[Haskell-cafe] Which builder to choose?
Hi, I'm looking at the packages blaze-builder and bytestring, and both provide builders for ByteString. Which one should I use? In which situations is one more convenient than the other? Thanks for the help. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] future (editor) of HCAR?
I would be delighted to take the full responsibility (or just help) in the HCAR. I have some ideas, maybe I could get some time later to write them down. 2013/9/18 Janis Voigtlaender j...@informatik.uni-bonn.de Dear all, The Haskell Communities and Activities Report has been produced twice a year for more than ten years now: http://www.haskell.org/**haskellwiki/Haskell_**Communities_and_Activities_ **Reporthttp://www.haskell.org/haskellwiki/Haskell_Communities_and_Activities_Report I have been responsible for producing it the last few years, which was fun. I am now looking to pass that on, handing over the HCAR to someone else. Any takers? Editing HCAR is a few days work per year, but it is also a great way to be involved in the Haskell community - you get a lot of news first hand. There are various procedures in place that automate some of the work, and if someone is interested in taking over, I'm very willing to help along, for example producing the next edition of the report together for a smooth transition. Below I attach the previous call for contributions, which also answers some basic questions about the report. For further questions about the process etc., anybody interested simply get in touch with me. Also, such a transition is a good opportunity to rethink model and processes. Maybe you (anybody on the mailing list) have completely new ideas for how the HCAR should be organized? How it could function better? What other purposes it could serve than it has so far? ... (Or even that HCAR in its existing form is not needed anymore, but could be replaced by something great new?) Best, Janis. Original-Nachricht Betreff: Call for Contributions - Haskell Communities and Activities Report, May 2013 edition Datum: Mon, 08 Apr 2013 21:56:19 +0200 Von: Janis Voigtländer j...@informatik.uni-bonn.de An: Haskell hask...@haskell.org Dear all, I would like to collect contributions for the 24th edition of the ==**==** Haskell Communities Activities Report http://www.haskell.org/**haskellwiki/Haskell_**Communities_and_Activities_ **Reporthttp://www.haskell.org/haskellwiki/Haskell_Communities_and_Activities_Report Submission deadline: 1 May 2013 (please send your contributions to hcar at haskell.org, in plain text or LaTeX format) ==**==** This is the short story: * If you are working on any project that is in some way related to Haskell, please write a short entry and submit it. Even if the project is very small or unfinished or you think it is not important enough --- please reconsider and submit an entry anyway! * If you are interested in an existing project related to Haskell that has not previously been mentioned in the HCAR, please tell me, so that I can contact the project leaders and ask them to submit an entry. * Feel free to pass on this call for contributions to others that might be interested. More detailed information: The Haskell Communities Activities Report is a bi-annual overview of the state of Haskell as well as Haskell-related projects over the last, and possibly the upcoming six months. If you have only recently been exposed to Haskell, it might be a good idea to browse the previous edition --- you will find interesting projects described as well as several starting points and links that may provide answers to many questions. Contributions will be collected until the submission deadline. They will then be compiled into a coherent report that is published online as soon as it is ready. As always, this is a great opportunity to update your webpages, make new releases, announce or even start new projects, or to talk about developments you want every Haskeller to know about! Looking forward to your contributions, Janis (current editor) FAQ: Q: What format should I write in? A: The required format is a LaTeX source file, adhering to the template that is available at: http://haskell.org/**communities/05-2013/template.**texhttp://haskell.org/communities/05-2013/template.tex There is also a LaTeX style file at http://haskell.org/**communities/05-2013/hcar.styhttp://haskell.org/communities/05-2013/hcar.sty that you can use to preview your entry. If you do not know LaTeX, then use plain text. If you modify an old entry that you have written for an earlier edition of the report, you should already have received your old entry as a template (provided I have your valid email address). Please modify that template, rather than using your own version of the old entry as a template. Q: Can I include Haskell code? A: Yes. Please use lhs2tex syntax (http://people.cs.uu.nl/** andres/lhs2tex/ http://people.cs.uu.nl/andres/lhs2tex/). The report is compiled in mode polycode.fmt.
