June 2011 - Glasgow-haskell-users

partially applied type synonyms
by Arie Peterson 05 Mar '12

05 Mar '12

Dear list, Is there a good reason that partially applied type synonyms cannot be made instances of classes? - A simple example would be making the identity type 'Id' ("type Id x = x") instance of 'Monad'. This would eliminate the need for some silly occurrences of 'runIdentity', and perhaps narrow the gap between monads and monad transformers. - The reason I complain about this now is a more involved example, where introducing a newtype to work around the restriction is not an option. Well, not as far as I can see now, anyway. Partially applied type synonyms are, in a sense, the anonymous functions at the type level, and one might argue that they deserve the same 'first-class member status' as the lambda at the value level. Kind regards, Arie Peterson

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Proposal to incorporate Haskell.org
by Don Stewart 16 Dec '11

16 Dec '11

Hello everyone. The haskell.org committee[1], in the interest of the long-term stability of the open source Haskell community infrastructure, has decided to incorporate haskell.org as a legal entity. This email outlines our recommendation, and seeks input from the community on this decision. The committee's proposal is that haskell.org incorporate as an entity under the Software Freedom Conservancy umbrella organization (the same group that Darcs joined recently): http://sfconservancy.org/ If we proceed with this move, haskell.org will be a legal entity, and registered as a non-profit, allowing us to more directly accept (US tax-deductible) donations, and to invest in assets that benefit the Haskell open source community. We welcome your feedback on the proposal attached below. -- Don Stewart (on behalf of the Haskell.org committee) ------------------------------------------------------------------------ = A proposal for the incorporation of Haskell.org = In recent years, haskell.org has started to receive assets, e.g. money from Google Summer Of Code, donations for Hackathons, and a Sparc machine for use in GHC development. We have also started spending this money: in particular, on hosting haskell.org itself. There is also interest in running fundraising drives for specific things such as Hackathon sponsorship and hosting fees. However, haskell.org doesn't currently exist as a legal entity, meaning that these assets have had to be held on our behalf by other entities, such as Galois and various universities. This leads to tricky situations, with no-one being sure who should decide how the haskell.org assets can be used. To solve these problems, we propose that haskell.org applies to become a member project of the Software Freedom Conservancy (SFC) <http://conservancy.softwarefreedom.org/>. The SFC is a non-profit organization that provides free financial and administrative services to open source projects. Additionally, it has 501(c)(3) status, meaning donations from the US are tax-deductible. The SFC would hold haskell.org's money and other assets, and would be able to accept donations on behalf of haskell.org. The haskell.org committee, as described here [2], will make decisions on spending assets and other decisions related to governing the non-profit. Before proceeding, we are inviting input from the community in the form of specific objections or queries regarding the plan. We've tried to answer some of the most likely questions: Q: Does this mean that my Haskell project must now be covered by a copyleft licence such as GPL? A: No, but Haskell projects using haskell.org resource should use an Open Source licence <http://www.opensource.org/licenses/alphabetical>. Q: Will it still be possible to use community.h.o to host non-open-source material, such as academic papers? A: An overall minority of such content, as is the current situation, is not a problem. Q: Will it still be possible to have job ads on the haskell.org mailing lists and website? A: Yes. Q: Will this affect our ability to host the Haskell Symposium <http://www.haskell.org/haskell-symposium/> and Industrial Haskell Group<http://industry.haskell.org/> webpages within haskell.org? A: No. Q: What will be the relationship between haskell.org and other organizations such as the Haskell Symposium and Industrial Haskell Group? A: Those organisations will continue to exist as separate entities. Q: If an umbrella non-profit organisation "The Haskell Foundation" was created, would haskell.org be able to join it? A: Yes. It's likely that in such a scenario, the Haskell Foundation would become the owner of the haskell.org domain name, with the cost divided between the members. The entity that is part of the SFC would be renamed "community.haskell.org" in order to avoid confusion. [1]: http://www.haskell.org/haskellwiki/Haskell.org_committee [2]: http://www.haskell.org/haskellwiki/Haskell.org_committee#Operation

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Quoting a quasi-quote
by Yitzchak Gale 27 Jul '11

27 Jul '11

It was pointed out by Ben Millwood on the Cafe that there is an undocumented way to escape the closing oxford bracket of a quasi-quote using a backslash: [s|This quasi-quote contains this, \|], an escaped closing oxford bracket.|] The backslash itself cannot be escaped in this way: [s|Also contains an escaped bracket \\|] |] Thus there is a fairly strong limitation on the contents of a quasi-quote: it can never end in a backslash. This behavior is not mentioned in the GHC docs. Is it a mistake, or is it meant to be a supported feature? This behavior is a bit surprising to me. Since the whole point of a quasi-quoter is to allow the user to define syntax, you would think that the syntax for the quasi-quote itself would be as quiet as possible and stay out of the way. People who need to be able to escape the closing bracket can easily define their own syntax to do so. In any case, if this is indeed a feature, it certainly should be documented. Thanks, Yitz

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Network.HaskellNet.IMAP over SSL connection
by HP Wei 29 Jun '11

