - Nix: stack exec options are passed properly to the stack sub process #1538 <https://github.com/commercialhaskell/stack/issues/1538> - Nix: specifying a shell-file works in any current working directory #1547 <https://github.com/commercialhaskell/stack/issues/1547> - Nix: use --resolver argument - Docker: fix missing image message and ‘—docker-auto-pull’ - No HTML escaping for “stack new” template params #1475 <https://github.com/commercialhaskell/stack/issues/1475> - Set permissions for generated .ghci script #1480 <https://github.com/commercialhaskell/stack/issues/1480> - Restrict commands allowed in interpreter mode #1504 <https://github.com/commercialhaskell/stack/issues/1504> - stack ghci doesn’t see preprocessed files for executables #1347 <https://github.com/commercialhaskell/stack/issues/1347> - All test suites run even when only one is requested #1550 <https://github.com/commercialhaskell/stack/pull/1550> - Edge cases in broken templates give odd errors #1535 <https://github.com/commercialhaskell/stack/issues/1535> - Fix test coverage bug on windows

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Re: [Haskell-cafe] Formatting strict Text
by Mark Fine 24 Dec '15

24 Dec '15

I've been using Formatting <http://hackage.haskell.org/package/formatting> recently. Mark On Wed, Dec 23, 2015 at 5:13 PM, fr33domlover <fr33domlover(a)riseup.net> wrote: > Hello, > > I have code which uses Text.Printf.printf with String. Now I'm moving the > code > to use strict Text everywhere (I picked strict since all my strings are > very > short, mostly less than 400 chars). What should I use instead of printf > now? > > One solution I found is the text-format package, which seems to simply > split a > Text on occurences of "{}" and insert values there. Are there other simple > and > efficient options? All I need is to append Text values and sometimes Ints > too, > so it's enough to have > > (1) efficient append and concat > (2) A function that is :: Int -> Text > > Why is strict Text not a Monoid instance? And Builder has no `toStrictText` > function? There is a function to convert Int to Builder and a Buildable > instance for Int, but for a simple Int->Text it seems I'm left with an ugly > `T.pack . show`. > > > Suggestions / advice / comments on this? > > Thanks in advance :) > > fr33 > > _______________________________________________ > Haskell-Cafe mailing list > Haskell-Cafe(a)haskell.org > http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe > >

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Installation instructions for ghc 7-10-3 on Windows
by Lian Hung Hon 24 Dec '15

24 Dec '15

Dear Haskellers, How can I install just ghc on Windows? Especially with regards to the network package? Before this I used minghc, but the github page says its now dead. Sincerely, Hon

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Re: [Haskell-cafe] Formatting strict Text
by fr33domlover 24 Dec '15

24 Dec '15

On Thu, 24 Dec 2015 00:13:34 +0200 fr33domlover <fr33domlover(a)riseup.net> wrote: > Hello, > > I have code which uses Text.Printf.printf with String. Now I'm moving the code > to use strict Text everywhere (I picked strict since all my strings are very > short, mostly less than 400 chars). What should I use instead of printf now? > > One solution I found is the text-format package, which seems to simply split a > Text on occurences of "{}" and insert values there. Are there other simple and > efficient options? All I need is to append Text values and sometimes Ints too, > so it's enough to have > > (1) efficient append and concat > (2) A function that is :: Int -> Text > > Why is strict Text not a Monoid instance? And Builder has no `toStrictText` > function? There is a function to convert Int to Builder and a Buildable > instance for Int, but for a simple Int->Text it seems I'm left with an ugly > `T.pack . show`. > > > Suggestions / advice / comments on this? > > Thanks in advance :) > > fr33 Since Text does have a Monoid instance after all, another question: The docs say 'append' is subject to fusion, but it isn't said about 'concat'. When I need to append several texts together, does it matter whether I just use <> between then or I 'concat' a list of them? Any one of them recommended / more efficient? I don't have any performance issues in my program, I just want to create good habits now and not get used to bad ones :P --fr33

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Re: [Haskell-cafe] Formatting strict Text
by Adam Bergmark 24 Dec '15