Re: [Haskell-cafe] resources on static analysis
If you are interested in general program analysis, I recommend you the book Principles of Program Analysis ] http://www.amazon.com/Principles-Program-Analysis-Flemming-Nielson/dp/3540654100]. It's very complete, and covers the most important kind of analyses that you can do (data-flow, constraint-based, abstract interpretation and type-and-effect systems - the latter is the nearest to Haskell). If you are interested in analyses that infer relations such as the one shown above, you can check at size and cost analyses. Here are some pointers: - RAML [http://raml.tcs.ifi.lmu.de/] is based on ML, and includes in its types information about the memory used by each function, - The PhD thesis of Vasconcelos [ http://www.ncc.up.pt/~pbv/research/PB_Vasconcelos_PhD_thesis.pdf] uses types with sizes to infer relations between the sizes of the arguments in a call. It uses Haskell, so it may be the most relevant one, - In my group we've done some work about size and resource analysis [ http://arxiv.org/abs/1308.3940]. It's Prolog-based, but the ideas are general and could be applied to your case. 2013/9/10 Ian Ross i...@skybluetrades.net Not specifically about Haskell, but I read some lecture notes on this topic yesterday (by Michael Schwartzbach, PDF here: http://lara.epfl.ch/web2010/_media/sav08:schwartzbach.pdf). The notes do a good job of explaining how you set up lattices for various kinds of analyses, and how calculating fixed points over those lattices can yield various sorts of interesting information. Most of the examples are based on a simple imperative language, but much of the analysis is applicable to Haskell as well. On 10 September 2013 13:15, Maarten Faddegon haskell-c...@maartenfaddegon.nl wrote: Dear list, I am interested in learning more about static analysis of Haskell code. Specifically of the relation between arguments of recursive and non-recursive calls. For example if we look at the ++ function from Prelude: (++) [] ys = ys (++) (x:xs) ys = x : xs ++ ys amongst others, we could infer the relations: ys_i+1 = ys_i (x:xs)_i+1 = xs_i Searching the web I found several tools (HLint, Haskabelle, Sourcegraph), but I am interested in the theory behind this. If you could recommend a paper or a book on this topic I would be grateful. Thanks, Maarten Faddegon __**_ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/**mailman/listinfo/haskell-cafehttp://www.haskell.org/mailman/listinfo/haskell-cafe -- Ian Ross Tel: +43(0)6804451378 i...@skybluetrades.net www.skybluetrades.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] GHC API + Cabal API + Cabal version checks: is there a way out?
I'm willing to help in the process, if some directions were given to me on how to tackle this problem. In any case, for me is seems fine to have a dependency from cabal to ghc, the only problem is the converse: ghc depending on cabal. Is this right? 2013/9/6 Herbert Valerio Riedel h...@gnu.org On 2013-09-06 at 15:13:58 +0200, Yuri de Wit wrote: I spent some time looking into the touch points between ghc and cabal in the past, and the first oddity i saw was a direct dependency from ghc to the cabal sources. After taking a closer look it seems that ghc shares some common, low level modules with cabal that didnt seem to justify the whole dependency. The right solution, imho, is to review these dependencies and move the low level ones out into a separate package that is shared by both ghc and cabal and that will rarely change. The direct side effect of this is that ghc would not be tied directly to a specific cabal version and you would not have to deal with this issue. [...] fyi, a similiar/related discussion took place few months ago on ghc-devs: http://www.haskell.org/pipermail/ghc-devs/2013-March/000800.html hth, hvr ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Tutorial on JS with Haskell: Fay or GHCJS?