29 Jun '11

I tried to use Network.HaskellNet.IMAP to read emails and failed: user error (NO: Plaintext authentication disallowed on non-secure (SSL/TLS) connections.) Any solution for reading emails over SSL connection ?? thanks HP

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Testsuite failures and some easy fixes
by Daniel Fischer 28 Jun '11

28 Jun '11

Today's HEAD produced 49 unexpected failures, most of which are caused by trivia. - tcrun006 and tcrun029 use datatype contexts which were removed from HEAD (7 ways each), can be fixed by adding a language pragma (cf. also http://hackage.haskell.org/trac/ghc/ticket/5229) - ghcpk01.stdout hasn't yet been updated to include the new trusted field - ffi005 fails to compile (7 ways) due to an ambiguous occurrence of unsafePerformIO (Foreign and System.IO.Unsafe) - cg005 and T4059 have unexpected stderr due to a warning about unsafePerformIO going to be removed from Foreign - T4437 fails to compile due to a type change: T4437.hs:9:39: Couldn't match expected type `(String, CmdLineParser.FlagSafety, ExtensionFlag, DynFlags.TurnOnFlag -> DynFlags.DynP ())' with actual type `(t0, t1, t2)' In the pattern: (ext, _, _) In a stmt of a list comprehension: (ext, _, _) <- xFlags In the expression: [ext | (ext, _, _) <- xFlags] Those are easily fixed by the attached patches (but some may need a more principled fix). Further, 17 unexpected failures are due to hpc output being formatted differently from the expectation (5x hpc_fork, 6x hpc001, 6x tough). Two unexpected failures (T4809, cgrun068) are due to mtl not being built the dyn way. The remaining 5 are - T4801 (allocating too little because there are fewer Generic instances for tuples) - dph-diophantine-opt (3 ways) - dph-words-opt On my 32-bit box, also T3294 unexpectedly fails since about a week ago due to too little allocation (a bit below 690M, minimum allowed 800M). If that's reproducible and not known to be temporary, the bounds should be adjusted. Cheers, Daniel

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Hoopl: Combining CheckingFuelMonad with State?
by Justin Bailey 27 Jun '11

27 Jun '11

I'd like to carry around some state when rewriting. It seems like CheckingFuelMonad, etc. are set up to use with other monads but I can't get the types to agree. Using MTL I've managed to come up with these types: > newtype RewriteOnce a = R (State Bool a) > deriving (Monad) > > instance MonadState s (CheckingFuelMonad RewriteOnce) where > get = undefined > put = undefined But I cannot write the definitions for get and put. Is this possible or am I misundersanding CheckingFuelMonad? Is there a better approach altogether? Thanks in advance for any help! Justin

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GHC HEAD broken on OS X
by austin seipp 27 Jun '11

27 Jun '11

After doing a 'git pull origin master && ./sync-all pull origin master', I get the following build failure when stage1 attempts to compile the RTS code: http://paste.debian.net/121097/ A quick glance at the errors seem to indicate this work is related to the new events stuff for GHC. Duncan was working on this last I think - is anybody else experiencing this failure? -- Regards, Austin

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Experiencing libffi related problem with GHC HEAD on Ubuntu 11.04
by Ryan Newton 27 Jun '11

27 Jun '11

Has anyone seen this one before? # libffi.so needs to be built with the correct soname. # NOTE: this builds libffi_convience.so with the incorrect # soname, but we don't need that anyway! cd libffi && \ "cp" build/libtool build/libtool.orig; \ sed -e s/soname_spec=.*/soname_spec="libHSffi-ghc7.1.20110609.so<http://libhsffi-ghc7.1.20110609.so/>"/ build/libtool.orig > build/libtool cp: cannot stat `build/libtool': No such file or directory sed: can't read build/libtool.orig: No such file or directory make[2]: *** [libffi/stamp.ffi.configure] Error 2 make[1]: *** [all_libffi] Error 2 make[1]: Leaving directory `/home/newton/build/haskell2/ghc-validate' make: *** [all] Error 2 Thanks, -Ryan P.S. It's not new. I just did a "git pull origin master && ./sync-all pull origin master" and got this error but I also got the same error on this machine back on June 9th. However, this package has built GHC HEAD in the past. It has the standard ubuntu libffi-dev and libffi5 packages installed.

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gitweb on darcs.haskell.org?
by Iavor Diatchki 26 Jun '11

26 Jun '11

Hello, Do we have an instance of "gitweb" for the various ghc related repos running somewhere? If not, I'd be happy to setup an instance, would anyone object? "gitweb" is a web-interface which makes it easy to get a quick overview of what's going on with a collection of repositories. It shows commits, branches, tags, etc. Also, it provides RSS/Atom feeds, which makes it easy to subscribe to changes for repos of interest. -Iavor PS: you can try it out locally by typing "git instaweb" in a git repository.

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Hoopl: Examples of wrapFR or wrapBR?
by Justin Bailey 25 Jun '11

25 Jun '11

Can someone provide an example of how to use wrapFR/wrapBR? I know they are deprecated, but I would really like to see them in action if they are used anywhere at all ... Thanks so much! Justin

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