24 Dec '15

Data.Text definitely has a Monoid instance, it's defined in Data.Text. - Adam On Wed, Dec 23, 2015 at 11:13 PM, fr33domlover <fr33domlover(a)riseup.net> wrote: > Hello, > > I have code which uses Text.Printf.printf with String. Now I'm moving the > code > to use strict Text everywhere (I picked strict since all my strings are > very > short, mostly less than 400 chars). What should I use instead of printf > now? > > One solution I found is the text-format package, which seems to simply > split a > Text on occurences of "{}" and insert values there. Are there other simple > and > efficient options? All I need is to append Text values and sometimes Ints > too, > so it's enough to have > > (1) efficient append and concat > (2) A function that is :: Int -> Text > > Why is strict Text not a Monoid instance? And Builder has no `toStrictText` > function? There is a function to convert Int to Builder and a Buildable > instance for Int, but for a simple Int->Text it seems I'm left with an ugly > `T.pack . show`. > > > Suggestions / advice / comments on this? > > Thanks in advance :) > > fr33 > > _______________________________________________ > Haskell-Cafe mailing list > Haskell-Cafe(a)haskell.org > http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe > >

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Formatting strict Text
by fr33domlover 23 Dec '15

23 Dec '15

Hello, I have code which uses Text.Printf.printf with String. Now I'm moving the code to use strict Text everywhere (I picked strict since all my strings are very short, mostly less than 400 chars). What should I use instead of printf now? One solution I found is the text-format package, which seems to simply split a Text on occurences of "{}" and insert values there. Are there other simple and efficient options? All I need is to append Text values and sometimes Ints too, so it's enough to have (1) efficient append and concat (2) A function that is :: Int -> Text Why is strict Text not a Monoid instance? And Builder has no `toStrictText` function? There is a function to convert Int to Builder and a Buildable instance for Int, but for a simple Int->Text it seems I'm left with an ugly `T.pack . show`. Suggestions / advice / comments on this? Thanks in advance :) fr33

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wiki account creation
by Artúr Poór 23 Dec '15

23 Dec '15

Hello, I would like to create a new wiki account. The automatic account creation has been disabled, and requests should be sent to domain(a)haskell.org. However, my email has been returned as undelivered. Could someone help with the account creation? Artúr

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NoMonomorphismRestriction forces odd situation when using contexts
by Noon Silk 23 Dec '15

23 Dec '15

Hello, Consider the following program: ------------------------------------------------------------------- -- bar.hs {-# LANGUAGE NoMonomorphismRestriction #-} data Status = Foo | Bar data Rec m a = Rec { get :: m a , status :: Status } defRec :: (Monad m) => Rec m a defRec = undefined myRec :: (Monad m) => Rec m a myRec = Rec x y where Rec x y = defRec ------------------------------------------------------------------- It doesn't compile (under GHC 7.10.2), the error is: bar.hs:16:7: No instance for (Monad t0) The type variable ‘t0’ is ambiguous When checking that ‘y’ has the inferred type y :: Status Probable cause: the inferred type is ambiguous In an equation for ‘myRec’: myRec = Rec x y where Rec x y = defRec Failed, modules loaded: none. If you remove the language extension, it does. Keeping the NoMonomorphismRestriction, it can be forced to typecheck by putting in a "dummy" type that satifies the constraint when obtaining the field `status` (that doesn't depend on `m`. ------------------------------------------------------------------- -- bar.hs {-# LANGUAGE NoMonomorphismRestriction #-} data Status = Foo | Bar data Rec m a = Rec { get :: m a , status :: Status } defRec :: (Monad m) => Rec m a defRec = undefined myRec :: (Monad m) => Rec m a myRec = Rec x y where s :: Rec Maybe a -> Status s = status x = get defRec -- y = s defRec ------------------------------------------------------------------- So, what's going on here? Is this a feature of this extension? It seems like the ability to destructure and then recombine is pretty fundamental, and it shouldn't break in the way that it does. (I.e. it's kinda crazy to have to put in a dummy type satisfying the constraint; is there some way to pass down the error -- Noon Silk, ن https://silky.github.io/ "Every morning when I wake up, I experience an exquisite joy — the joy of being this signature."