Hi, I'm currently writing a tutorial on web applications using Haskell. I know the pros and cons of each server-side library (Yesod, Snap, Scotty, Warp, Happstack), but I'm looking for the right choice for client-side programming that converts Haskell to JavaScript. I've finally come to Fay vs. GHCJS, and would like your opinion on what's the best to tackle. My current list of pros and cons is: Fay === Pros: - Does not need GHC 7.8 - Easy FFI with JS - Has libraries for integration with Yesod and Snap Cons: - Only supports a subset of GHC (in particular, no type classes) GHCJS == Pros: - Supports full GHC - Easy FFI with JS - Highly opinionated point: will stay longer than Fay (but it's very important for not having a tutorial that is old in few months) Cons: - Needs GHC 7.8 (but provides a Vagrant image) ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Tutorial on JS with Haskell: Fay or GHCJS?
I haven't looked at Haste too much, I'll give it a try. My main problem is that I would like to find a solution that will continue working in years (somehow, that will became the solution for generating JS from Haskell code). That's why I see GHCJS (which just includes some patches to mainstream GHC) as the preferred solution, because it seems the most probable to continue working when new versions of GHC appear. 2013/9/4 Niklas Hambüchen m...@nh2.me Hi, I'm also interested in that. Have you already evaluated haste? It does not seem to have any of your cons, but maybe others. What I particularly miss from all solutions is the ability to simply call parts written in Haskell from Javascript, e.g. to write `fib` and then integrate it into an existing Javascript application (they are all more interested in doing the other direction). On Wed 04 Sep 2013 17:14:55 JST, Alejandro Serrano Mena wrote: Hi, I'm currently writing a tutorial on web applications using Haskell. I know the pros and cons of each server-side library (Yesod, Snap, Scotty, Warp, Happstack), but I'm looking for the right choice for client-side programming that converts Haskell to JavaScript. I've finally come to Fay vs. GHCJS, and would like your opinion on what's the best to tackle. My current list of pros and cons is: Fay === Pros: - Does not need GHC 7.8 - Easy FFI with JS - Has libraries for integration with Yesod and Snap Cons: - Only supports a subset of GHC (in particular, no type classes) GHCJS == Pros: - Supports full GHC - Easy FFI with JS - Highly opinionated point: will stay longer than Fay (but it's very important for not having a tutorial that is old in few months) Cons: - Needs GHC 7.8 (but provides a Vagrant image) ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Job opportunities at Galois
Hello, Are there any specific details to consider when applying? For example, is living in the US or having a visa required for application? Thanks in advance. 2013/6/27 Iavor Diatchki iavor.diatc...@gmail.com Hello, Galois is hiring! We're looking for researchers, principal investigators, and software engineers, including those with expertise in functional programming, formal methods, computer security, control systems, informatics, or networking. For more information, take a look at http://corp.galois.com/careers and please feel free to drop me an e-mail if you have questions. Cheers, -Iavor ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Teaching FP with Haskell
Maybe you could look at Helium [ http://www.cs.uu.nl/wiki/bin/view/Helium/WebHome]. From what I understand, it's a subset of Haskell specially designed for teaching. I heard that it provides also very good error messages and hints about typical errors. 2013/5/21 Rustom Mody rustompm...@gmail.com We are offering a MOOC on haskell : https://moocfellowship.org/submissions/the-dance-of-functional-programming-languaging-with-haskell-and-python Full Announcement on beginners list : http://www.haskell.org/pipermail/beginners/2013-May/012013.html One question that I have been grappling with in this regard: How to run ghc in lightweight/beginner mode? 2 examples of what I mean: 1. gofer used to come with an alternative standard prelude -- 'simple.pre' Using this, gofer would show many of the type-class based errors as simple (non-type-class based) errors. This was very useful for us teachers to help noobs start off without intimidating them. 2. Racket comes with a couple of levels. The easier numbers were not completely consistent with scheme semantics, but was gentle to beginners Any thoughts/inputs on this will be welcomed Rusi ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] list comprehension doesn't work
