January 2010 - Libraries

RE: [Haskell-cafe] RE: ssh ports for monk and nun?
by Bayley, Alistair 22 Jan '10

22 Jan '10

> From: cristiano.paris(a)gmail.com > [mailto:cristiano.paris@gmail.com] On Behalf Of Cristiano Paris > > On Fri, Jan 22, 2010 at 11:38 AM, Bayley, Alistair > <Alistair.Bayley(a)invesco.com> wrote: > > ... > > Tried and failed. Our firewall will be closed to port 22 for the > > forseaable future. I'll give the OpenVPN thing a go, if I > can find some > > time. > > Trying to ask how to pierce your company's firewall in a public > mailing list, even from your company's email address, may not be > advisable. Well, I wasn't necessarily looking for that kind of advice, more along the lines of how to work with what I have (which is ports 80 and 443, via an http proxy server). I have been able to use CVS+SSH with sourceforge in the past, because they had cvs servers that listened for SSH connections on port 443. Alistair ***************************************************************** Confidentiality Note: The information contained in this message, and any attachments, may contain confidential and/or privileged material. It is intended solely for the person(s) or entity to which it is addressed. Any review, retransmission, dissemination, or taking of any action in reliance upon this information by persons or entities other than the intended recipient(s) is prohibited. If you received this in error, please contact the sender and delete the material from any computer. *****************************************************************

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darcs patch: lower base requirement down to base-2
by Sergei Trofimovich 22 Jan '10

22 Jan '10

Wed Dec 16 23:34:21 EET 2009 Sergei Trofimovich <slyfox(a)community.haskell.org> * lower base requirement down to base-2 At least ghc-6.6.1 is able to build it without problems. (package can be used in cabal-1.8, which is known to work on ghc-6.4+)

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darcs patch: fixed 'cabal sdist'
by Sergei Trofimovich 22 Jan '10

22 Jan '10

Tue Dec 15 00:56:45 EET 2009 Sergei Trofimovich <slyfox(a)community.haskell.org> * fixed 'cabal sdist' It actually fixes './configure' regeneration for such distros, like gentoo, wich had to patch configure.ac and regenerate script toolchain.

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darcs patch: System.Posix.Temp: improve haddocks for ... (and 2 more)
by gwern0＠gmail.com 22 Jan '10

22 Jan '10

Mon Jan 18 19:27:55 EST 2010 gwern0(a)gmail.com * System.Posix.Temp: improve haddocks for mkstemp to explain what that returned String actually is Mon Jan 18 19:30:22 EST 2010 gwern0(a)gmail.com * System.Posix.Temp: pad input filenames with 6 Xs If the argument doesn't terminate in capital Xs, the C mkstemp will simply bomb out with zero warning. This was not documented. By arbitrarily sticking a bunch of Xes at the end of all arguments, we guarantee that this exception will not be thrown, the type signature will not change, and no existing code can break (since if it was manually avoiding the exception by adding "XXX" itself, the temp files will now be simply 3 random characters longer, nothing worse). Mon Jan 18 19:34:37 EST 2010 gwern0(a)gmail.com * System.Posix.Temp: rm whitespace

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Make Happy Explicitly Depend on Perl
by Dominic Steinitz 22 Jan '10

22 Jan '10

Probably no-one has ever built happy on a machine without perl so this has never been noticed. I think it's more polite to fail at the configure stage rather than the build stage. In the cabal file I think we should have > build-tools: perl Here's a patch. Regards, Dominic.

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ssh ports for monk and nun?
by Alistair Bayley 22 Jan '10

22 Jan '10

Trying to get ssh working via putty from behind my company firewall. Had some success in the past with sourceforge because they had ssh daemons listening on ports 80 and 443, to aid prisoners like myself. Does anyone know if the monk (darcs.haskell.org) and nun (code.haskell.org) servers accept ssh on ports other than 22? Thanks, Alistair

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Recommended way to conditionally compile modules?
by Bryan O'Sullivan 19 Jan '10

19 Jan '10

I have a source base that contains a number of source files that use APIs that vary by platform: every platform provides select, most provide poll, BSDs provide kqueue, and Linux provides epoll. I already have autoconf tests for these functions, and I'd like to use the results of those autoconf checks to determine which modules to compile, but I am unable to figure out how to do this in my .cabal or .buildinfo file. (I *could* have explicit os conditionals in there, but that's ugly.) Right now, I'm just building all of the modules, and conditionally giving them bodies as follows: module System.Event.EPoll where #if defined(HAVE_EPOLL) ... #endif The trouble with this is twofold. I have to export everything in the module (because its contents vary depending on where I compile it), and the CPP macros there are ugly. Is there a better solution?