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Lazy evaluation illustrated for Haskell divers
by Takenobu Tani 22 Dec '15

22 Dec '15

Dear cafe, I'm studying and enjoying for Haskell. I'm drawing some illustrations about lazy evaluation in Haskell. Of course, I know a lot of pretty good documents. My document is one of the starter-kits to them. Here is: Lazy evaluation illustrated for Haskellers http://takenobu-hs.github.io/downloads/haskell_lazy_evaluation.pdf https://github.com/takenobu-hs/lazy_evaluation If there are misunderstandings, please teach me. I'll correct them. I apology if my responses is late. This is my night work (fun) =) I wish you a happy new year. Enjoy, lazy!, Takenobu

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Data.Map docs missing on hackage
by Andrew Butterfield 22 Dec '15

22 Dec '15

Is there a problem on hackage ?- when I try to look up Data.Map (via Hoogle) I get an error: ------------------- Not Found There is no documentation for containers-0.5.7.1. See https://hackage.haskell.org/package/containers/docs/Data-Map.html for the latest version. ---------------- Going to that link gives the exact same error Andrew Butterfield School of Computer Science & Statistics Trinity College Dublin 2, Ireland

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Re: [Haskell-cafe] Q: language-c upstream repo (fwd)
by Ivan Zakharyaschev 22 Dec '15

22 Dec '15

---------- Forwarded message ---------- Date: Tue, 22 Dec 2015 05:59:17 +0000 From: Benedikt Huber <benedikt.huber(a)gmail.com> To: Ivan Zakharyaschev <imz(a)altlinux.org>, haskell-cafe(a)haskell.org Subject: Re: Q: language-c upstream repo Hi Ivan, the hub.darcs.net repository is a mirror of http://code.haskell.org/language-c (the official upstream) that was created to simplify contributing. Conversion to darcs-2 was not straightforward IIRC, and the update of the repository did not work out.That's why code.haskell.org is still darcs-1. Best, Benedikt Ivan Zakharyaschev <imz(a)altlinux.org> schrieb am So., 20. Dez. 2015 um 16:32 Uhr: Hello! I've been interested in hacking language-c library a bit for my needs. (If it turns out useful and successful, I'll tell about it.) And I've cloned the repo listed at https://hackage.haskell.org/package/language-c-0.4.7 , namely: http://code.haskell.org/language-c Apart from my special hacks, I've also fixed some typos and so on. But then I discovered that if I want to publish them on hub.darcs.net , I need a darcs-2 repo, and the initial one which I used for cloning is a darcs-1 repo. I could do the conversion to darcs-2, but I read that it is not reproducible: run several times on the same set of patches it will give different results. As I've discovered also a language-c repo at hub.darcs.net which looks like an upstream repo: http://hub.darcs.net/visq/language-c , I'm in doubt whether I should continue making my patches against the darcs-1 repo which is said to be upstream at hackage or against http://hub.darcs.net/visq/language-c whichis not officially declared as the upstream but looks more fresh. ..if I want to be able to send some of my patches upstream. Best regards, Ivan

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[ANNOUNCE] sbvPlugin: Run SMT solvers over Haskell "theorems"
by Levent Erkok 22 Dec '15

22 Dec '15

Hello all, I'm happy to announce the first public release of sbvPlugin, a new GHC-core plugin based on the SBV library: http://hackage.haskell.org/package/sbvPlugin The plugin can be used to prove (or refute!) theorems in your Haskell code, using the SBV library as its backend. Here's a most simple example: {-# OPTIONS_GHC -fplugin=Data.SBV.Plugin #-} module Test where import Data.SBV.Plugin {-# ANN test theorem #-} test :: Integer -> Integer -> Bool test x y = x + y >= x - y When compiled (or loaded into ghci), you'll see that the plugin will attempt to prove the given theorem, and will produce a counter-example since it is not valid! (This assumes, you've installed an SBV-supported SMT solver. Z3 from Microsoft is a good choice: http://github.com/Z3Prover/z3) <http://github.com/Z3Prover/z3> The plugin is still in its early days and the examples are rather sparse. But see the following for one worked out instance: (Thanks to Anthony Cowley for the original idea.) http://hackage.haskell.org/package/sbvPlugin/docs/Data-SBV-Plugin-Examples-… The sbvPlugin takes advantage of the SBV library ( http://hackage.haskell.org/package/sbv) to directly reason about Haskell programs at GHC's core level. However, the plugin is *not* a replacement for SBV. It only exposes a few features of SBV directly at the Haskell level; which hopefully makes it useful and more friendly than SBV; but it is neither intended nor possible for it to replace the SBV library itself. In particular, the plugin is limited to certain types (mostly numeric), and a few composite ones (lists and tuples.) If the plugin does not "understand" a Haskell type/expression, it'll use a technique called "uninterpretation" to black-box it. In those cases, the counter-examples produced might be bogus, though proofs will still be valid. Note that any definitions that are outside of the module being compiled will also go uninterpreted, including all the Prelude functions. The plugin is still in its early days, and there are a number of rough edges. Any feedback is most welcome! Happy hacking, -Levent.