For a first sight, you cannot use x - [0..]*[0..] to mean 'all possible pairs x = a*b'. You would need to do something like [ (a*b, y) | a - [0..], b - [0..], a*b 5, a*b 500, and the rest of things ] 2013/5/14 John knowledge1...@gmail.com Hi, I have to write a function which returns a list of all pairs (x,y) where x, y ∈ N AND: – x is the product of two natural numbers (x = a · b, where a, b ∈ N) AND – x is really bigger than 5 but really smaller than 500, AND – y is a squer number (y = c² where c ∈ N) NOT greater than 1000, AND – x is a divisor of y. My attempt is as follows: listPairs :: [(Int, Int)] listPairs = [(x,y) | x-[0..], y-[0..], x-[0..]*[0..], x 5, x 500, (y*y) 1001, mod y x == 0] However it doesn't work unfortunatly Could anyone tell me where my mistake is? Thanks. -- View this message in context: http://haskell.1045720.n5.nabble.com/list-comprehension-doesn-t-work-tp5730158.html Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Contravariant applicatives, monads and arrows (was ANN: rematch, an library for composable assertions with human readable failure messages)
Hi, First of all, let me say that this work on matchers is really useful :) Following Roman advice, I'm trying to find a more principled approach that could be useful for this library. It seems that Match could easily be converted to Either and thus made into Functor, Applicative, Alternative and Monad. That would allow to write things like: User $ runMatch (isNot isEmpty) name * runMatch (hasItem (is '@')) email However, I'm also thinking about the correct way to combine matchers to get bigger matchers. Basically, if I have matchers on every field of a record, can I get a matcher for the entire one? My first idea was to make Matcher a functor. However, what I come was a contravariant functor: given (a - b) and Matcher b, I can easily construct a Matcher a by running the one in b over this function. So we have: contramap :: (a - b) - Matcher b - Matcher a My first question is: is there any structure similar to applicative functors or monads which work on these kind of contravariant functors? This also brought into my mind to see Matcher a just as functions a - Match and derive its properties from there. This may give better results that the above mentioned idea of looking it as a - Either String a, because in this latter case we have a in covariant and contravariant positions and it's difficult to get anything. On the other hand, it seems very easy, from a Matcher a and a Matcher b, to get a Matcher (a,b). This reminds me a bit about arrows, but without output parameters. Does it make sense? I've always been reluctant to arrows because I don't fully understand them, but maybe this is a good moment to learn. Do any of this make sense? I would really like to contribute to this great library! :) 2013/4/16 Tom Crayford tcrayf...@gmail.com: Roman, Thanks for the feedback! I'd originally left the QuickCheck and HUnit implementations in this library for convenience, thinking that there aren't going to be many people who care about the transitive dep. But you care, so I'm happy moving them out of core. I'll release a 0.2 with both the HUnit and the QuickCheck runners in separate libraries soonish. Thanks for the haddock tip and the implementation tips. Re the Control namespace, these matchers aren't exclusively a testing tool. I've been using the core api for other purposes as well (primarily for validating forms in user interfaces in conjunction with digestive-functors). I couldn't figure anything better to put it in apart from Control (I definitely don't want it in Test, even though that's going to be what most people use it for). I guess it could be in `Data`, but that doesn't sound much better to me. I'm not amazingly strong at building more principled interfaces right now, so I guess that's something I'll improve on. Are there any concrete suggestions you have there? I'd *like* these to have an `Alternative` instance, but making `Applicative`/`Functor` instances is beyond me right now (I guess I'd have to change the core API for that to work out). Tom ... ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Haskell / Functional Programmers Group in Madrid (Spain)?
