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ANNOUNCE: dzen-utils 0.1
by Felipe Lessa 15 Mar '09

15 Mar '09

Hello! I'm please to announce dzen-utils 0.1. I don't feel like it is ready to be released, but let's see how everything goes. :) == WHAT == dzen-utils contains various utilities for creating dzen input strings in a type-safe way using some combinators, including the ability to apply colors locally (instead of applying for everything beyond some point). It can also emulate dbar and gdbar, do automatic padding, and more. == WHY == I don't like to write bash scripts for dzen, and I don't like the way xmobar treats its configuration and its inability to show anything other than text. This package is a short-term solution for my problems. Maybe I'll write xmozen in the future. ;) == WHERE, HOW, etc. == It is in Hackage already, go get it[1]. Please see the documentation of System.Dzen for some small examples. [1] http://hackage.haskell.org/cgi-bin/hackage-scripts/package/dzen-utils Thanks for your time, -- Felipe.

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How to catch error in array index when debugging
by Colin Paul Adams 15 Mar '09

15 Mar '09

I'm getting a runtime failure "Error in array index". This causes ghci to exit. Is there a way to get it to break instead, so I can find out which function is failing? -- Colin Adams Preston Lancashire

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Re: [Haskell-cafe] Default Tuple Orderings
by Martijn van Steenbergen 15 Mar '09

15 Mar '09

Mark Spezzano wrote: > In other words my best guess is that the ordering of tuples is by > comparing the first tuple elements and then the seconds, thirds etc, > until there’s an element less than another. ...until there's an element not equal to the other, yes. It finds the first position at which the two elements in the tuples are unequal and returns the result of comparing those two elements (LT or GT). If there's no such position, then the tuples are equal. See also: http://en.wikipedia.org/wiki/Lexicographical_order HTH, Martijn.

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is there a version of hsffig that builds on a recent versin of haskell?
by Anatoly Yakovenko 15 Mar '09

15 Mar '09

is there a version of hsffig that builds on a recent versin of haskell?

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Default Tuple Orderings
by Mark Spezzano 15 Mar '09

15 Mar '09

Hi, Does anyone know how Haskell’s tuple ordering works? Presumably for some tuple T1 (x1,x2,...xn) and another tuple T2 (y1,y2,...yn) Haskell would compare T1 and T2 as follows: T1 < T2 if: x1 < y1 OR otherwise if x1 == y1 then if x2 < y2 OR otherwise if x2 == y2 then if x3 < y3 OR otherwise etc xn < yn OR otherwise both tuple are equal In other words my best guess is that the ordering of tuples is by comparing the first tuple elements and then the seconds, thirds etc, until there’s an element less than another. Is this reasoning correct? So minimum xs would yield the “smallest” tuple (according to the above rules and if xs is a list of tuples)? Cheers, Mark Spezzano No virus found in this outgoing message. Checked by AVG. Version: 7.5.557 / Virus Database: 270.11.13/2001 - Release Date: 14/03/2009 6:54 AM

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A systematic method for deriving a defintion of foldl using foldr?
by R J 15 Mar '09

15 Mar '09

foldl and foldr are defined as follows: foldr :: (a -> b -> b) -> b -> [a] -> b foldr f e [] = e foldr f e (x : xs) = f x (foldr f e xs) foldl :: (b -> a -> b) -> b -> [a] -> b foldl f e [] = e foldl f e (x : xs) = foldl f (f e x) xs 1. I understand how these definitions work, and yet I'm unable to implement foldl in terms of foldr. What's a systematic approach to identifying such an implementation, and what is the implementation? 2. I believe that the reverse implementation--namely, implementing foldr in terms of foldl--is impossible. What's the proof of that? 3. Any advice on how, aside from tons of practice, to develop the intuition for rapidly seeing solutions to questions like these would be much appreciated. The difficulty a newbie faces in answering seemingly simple questions like these is quite discouraging. _________________________________________________________________ Express your personality in color! Preview and select themes for Hotmail®. http://www.windowslive-hotmail.com/LearnMore/personalize.aspx?ocid=TXT_MSGT…

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Alternative to Data.Binary
by Grzegorz Chrupala 15 Mar '09

15 Mar '09

Hi all, Is there a serialization library other than the Data.Binary from hackage? I am using Data.Binary in a couple of projects, but I have found its stack and memory usage very hard to control. Its very common that decoding a map or list of non-trivial size uses up all available RAM, or causes a stack overflow. I don't care that much about it being extremely fast, I just want to stop worrying that if I try to read a file a few percent larger than the last time, my program will suddenly stop working. Best, -- Grzegorz -- View this message in context: http://www.nabble.com/Alternative-to-Data.Binary-tp22512229p22512229.html Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com.

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RE: Hashing over equivalence classes
by Galchin, Vasili 15 Mar '09

15 Mar '09

Hi Roman, So are you really talking about an equivalence relation on the function's domain? The reason I ask is that it is well known that "f(a)=f(b)" establishes an equivalence relation on f's co-domain! Vasili

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Does anybody dislike implicit params as much as I do?
by Thomas Hartman 15 Mar '09

15 Mar '09

http://blog.patch-tag.com/2009/03/09/implicitparams-are-evil-thoughts-on-ad… I understand there are arguments for using IPs, but after this experience, the ImplicitParams extension is a "code smell" for me.

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Style Guide for Haskell Code
by Manlio Perillo 14 Mar '09

14 Mar '09

After a quick search with Google, it seems that there is not yet an "official" document for Style Guide for Haskell Code. I was only able to found: http://www.cs.caltech.edu/courses/cs11/material/haskell/misc/haskell_style_… http://urchin.earth.li/~ian/style/haskell.html http://github.com/tibbe/haskell-style-guide/tree/master and, of course, the GHC style guide. Any plans for a common document? Thanks Manlio Perillo

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