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Re: [Haskell-cafe] More disciplined alternative to rewrite rules?
by Johannes Waldmann 21 Dec '15

21 Dec '15

What graph(s) do you want to rewrite? How would this help with respect to A, B, and C? The program is a term (tree), the runtime data structure (heap) is a graph - you want rewriting at run-time then? But the purpose is to move work from run-time to compile-time. - J.W.

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RFC: explicit support for GADTs in Template Haskell
by Jan Stolarek 21 Dec '15

21 Dec '15

GHC Users, I am working on adding proper support for GADTs in Template Haskell. By proper I mean that GADTs data constructors will no longer be encoded using H98 data constructors, but will be represented explicity. GADTs allow to declare several constructors with the same signature: data T where MkT1, MkT2 :: T The question is whether to represent such constructors in TH syntax as: (1) GadtC [Name] [StrictType] Name [Type] -- or: (2) GadtC Name [StrictType] Name [Type] Note the difference in first field. (1) is closer to the original syntax, as it stores the list of all names in a single declaration, as was originally written in the source code. (2) requires to have a separate `GadtC` for each constructor even if constructors were declared together, as in the example above. I would like to hear from TH users which of these two representations you prefer. At the moment I have implemented (1) as it directly represents source syntax. The downside of (1) is that information whether several data constructors were declared together is not recoverable during reification, and so reifying T will yield: data T where MkT1 :: T MkT2 :: T Janek --- Politechnika Łódzka Lodz University of Technology Treść tej wiadomości zawiera informacje przeznaczone tylko dla adresata. Jeżeli nie jesteście Państwo jej adresatem, bądź otrzymaliście ją przez pomyłkę prosimy o powiadomienie o tym nadawcy oraz trwałe jej usunięcie. This email contains information intended solely for the use of the individual to whom it is addressed. If you are not the intended recipient or if you have received this message in error, please notify the sender and delete it from your system.

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wondering on Haskell kickstarter project: VST plugin / mobile synthesizer
by Anton Kholomiov 21 Dec '15

21 Dec '15

I'm wondering if it's good idea to make crowd-founding project for a synthesizer written in Haskell. What's your opinion? Would you like to support such a project? I've made a prototype: https://github.com/anton-k/tiny-synth It's a desktop synthesizer, a collection of instruments. About 150 instruments written in Haskell. It works with midi keyboard. You can try it out with USB-midi device. The UI is written with Python and audio engine is written with Haskell. I use my library csound-expression to generate the code for Csound. The Csound is an audio programming language it can be used as C library. There are bindings to many languages and it can work on Android / iOS. Right now I've made a prototype for desktop. The big plan is to create VST/AU/Lv2 plugins and mobile versions for Android and iOS. [1] https://github.com/anton-k/tiny-synth [2] http://hackage.haskell.org/package/csound-expression [3] https://github.com/spell-music/csound-expression Cheers, Anton

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More disciplined alternative to rewrite rules?
by Will Yager 21 Dec '15

21 Dec '15

Has there been any discussion of replacing rewrite rules with a more disciplined and robust system? Some problems I've noticed with rewrite rules are: A) It's highly syntactic. It isn't really capable of encapsulating intent; it just does restrictively simple term manipulation. B) As a result, many performance-oriented modules seem to have an ungainly number of rewrite rules so as to cover every likely case. C) There are many cases where rewrite rules fail to work as intended, either because the module author missed a rewrite case or because the rewrite fails to fire for some reason. Perhaps a good approach would be to implement a rewrite system in a domain more amenable to simplification rules. For example, there has been a great deal of (quite successful) work on circuit simplification in the form of operations on graphs. Haskell is quite amenable to graph representations, so this approach might work for Haskell as well. -Will

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Imported rewrite rules are ignored
by Johannes Waldmann 21 Dec '15

21 Dec '15

Forgot to say: I confirm your observation for ghc-7.* and I checked that the imported rule *does* fire with ghc-6.10.4.