Hi, Is there any Haskell or functional programmers user group in the region of Madrid? If not, I think it could be a great idea to get to know each other, and share experiences. Furthermore, we could try to organize some meetings with presentations, hackatons and so on (my personal ambition is to be able to organize another ekmett Workshop as the Japanese one - http://comonad.com/reader/2013/japanese-workshop-1/). I know there is some locations along Madrid dedicated to open source promotion, like http://madridonrails.com/, and which we could use for these meetings. I'm really looking forward to hearing from you! PS: Maybe a bare Haskell group is not big enough (at least according to Haskellers.com), but a functional programmers one may well be. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] [Announcement] HsLlvm v0.1: Using Hoopl to optimize LLVM Code
Hi, This seems a fantastic job! Do you have any plan to support LLVM - target phase, or do you know any project doing something similar? Thanks in advance. 2013/2/11 Ning Wang em...@ningwang.org Hi all, It is my dream for years to be able to manipulate LLVM in type safe language. I has explored the possibility of reimplementing LLVM in Haskell with Hoopl and made a small step to realize this dream. I am writing to announce the release of HsLlvm v0.1, which is a pure Haskell implementation (Not LLVM C++ binding) of LLVM. It is available through the link below. https://github.com/mlite/**HsLlvm https://github.com/mlite/HsLlvm Hightlight of this release: - Support LLVM 3.1 syntax - LLVM normalization - Dominator, mem2reg, DCE passes Project goals: - port all LLVM optimizations - provide functionalities to generate and manipulate LLVM code. Since LLVM is a complex IR and there are many sophisticated optimizations, this job won't be easy. Your contribution would be of value to eventually achieve this goal. Cheers, Ning __**_ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/**mailman/listinfo/haskell-cafehttp://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] How to take a minimum sub list that only contain certain number of elements of certain type?
It also comes to my mind that you can use something similar to regular expressions and parsing, seeing your list as a word made of Int elements. I think you can achieve it using Parsec or attoparsec. One you define your basic combinators for 'odd', you can see your sublist as the minimal part of the list matching (even* odd)(even* odd)(even* odd)(even* odd) 2012/9/25 Ivan Lazar Miljenovic ivan.miljeno...@gmail.com On 25 September 2012 16:51, Magicloud Magiclouds magicloud.magiclo...@gmail.com wrote: Hi, For example, I have an array [0..]. Now I want to take a sub list that starts from index 0, and only contain 4 odds, and is minimum result. The answer should be [0, 1, 2, 3, 4, 5, 6, 7]. If you have listTest :: [a] - Bool, then head . dropWhile (not . listTest) . inits ? How to do that? Combining lazy computing, I cannot figure out an efficient algorithm. -- 竹密岂妨流水过 山高哪阻野云飞 And for G+, please use magiclouds#gmail.com. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe -- Ivan Lazar Miljenovic ivan.miljeno...@gmail.com http://IvanMiljenovic.wordpress.com ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] specifying using type class
I don't know whether this is really applicable but: isn't emptyStack in
Ertugrul last message some kind of constructor? You can add any kind of
special constructors as functions in the type class which return a new
queue. For example:
class Stack s where
newEmptyStack :: s a
newSingletonStack :: a - s a
...
Why doesn't this fulfill you needs of specifying ways to construct new
elements?
2012/7/23 Patrick Browne patrick.bro...@dit.ie
On 22/07/12, *Ertugrul Söylemez * e...@ertes.de wrote:
You are probably confusing the type class system with something from
OOP. A type class captures a pattern in the way a type is used. The
corresponding concrete representation of that pattern is then written in
the instance definition:
No really. I am investigating the strengths and weaknesses of type classes
as a *unit of specification*.
I am aware that their primarily intended to act as interface description,
which I suppose is a form of specification.
To what degree could the QUEUE_SPEC (repeated below) from my first posting
be expressed as a type class?
From the feedback, I get the impression that an abstract specification
such as QUEUE_SPEC cannot be expressed as a type class (as an instance yes).
The stumbling block seems to be the abstract representation of
constructors.
In [1] the classes Moveable and Named are combined, but again each of
these classes are pure signatures.
