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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 04 Feb '08

04 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 04 Feb '08

04 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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IRC Statistics
by Vlad Dogaru 03 Feb '08

03 Feb '08

Hello, as part of an effort to learn Haskell, me and a few friends want to write an IRC statistcs generator. It would analyse logs and output HTML, text, or whatever other format. However, I have a few questions; we're all pretty new to this and it would be a shame to start off terribly wrong and get bored before we get to the fun parts. 1. Is there a similar effort in Haskell? I've seen a truly awesome IRCStats, but written in C (not that that's a bad thing). 2. I was thinking of the following structure: * a uniform Event format: joins, parts, actions, normal lines, and everything about them: the user, date and time, etc. * functions that parse logs to a list of events. Exotic log format? Just write a different function! (whatever `exotic' may mean) * functions that do various statistics on a list of events. The output will not be uniform. Examples are: who spoke most, what time people speak most, etc. * some way to make these into a common output form, maybe every above module having two functions, one for `internal' format, and one for converting that to proper output. Now, there will probably be a lot of opportunities to ask for feedback on possible statistics and log formats. My (main) question is whether you see anything conceptually wrong in this approach. With a bit of luck, we will be announcing hirst-0.1 in a few weeks or months (we're doing this while having schoool and other engagements). Thank you for your time, Vlad PS: This is my first post here, please point out any inadequacy. -- There is nothing more dangerous than an idea when it is the only one you have.

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ANN: strictify 0.1
by Sterling Clover 03 Feb '08

03 Feb '08

Dear Friend, Have you ever stared at a maze of Haskell code and thought "Gosh, I'm just feeling lazy today. Everything works, and I mainly understand the strictness characteristics of my program. But I just can't decide where to put those last few bangs. Maybe I don't need to micro-optimize anyway." Sure you have. It's ok. You can let it out. You're among friends here. Why, I bet you've even gone and sprinkled some bangs randomly, hoping for the best. We've all been there. Maybe you even got those pesky strictness annotations right, but a new version of GHC with its ever improving strictness analyzer came along and rendered some obsolete. And yet there they still lie, consuming whole tens of picoseconds worth of your hard-earned processor cycles and troubling your dreams. Well, friend, your dreams need be troubled no more. The time has come for a new era! The era of strictifiericization version 0.1. An era where you can kiss those micro-optimization troubles over silly shootout entries goodbye! Instead of brute-forcing your way through permutations of strictness entries let your computer do the work for you. That's why we invented them after all! Rather than putting "!" in just the right places, put "{- ! -}" in every place you _might_ want a strictness annotation. Then sit back, pop open a cool refreshing brew, and wait (and wait and wait) as strictify does the rest!* Available now now now at hackage: http://hackage.haskell.org/cgi-bin/ hackage-scripts/package/strictify-0.1 Darcs repository at: http://code.haskell.org/~sclv/strictify/ *To prevent exponential running time, strictify only produces a local rather than global optimum of strictness patterns, which should be sufficient in 99% of all cases. Strictify only works on POSIX- compliant systems. Strictify is currently only suitable for "shootout"-style executables which are contained in a single main file, accepting input from argv, stdin, or both. Strictify will not fully execute until it recieves an EOF in stdin. If you cannot produce an EOF through ctrl-D and are not streaming an input file in, you may be forced to run "echo "" | strictify". No guarantee is made, express or implied, as to strictify improving the speed of your program or your mental acuity regarding strictness. Offer void where prohibited. As strictify contains small parts, it is not suitable for children under the age of five. Do not ingest strictify more than seventy five times in a one hour period. If symptoms persist, consult your physician. --S

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more haskeem: it's just scheme in haskell now, no more "almost"
by Uwe Hollerbach 03 Feb '08

03 Feb '08

Hello, haskellers, my mud pies are getting bigger: I have added an exception-handling mechanism to haskeem (ie, for handling exceptions at the scheme level, not the haskell level; that was already working), and also hooked up the REPL to gnu readline: the example code for the readline command was practically tailor-made for me! :-) Also, I must apologize: I screwed up the URL earlier: I had said http://www.korgwal.com/software/haskeem/ and then promptly went and stuck it into http://www.korgwal.com/haskeem/ ... you may attribute that to rapidly-advancing senility, if you like, I won't contradict you. Anyway, I've fixed it by simply putting copies into both places. regards, Uwe Hollerbach

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