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Imported rewrite rules are ignored
by Johannes Waldmann 21 Dec '15

21 Dec '15

Well, ghc --show-iface RuleModule.hi does show the rule: rewrite_me :: () -> () {- Strictness: b, Inline: NOINLINE -} "rewrite_me" [ALWAYS] forall input :: () rewrite_me input = ()

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New Functional Programming Job Opportunities
by Functional Jobs 21 Dec '15

21 Dec '15

Here are some functional programming job opportunities that were posted recently: Software Engineer (Scala/Play/Scala.js/React) at AdAgility https://functionaljobs.com/jobs/8871-software-engineer-scala-play-scalajs-r… Cheers, Sean Murphy FunctionalJobs.com

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Imported rewrite rules are ignored
by Alexander Vieth 21 Dec '15

21 Dec '15

Hi café, I observe that rewrite rules from imported modules are ignored by GHC. Given these two files, one module and one executable, the problem can be demonstrated by switching between `rewrite_me` and `rewrite_me_local`. If the rule fires, the program should run cleanly, as the `error` term should be rewritten to `()`. The imported function rewrite_me is not rewritten; but the same thing, rewrite_me_local, defined in the same program, will be rewritten. File RuleModule.hs module RuleModule where {-# NOINLINE rewrite_me #-} rewrite_me :: () -> () rewrite_me = error "Should rewrite" {-# RULES "rewrite_me" forall input . rewrite_me input = () #-} File Rule.hs import RuleModule {-# NOINLINE rewrite_me_local #-} rewrite_me_local :: () -> () rewrite_me_local = error "Should rewrite" {-# RULES "rewrite_local" forall input . rewrite_me_local input = () #-} -- Replace with rewrite_me_local and it's all good. main = case rewrite_me () of () -> return () This is GHC 7.10.2. I compile using -O -fenable-rewrite-rules. Using -dverbose-core2core, the "Desugar (after optimization)" section shows no rules when using rewrite_me, but shows the rule rewrite_local when using the local variant. Maybe this is expected, but I thought it important to mention. Thanks for any advice, Alex

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Preventing sharing
by Oleg 21 Dec '15

21 Dec '15

The old article Preventing memoization in (AI) search problems http://okmij.org/ftp/Haskell/index.html#memo-off deals with the problem, explaining the trick to deliberately confuse GHC so that it won't perform memoization (sharing). Yes, I know how bad this confusing of GHC sounds: which is part of my argument that lazy evaluation by default was a mistake.

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Clausula where
by vieira.ufpi＠gmail.com 20 Dec '15

20 Dec '15

I’m using GHCi in a Haskell version 7.10.2 and using this fragmente of coding: data ArvBinA t = Folha t | No Int (ArvBinA t) (ArvBinA t) deriving (Eq, Ord, Show) arvbina = No 4 (No 2 (Folha 14) (Folha 09)) (No 2 (Folha 19) (Folha 51)) tamArvBinA :: ArvBinA t -> Int tamArvBinA (Folha x) = 1 tamArvBinA (No n xt yt) = n rotula :: ArvBinA t -> ArvBinA t -> ArvBinA t rotula ae ad = No n ae ad where n = (tamArvBinA ae) + (tamArvBinA ad) listoArvBinA :: (Eq t) => [t] -> ArvBinA t listoArvBinA xs |m == 0 = Folha (head xs) |otherwise = rotula (listoArvBinA xse) (listoArvBinA xsd) where m = (length xs) `div` 2 (xse, xsd) = (take m xs, drop m xs) After compiling there is this message: parse error on input ‘=’. There is someone that he/she can help me? I think that’is na error by clause where and the offside rule, or so, but I’m not right of this. Thanks in advance for some help Francisco Vieira Enviado do Email do Windows

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Re: [Haskell-cafe] No instance of ... error with Statistics.Sample.Histogram
by Sigrid Keydana 20 Dec '15

20 Dec '15

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Storable types with zero size
by Douglas McClean 19 Dec '15

19 Dec '15

Can the sizeOf a Storable type be 0? As far as I can see the documentation doesn't say. I wouldn't expect there to be a problem, but there also isn't an instance Storable (), which I was expecting to see. If so, should its alignment be 1 or 0? -Doug McClean

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No instance of ... error with Statistics.Sample.Histogram
by Sigrid Keydana 19 Dec '15