Regards,
Pat
[1]Haskell: The Craft of Functional Programming (Second Edition) Simon
Thompson, page 270
module QUEUE_SPEC where
data Queue e = New | Insert (Queue e) e deriving Show
isEmpty :: Queue e - Bool
isEmpty New = True
isEmpty (Insert q e) = False
first :: Queue e - e
first (Insert q e) = if (isEmpty q) then e else (first q)
rest :: Queue e - Queue e
rest (Insert q e ) = if (isEmpty q) then New else (Insert (rest q) e)
size :: Queue e - Int
size New = 0
size (Insert q e) = succ (size q)
{-
some tests of above code
size (Insert (Insert (Insert New 5) 6) 3)
rest (Insert (Insert (Insert New 5) 6) 3)
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Re: [Haskell-cafe] specifying using type class
I think you are confusing ADTs, type classes and default declarations in
type classes. In Haskell, values are truly created only via abstract data
types. That would be a specific instance of your class:
data Stack a = Empty | Top a (Stack a)
Then you can write the implementation with respect to this concrete example.
What I was proposing, if you only need constructs, is that instead of
thinking of constructors, you may think of a factory pattern, similar to
that pattern in OOP: a function that creates the element for you. That
would be the newStack in your type class: every instance of a Stack must
provide a way to create new objects. However, this is just a function, so
you cannot pattern match there.
What type classes do allow you to do is to provide default implementations
of some function in you type class. But this must be a complete
implementation (I mean, executable code), not merely a specification of
some properties. For example, say you have functions in your class for
testing emptiness and poping elements. Then you may write a default
implementation of length:
class Stack s a | s - a where
isEmpty :: s a - Bool
pop :: s a - (a, s a) -- Returns the top element and the rest of the
stack
length :: s a - Int
length stack = if isEmpty stack then 0 else (length (snd (pop stack))) + 1
However, I think that what you are trying to do is to encode some
properties of data types into the type system. This is better done using
dependent typing, which in a very broad sense allows you to use value
functions into types. For example, you may encode the number of elements of
a stack in its type (so the type would be Stack ElementType
NumberOfElements) and then you may only pop when the Stack is not empty,
which could be encoded as
pop :: Stack a (n + 1) - (a, Stack a n)
Haskell allows this way of encoding properties up to some extent (in
particular, this example with numbers could be programmed in Haskell), but
for the full power (and in my opinion, for a clearer view of what's
happening) I recommend you to look at Idris (http://idris-lang.org/) or
Agda2 (http://wiki.portal.chalmers.se/agda/pmwiki.php). A very good
tutorial for the first is
http://www.cs.st-andrews.ac.uk/~eb/writings/idris-tutorial.pdf
Hope this helps!
2012/7/23 Patrick Browne patrick.bro...@dit.ie
Yes. I tried that, but due to my lack of Haskell expertise I cannot write
the constructor insertC1 below:
class QUEUE_SPEC_CLASS1 q where
newC1 :: q a
isEmptyC1 :: q a - Bool
insertC1 :: q a - a - q a
sizeC1:: q a - Int
restC1:: q a - q a
-- I do not know how to specify constructor insertC1 ?? = ??
insertC1 newC1 a = newC1
isEmptyC1 newC1 = True
-- isEmpty (insertC1 newC1 a) = False
On 23/07/12, *Alejandro Serrano Mena * trup...@gmail.com wrote:
I don't know whether this is really applicable but: isn't emptyStack in
Ertugrul last message some kind of constructor? You can add any kind of
special constructors as functions in the type class which return a new
queue. For example:
class Stack s where
newEmptyStack :: s a
newSingletonStack :: a - s a
...
Why doesn't this fulfill you needs of specifying ways to construct new
elements?
2012/7/23 Patrick Browne patrick.bro...@dit.ie patrick.bro...@dit.ie
On 22/07/12, *Ertugrul Söylemez * e...@ertes.de e...@ertes.de wrote:
You are probably confusing the type class system with something from
OOP. A type class captures a pattern in the way a type is used. The
corresponding concrete representation of that pattern is then written in
the instance definition:
No really. I am investigating the strengths and weaknesses of type
classes as a *unit of specification*.
