February 2008 - Haskell-Cafe

Re: [Haskell-cafe] building the unix package and cabal
by Thomas Schilling 04 Feb '08

04 Feb '08

This is the GNU Multi-Precision library. You have to install that separately, Cabal can't do that for you. You should use the redhat package manager to install it. HTH On Feb 4, 2008 4:43 PM, Galchin Vasili <vigalchin(a)gmail.com> wrote: > Hi Thomas, > > Have you tried to build this package yourself? I get a linker error .. > unresolved symbol "gmp". > > Vasili > > > > > On 2/4/08, Thomas Schilling <nominolo(a)googlemail.com> wrote: > > Build-type: Configure means that *Cabal uses ./configure * to build > > the package. Nothing changes for you. Just use the usual: > > > > runhaskell Setup.hs configure --prefix=... [--user] > > runhaskell Setup.hs build > > runhaskell Setup.hs install > > > > or with cabal-install: > > > > cabal install unix > > > > 2008/2/4 Galchin Vasili <vigalchin(a)gmail.com>: > > > Hello, > > > > > > I have been trying to build the unix package on RedHat RHEL 5. > Over > > > the weekend I read through the Cabal documentation. The unix-2.2.0.0 > > > unix.cabal specifies the "build-type" attribute as "Configure". Based on > > > Cabal doc, I should run ./configure. After this step then what? Bottom > line > > > is how do I build the unix-2.2.0.0 package on RHEL 5? > > > > > > Thank you, Vasili > > > _______________________________________________ > > > Haskell-Cafe mailing list > > > Haskell-Cafe(a)haskell.org > > > http://www.haskell.org/mailman/listinfo/haskell-cafe > > > > > > > > > >

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building the unix package and cabal
by Galchin Vasili 04 Feb '08

04 Feb '08

Hello, I have been trying to build the unix package on RedHat RHEL 5. Over the weekend I read through the Cabal documentation. The unix-2.2.0.0 unix.cabal specifies the "build-type" attribute as "Configure". Based on Cabal doc, I should run ./configure. After this step then what? Bottom line is how do I build the unix-2.2.0.0 package on RHEL 5? Thank you, Vasili

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Circular enums
by Ben Butler-Cole 04 Feb '08

04 Feb '08

[Resend with formatting maybe fixed.] Hello I'm trying to define functions that allow you to traverse a bounded enumeration, "wrapping" at the start and the end. My implementation looks like this: next, prev :: (Enum a, Bounded a) => a -> a next = turn 1 prev = turn (-1) turn :: (Enum a, Bounded a) => Int -> a -> a turn n e = toEnum (add (fromEnum (maxBound::a) + 1) (fromEnum e) n) where add mod x y = (x + y + mod) `rem` mod Which fails to type check under GHC with this error: No instance for (Bounded a) arising from use of `maxBound' at Hbot.hs:6:34-41 Probable fix: add (Bounded a) to the expected type of an expression In the expression: maxBound :: a In the first argument of `fromEnum', namely `(maxBound :: a)' In the first argument of `(+)', namely `fromEnum (maxBound :: a)' My (clearly flawed) understanding of the signature I've specified for 'turn' means *exactly* that a is Bounded. Can anyone enlighten me as to where my understanding is going awry and how (whether) I can achieve what I'm trying to do. Thank you Ben

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ANN: heap-0.2
by Stephan Friedrichs 04 Feb '08

04 Feb '08

A flexible heap implementation supporting min-, max- and custom-ordered heaps. New features since version 0.1: - Foldable and Read instance - filter, partition - subrange functions: take, drop, splitAt, takeWhile, span, break http://hackage.haskell.org/cgi-bin/hackage-scripts/package/heap-0.2.1 //Stephan -- Früher hieß es ja: Ich denke, also bin ich. Heute weiß man: Es geht auch so. - Dieter Nuhr

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parsec3 pre-release [important note]
by Derek Elkins 04 Feb '08

04 Feb '08

I forgot to mention that the Text.Parsec modules should be preferred to the Text.ParserCombinators.Parsec modules as the Haddock documentation reveals.