19 Dec '15

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Stackage update and plans for LTS Haskell 4
by Adam Bergmark 19 Dec '15

19 Dec '15

Hi café, This is an update on Stackage moving to GHC 7.10.3 and towards LTS Haskell 4. I especially encourage maintainers with packages on stackage to read the post since some packages have been disabled in the process. http://andnam.tumblr.com/post/135510474243/stackage-update-and-plans-for-lt… All the best, Adam Discussion on Reddit: https://www.reddit.com/r/haskell/comments/3xh5uq/stackage_update_and_plans_…

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Preventing sharing
by David Turner 19 Dec '15

19 Dec '15

I have been playing around with this definition of fib with a colleague: fib n = fibs !! n where fibs = 0 : 1 : zipWith (+) fibs (tail fibs) My initial expectation was that this should take linear time and constant space, but this proved not to be the case: it leaks (a linear amount of) space. We fixed this by replacing (!!) with a version that is strict in the head of its first argument, effectively forcing the list to be strict as far as is needed. With that fix we could quite happily do { print $ fib 1000000 } and all was well, so I tried to write a Criterion benchmark to show that the time taken was linear in n. And the space leak reappeared! Looking at the core, I think what had happened was that GHC had spotted that the inner definition of fibs didn't depend on n and floated it out to the top level so it could be shared between calls. Normally a good move, but in this case it's a disaster as it's much quicker to recalculate the list as needed than to keep it around for next time, for sufficiently large values of n. Now I'm a bit stuck: how do you prevent this from happening? Obviously here we could just implement fibs differently, but as a more general question, how would you prevent unwanted sharing from taking place? Cheers, David

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documentation of Haskell's hierarchical libraries
by s nedunuri 18 Dec '15

18 Dec '15

I am wondering where I might be able to get a reasonably complete documentation of Haskell's libraries. I was using the documentation at https://downloads.haskell.org/~ghc/latest/docs/html/libraries/ but I noticed that it was missing hash tables, which are located in Data.HashTable. I am not sure what other modules might be missing from there. Is there some place where everything (up to some release) is documented? thanks PS the documentation bundled with the Haskell Platform (7.10.2-a) is even worse as its missing large sections of what you find at the online documentation

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Re: [Haskell-cafe] Canned routines for the first say thousand digits of pi, e, sqrt 2, etc?
by Olaf Klinke 18 Dec '15

18 Dec '15

As it happens, I am just studying a presentation [1] Martin Escardo gave to students at the University of Birmingham. It contains Haskell code for exact real number computation. Among other things, there is a function that computes a signed digit representation of pi/32. It computes several thousand digits in a few seconds. I did not try it yet, but many irrational numbers are fixed points of simple arithmetical expressions. For example, the golden ratio is the fixed point of \x -> 1+1/x. Infinite streams of digits should be a type where such a fixed point is computable. Or you could use a sufficiently precise rational approximation and convert that do decimal in the usual way. import Data.Ratio import Data.List (iterate) -- one step of Heron's algorithm for sqrt(a) heron :: (Fractional a) => a -> a -> a heron a x = (x+a/x)/2 -- infinite stream of approximations to sqrt(a) approx :: (Fractional a) => a -> [a] approx a = iterate (heron a) 1 -- Find an interval with rational end-points -- for a signed-digit real number type SDReal = [Int] -- use digits [-1,0,1] interval :: Int -> SDReal -> (Rational,Rational) interval precision x = let f = foldr (\d g -> (a d).g) id (take precision x)) a d = \x -> ((fromIntegral d)+x)/2 in (f(-1),f(1)) Cheers, Olaf [1] www.cs.bham.ac.uk/~mhe/.talks/phdopen2013/realreals.lhs

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Canned routines for the first say thousand digits of pi, e, sqrt 2, etc?
by Jeffrey Brown 18 Dec '15

18 Dec '15

Do there exist libraries for finding the first thousand or so digits of irrational numbers? In base 12? I searhed all the "Numeric" and "Numerical" packages on Hackage and found nothing appropriate. I did figure out how to change the base of a number: https://github.com/JeffreyBenjaminBrown/play/blob/master/digits/chBase.hs but that method appears limited to numbers only a dozen or so digits long. My motivation is this video, in which James Zamerski puts the first couple hundred digits of pi to music. I've listened to it maybe 15 times in two days. https://www.youtube.com/watch?v=AOaR4NS7ObI It makes me want to try playing the first few hundred digits of other irrational numbers on the piano and try to harmonize them. -- Jeffrey Benjamin Brown

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haskell GIS projects
by Noon Silk 18 Dec '15

18 Dec '15

Hello Cafe, Is anyone using any nice modern GIS libraries in Haskell? Say for opening various geographic file formats, and doing geometric queries, etc? Searching often leads me to TerraHS: https://wiki.haskell.org/TerraHS but it's pretty out of date. Is there some cool library I'm missing? -- Noon Silk, ن "Every morning when I wake up, I experience an exquisite joy — the joy of being this signature."