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Re: Iteratee (take, takeR): identical types, different signatures
by vvv＠mts.com.ua 14 Jan '10

14 Jan '10

On Thu, Jan 14, 2010 at 12:39 PM, Valery V. Vorotyntsev <valery.vv(a)gmail.com> wrote: > I've noticed inconsistency in type signatures of take* functions > (Data.Iteratee.Base). > > Compare > take :: (SC.StreamChunk s el, Monad m) => > Int -> EnumeratorN s el s el m a > with > takeR :: (SC.StreamChunk s el, Monad m) => > Int -> > IterateeG s el m a -> > IterateeG s el m (IterateeG s el m a) > > The latter type is equivalent to > takeR :: (SC.StreamChunk s el, Monad m) => > Int -> EnumeratorN s el s el m a > since > type EnumeratorN s_outer el_outer s_inner el_inner m a = > IterateeG s_inner el_inner m a -> > IterateeG s_outer el_outer m (IterateeG s_inner el_inner m a) > > `take' and `takeR' functions are almost similar: the only difference > is that `take' always consume all the stream while `takeR' can finish > early. > > Iteratee library should not obscure the fact that type signatures of these > functions are identical. Please consider replacing > IterateeG s el m (IterateeG s el m a) > with > EnumeratorN s el s el m a Dear John, I've refactored `take' and `takeR'. The changes are: - Int argument removed from `step' sub-function - null, length and splitAt belong ListLike (LL), not StreamChunk (SC) - consistent naming used in both functions (s/chk/s/, s/stream/str/) -----BEGIN PATCH----- -----END PATCH----- Code compiles. Proposed change does not affect semantics, AFAICT. I tested behavior with the following code snippet: -----BEGIN TEST----- module XXX where import Data.Iteratee import qualified Data.Iteratee as It test :: IO () test = sequence_ [ putStr (desc ++ " " ++ show n ++ " " ++ show c ++ "\t") >> runIter (joinI $ f n $ It.break (== c)) stream >>= print | n <- [7, 100], c <- "3cX", (f, desc) <- [(It.take, "take "), (takeR, "takeR")] ] where stream = Chunk "0123456789abcdef" -----END TEST----- PS: BTW, what does `R' suffix stand for (in takeR function name)? -- Best regards, vvv

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darcs patch: Control.Monad: +void :: f a -> f ()
by gwern0＠gmail.com 13 Jan '10

13 Jan '10

Fri Jan 8 16:44:55 EST 2010 gwern0(a)gmail.com * Control.Monad: +void :: f a -> f () See http://hackage.haskell.org/trac/ghc/ticket/3292 Turns m a -> m (). Lets one call functions for their side-effects without having to get rid of their return values with '>> return ()'. Very useful in many contexts (parsing, IO etc.); particularly good for 'forkIO' and 'forM_', as they demand return types of 'IO ()' though most interesting IO functions return non-().

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Adding an ignore function to Control.Monad
by Gwern Branwen 12 Jan '10

12 Jan '10

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA512 So while writing my wp-archivebot, I ran into the issue that forkIO requires IO () but returns IO ThreadId, and that many useful IO functions will return IO a instead of IO (). This forces some awkward contortions. Suppose I want to ping the WebCite website at a particular address, and this request makes WebCite archive a URL embedded in that address. Presumably I could venture into the depths of Network.HTTP to figure out how to ping an URL without also pulling down the server's HTML, but why do that when I already have obviously 'openURL :: String -> IO String'? Much easier to do something like 'openURL "webcite.org" ++ foo ++ "other stuff" '. But my bot needs to handle quite a few URLs; one at a time, what with all the waits and timeouts, isn't going to hack it. So for a given link, I forkIO the openURL request. But of course, forkIO demands IO (), so I toss in a '>> return ()'. Fair enough. So I examine the performance, and it's still too slow. Recent Changes has hundreds of different pages a minute. I'd better fork each page (and then fork for each link). But wait, all those forkIOs are returning IO ThreadIds, and my top-level forkIO call demands IO ()... So another >> return (). At this point, the code is starting to look pretty silly - something like '...stuff >> return ()) >> return ())'. So I see the repeated pattern, and by the rule of 3, factor it out to: - -- | Convenience function. 'forkIO' and 'forM_' demand return types of 'IO ()', but most interesting - -- IO functions don't return void. So one adds a call to 'return ()'; this just factors it out. ignore ∷ (Monad m) ⇒ m a → m () ignore x = x >> return () Not the most complex convenience function I've ever written, but not any simpler than, say Control.Monad.forever or for that matter, most of the stuff in Control.Monad. I'd think it'd be useful for more than just me. Agda is lousy with calls to '>> return ()'; and then there's ZMachine, arrayref, whim, the barracuda packages, binary, bnfc, buddha, bytestring, c2hs, cabal, chesslibrary, comas, conjure, curl, darcs, darcs-benchmark, dbus-haskell, ddc, dephd, derive, dhs, drift, easyvision, ehc, filestore, folkung, geni, geordi, gtk2hs, gnuplot, ginsu, halfs, happstack, haskeline, hback, hbeat... You get the picture. I realize the specific name of 'ignore' can be bikeshedded to death, but it's clear, it's short, Hoogle turns up one other function with ignore in its name (Distribution.ParseUtils ignoreUnrec), and it's been independently named 'ignore' by another Haskeller (lilac). Existing uses of the string 'ignore are rare - it's in a few places as a variable, cabal and cabal-install and ehc and tar have where definitions of an ignore, a test for directory defines an ignore and imports Control.Monad unqualified, fit defines an 'ignore' but doesn't seem to use it in any module that also imports Control.Monad unqualified, halipeto defines an ignore but doesn't import Control.Monad, shim/yi has a let definition of an ignore, yhc has a where definition of an ignore. And that's about it. One of directory's tests would break, and the rest might have an additional -Wall warning. - -- gwern -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.9 (GNU/Linux) iEYEAREKAAYFAkov5Q0ACgkQvpDo5Pfl1oIsRQCghUqynThzcT+OYV1KaYJhGFhv 6yYAnjf7CVOm0+Fg1FBa9IpdVIrRpCZm =Cd8V -----END PGP SIGNATURE-----

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