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ANN: bimap 0.1 - a bidirectional map
by Stuart Cook 04 Feb '08

04 Feb '08

Data.Bimap is a data structure that represents a bidirectional mapping between two key types. A bimap has two type parameters; each value in the bimap is associated with exactly one value of the opposite type. In other words, it's a bijection between (subsets of) its argument types. The API is loosely based on Data.Map; feedback and suggestions are most welcome. So far I've only tested it on GHC 6.6 on Linux/x86, with Cabal 1.2.3.0. Let me know if it works or breaks on other configurations. Hackage: http://hackage.haskell.org/cgi-bin/hackage-scripts/package/bimap-0.1 Haddocks: http://code.haskell.org/~scook0/haddock/bimap/ Darcs: darcs get http://code.haskell.org/bimap Stuart Cook

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Cabal, GHC, FFI and Visual Studio on Windows
by Magnus Therning 04 Feb '08

04 Feb '08

Is it possible to get Cabal to use 'cl' (Microsoft's C/C++ compiler shipped with Visual Studio Express)? I've found the Wiki page on using Visual Studio to create a DLL, then convert it to a .a file so that GHC can consume it. I'd rather skip using Visual Studio to build things and just ship a Cabalised package. /M -- Magnus Therning (OpenPGP: 0xAB4DFBA4) magnus＠therning．org Jabber: magnus．therning＠gmail．com http://therning.org/magnus What if I don't want to obey the laws? Do they throw me in jail with the other bad monads? -- Daveman

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Who started 42, and when?
by Anthony Clayden 03 Feb '08

03 Feb '08

The earliest use of 42 in English humour I know of is Lewis Carroll's "Hunting of the Snark", written 1874 when the author was aged 42. Wikipedia says it all, and refers to Martin Gardner's "The Annotated Snark" (which is excellent). Lewis Carroll is the pen name of Charles Dodgson - a mathematician/logician. Gardner is of course a mathematician/science writer with an interest in puzzles and paradoxes. So although both rather pre-date functional programming, I think we might say there's a similar streak of humour. Sadly, Douglas Adams never revealed what language 'Deep Thought' was programmed in, but perhaps the machine it was 'unworthy to design' was to run Haskell natively? Anthony > The arbitrary constant was made popular by Douglas Adams in > the mid-1970s radio series ``A Hitchhikers Guide to the Galaxy'' (a > trilogy in 4 parts) --- however it does have a basis in the standard > model of physics --- a paper in Phys.Rev. of the early 1970s > described the unification of the Electro-Weak and Strong nuclear > forces --- the arbitrary constant (of nearly) 42 appears in the > calculations. I forget the original paper but if you get hold of > Frank Close ``The Cosmic Onion'' a graph reproduces the result. I met > Douglas Adams once at a book signing and asked him how he got hold of > the Phys.Rev. paper so early. Technically he should have written that > ``42 is the answer to life, the universe and everything except for > gravity and a few other arbitrary constants'' > > Adams was interested in computing --- I think his reaction to being > told about functional programming was to wonder what non-functional > programming might be.

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Who started 42, and when?
by Loup Vaillant 03 Feb '08

03 Feb '08

I have read quite a lot of Haskell papers, lately, and noticed that the number 42 appeared quite often, in informal tutorials as well as in very serious research papers. No wonder Haskell is the Answer to The Great Question of Life, The Universe, and Everything, but I would like to know who started this, and when. Google wasn't much help, and I can't believe it's coincidence --hence this email. I hope I didn't opened some Pandora box. :-) Cheers, Loup

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Poor libraries documentation
by Neil Mitchell 03 Feb '08

03 Feb '08

Hi, I went looking for the the function in Haskell to calculate cos^{-1}, inverse cosine. Unfortunately, the poor documentation in the libraries hampered my attempts. The documentation for the trig functions in Haskell is completely non-existent: http://haskell.org/ghc/docs/latest/html/libraries/base/Prelude.html#v%3Acos For a start, its probably a good idea to mention that cos is an abbreviation of cosine (most people will know, but its handy to state it). Secondly, and much more importantly, it should state whether these measurements are in degrees or radians. It should also state things like acos is the inverse of cos - its been a while since I last used trig and I had to look it up!!! We are also lacking documentation for things like odd/even, which are obvious enough, but its nice to say that they meet the intuition. Could haddock be extended to give a warning message (in -Wall mode perhaps) when an exported function has no comment associated with it? This would be a really nice project for someone to take on, and very much appreciated :-) Thanks Neil

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