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Need ideas how to model the lack of something
by martin 17 Dec '15

17 Dec '15

Hello all, here is a problem where I did not manage to find a suitable abstraction. The main idea goes like this: a List (and many other containers) can be seen as something containing "stuff". There is a function (:) that unconditionally adds an element to the container and returns a new container Now suppose the container has the possiblility to refuse having another element added to it, e.g. because it has only limited "space". In that case the corresponding function would have a signature of insert :: a -> C a -> Maybe (C a). If an item can successfully be added, then the returned container will be less space avaiable. I'd like stuff and space to be symmetrical (maybe there lies the first flaw, because I can enumerate the elements, but I cannot enumerate the space). A symmetry like electrones and holes. I started like this data C a = C { insert :: a -> Maybe (C a), remove :: Maybe (a, C a) } but I could not implement anything sensible on top of this. I'd be happy to hear any comments on this, including loud thinking and random ramblings.

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Haskell safe ccalls
by Valentino Picotti 17 Dec '15

17 Dec '15

Hi everybody, I’m new on this list and have a newbie question about Haskell FFI and safe calls. I have written the following lines of C code that rely on the RTS: Condition* init_cond(){ Condition* c = malloc(sizeof(Condition)); initCondition(c); return c; } Mutex* init_mutex(){ Mutex* m = malloc(sizeof(Mutex)); initMutex(m); return m; } void wait_condition(Condition* condition, Mutex* mutex) { ACQUIRE_LOCK(mutex); if(!waitCondition(condition, mutex)){ fprintf(stderr, "A: Wait failed!"); }; RELEASE_LOCK(mutex); } And the Haskell program is written as follow: data Condition = Condition data Mutex = Mutex foreign import ccall "init_cond" init_cond :: IO (Ptr Condition) foreign import ccall "init_mutex" init_mutex :: IO (Ptr Mutex) foreign import ccall "wait_condition" wait_condition:: Ptr Condition -> Ptr Mutex -> IO () main :: IO () main = do c <- init_cond m <- init_mutex wait_condition c m putStrLn “Hello!” The behaviour that i want from my application is the same as the following C program: int main(int argc, char** argv){ pthread_cond_t c = PTHREAD_COND_INITIALIZER; pthread_mutex_t m; pthread_mutex_init(&m, 0); pthread_mutex_lock(&m); pthread_cond_wait(&c, &m); printf(“I didn’t block!\n"); pthread_mutex_unlock(&m); return 0; } What I expect is that the program doesn’t reach the putStrLn line, but it prints “Hello!” and terminates with exit code 0. I can’t figure out what’s going on under the hood. Can someone explain me what i’m missing? (I’m familiar with Capabilities, Tasks, Haskell threads) Thanks, Valentino P.

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Hyperlinked source docs
by Johannes Waldmann 16 Dec '15

16 Dec '15

As I said, I admire hyperlinked sources in the new "base" documentation https://hackage.haskell.org/package/base-4.8.1.0/docs/ and I want to know how I can produce such documents. What is the magic haddock/hscolour invocation? (I actually use standalone-haddock.) On hackage, not every package gets the special treatment? (In fact, only "base" does?) - J.W.

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IHaskell trouble, after upgrading to Haskell Platform 7.10.3?
by David Banas 16 Dec '15

16 Dec '15

Hi all, Are there any other IHaskell users out there, who are having trouble re-installing IHaskell, after upgrading to Haskell Platform 7.10.3? I’m getting this, at the tail end of the actual ihaskell build: [24 of 25] Compiling IHaskell.Eval.Info ( src/IHaskell/Eval/Info.hs, dist/build/IHaskell/Eval/Info.o ) [25 of 25] Compiling IHaskell.Publish ( src/IHaskell/Publish.hs, dist/build/IHaskell/Publish.o ) In-place registering ihaskell-0.8.3.0... Preprocessing executable 'ihaskell' for ihaskell-0.8.3.0... main/Main.hs:29:18: Could not find module ‘Data.String.Here’ It is a member of the hidden package ‘here-1.2.7@here_63mTmLx8Sz20TyEJBVCnnC’. Perhaps you need to add ‘here’ to the build-depends in your .cabal file. Use -v to see a list of the files searched for. Updating documentation index /Users/dbanas/Library/Haskell/share/doc/x86_64-osx-ghc-7.10.3/index.html cabal: Error: some packages failed to install: ihaskell-0.8.3.0 failed during the building phase. The exception was: ExitFailure 1 Thanks, and Happy Holidays! -db

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Parallel Haskell on RPi2
by spacestation＠venussociety.org 16 Dec '15

16 Dec '15

Hello to everone, Did anybody manage to install parconc-examples on a Raspberry Pi2 without the use of --force-reinstalls. As it would break to many packages on my end.I tried it the way describe from Simon Marlow s book "Parallel and concurrent programming in haskell". Or is there any option within cabal to seperate between new,new version and reinstall packages listed with pi@opencvrpi2:~/parconc-examples-master$ cabal install --only-dependencies I m using ghc 7.4.1 Thanks for any feedback Gottfried F. Zojer

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sum $ map f xs ... ghc-7.10 performance regression?
by Johannes Waldmann 15 Dec '15

15 Dec '15

Is there a difference between "sum $ map f xs" and "sum $! map f xs"? I would think no, since "$!" just evaluates the argument to WHNF, so it would evaluate just the first cons of the list. This little program main = print $ sum $ map bitcount [0, 4 .. 2^24-1 ] bitcount :: Int -> Int bitcount x = if x > 0 then let (d,m) = divMod x 2 in bitcount d + m else 0 runs in 1.6 seconds when compiled with -O2 on ghc-7.6.3, ghc-7.8.4, but takes 3.2 seconds on ghc-7.10.[1-3]. Why? when I change the main function (note: $ => $!) to main = print $ sum $! map bitcount [0, 4 .. 2^24-1 ] and compile with 7.10.[1-3], then it also runs in 1.6 seconds. (I can write a bug report but I want to check whether I am missing something obvious) - J.W.

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Does Backwards admit a Monad instance?
by David Feuer 15 Dec '15

15 Dec '15

In particular, I'm thinking about instance MonadFix m => Monad (Backwards m) where m >>= f = Backwards $ do fin <- forwards (f int) int <- forwards m return fin It looks to me like this should be valid, and compatible with the Applicative instance, but maybe I'm missing something.

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Re: [Haskell-cafe] Trouble installing ghc on CentOS 6
by Johannes Waldmann 15 Dec '15

15 Dec '15

I think that "--with-gmp-libraries" states the location of libgmp that the installed ghc will use when linking programs. Your error indicates that a .so file referenced from the executable (contained in the binary package) "utils/ghc-pwd/dist-install/build/tmp/ghc-pwd" could not be resolved. $ ldd utils/ghc-pwd/dist-install/build/tmp/ghc-pwd if it says ... libgmp.so.3 => not found then set LD_LIBRARY_PATH or check values in /etc/ld.so.conf and run /sbin/ldconfig - J.W.

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Trouble installing ghc on CentOS 6
by Lyle Kopnicky 14 Dec '15

14 Dec '15

Hi folks, I'm trying to install the 64-bit generic Linux distribution of ghc-7.10.3 on CentOS 6, as a non-privileged user in my home dir. I've unpacked the files, and I ran ./configure, but it told me it couldn't find libgmp.so.3. I searched for and found that library on the system. Looking at the help for ./configure, I saw the --with-gmp-libraries option, so I tried again with that, but it still can't seem to find the file: $ ./configure --prefix=/home/kopnicky/ghc --with-gmp-libraries=/usr/lib64 checking for path to top of build tree... utils/ghc-pwd/dist-install/build/tmp/ghc-pwd: error while loading shared libraries: libgmp.so.3: cannot open shared object file: No such file or directory configure: error: cannot determine current directory Strange, because that library is definitely there in /usr/lib64. Any thoughts on what I can try next? Thanks, Lyle

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