I am aware that their primarily intended to act as interface description,
which I suppose is a form of specification.
To what degree could the QUEUE_SPEC (repeated below) from my first
posting be expressed as a type class?
From the feedback, I get the impression that an abstract specification
such as QUEUE_SPEC cannot be expressed as a type class (as an instance yes).
The stumbling block seems to be the abstract representation of
constructors.
In [1] the classes Moveable and Named are combined, but again each of
these classes are pure signatures.
Regards,
Pat
[1]Haskell: The Craft of Functional Programming (Second Edition) Simon
Thompson, page 270
module QUEUE_SPEC where
data Queue e = New | Insert (Queue e) e deriving Show
isEmpty :: Queue e - Bool
isEmpty New = True
isEmpty (Insert q e) = False
first :: Queue e - e
first (Insert q e) = if (isEmpty q) then e else (first q)
rest :: Queue e - Queue e
rest (Insert q e ) = if (isEmpty q) then New else (Insert (rest q) e)
size :: Queue e - Int
size New = 0
size (Insert q e) = succ (size q)
{-
some tests of above code
size (Insert (Insert (Insert New 5) 6) 3)
rest (Insert (Insert (Insert New 5) 6) 3)
Tá an teachtaireacht seo scanta ó thaobh ábhar agus
Re: [Haskell-cafe] Summer of Code idea: Haskell Web Toolkit
That sound like a really cool project. Where could I get more information about what could I do? You mention about contacting but I think it's better to keep the discussion open for everybody. Alejandro 2012/3/11 Jurriën Stutterheim j.stutterh...@me.com While I might be a bit biased (I spent a good deal of time working on improving the UHC JS backend), I think there are a lot of opportunities to get Haskell as a client-side language via the UHC, as Heinrich suggested. Alessandro Vermeulen recently wrote an entire front-end application using the UHC JS backend, so we know that it's capable of producing working front-end applications. See also[1]. Currently, however, it is still a bit of a pain to compile larger UHC JS projects, since Cabal support for UHC's different backends is limited. This could be one potential goal for your GSoC project: make it possible to type `cabal configure cabal build` and find a complete JS application in your dist folder. This would go a long way to make the UHC JS backend more usable and as a result, make Haskell a practical language to use for client-side programming. In solving this problem, you will have to think about how to deal with external Haskell libraries (UHC compiles JS from its internal core representation, so storing pre-compiled object files won't work in this case) and perhaps external JS libraries as well. You would also need to modify Cabal so that it becomes possible to select a specific UHC backend in your cabal files. Ideally, you will only need one cabal file for an entire web application; for both the front-end and backend. I think this would make a nice GSoC project. The scope of the above should be about right, but if you would be done way ahead of time, there are plenty of relevant related things you could work on (e.g., a UHC JS-specific Haskell Platform-like package). If this sounds interesting to you, let me know and I can send you some more detailed information about the UHC JS backend. As for mentoring, I might be able to help out there, but since the above project would revolve more around Cabal and not so much around the UHC internals, there might be more suitable mentors out there. Jurriën [1] http://uu-computerscience.github.com/uhc-js/ On 8 Mar 2012, at 14:58, Heinrich Apfelmus wrote: Chris Smith wrote: My first impression on this is that it seems a little vague, but possibly promising. My impression is also that this project proposal is rather vague. The general goal Haskell as client-side language for websites is clear and worthwhile, but I can't tell from the proposal whether the project will succeed or not, or, more importantly, *what* it will succeed at. The way I see it is that a successful GSoC proposal has to embody four key points: 1. One specific goal - I want to compile Haskell to JS via UHC's backend 2. in a larger context - as a step towards Haskell as a client-side language for websites. 3. that is accompanied by a successful example - To demonstrate that this works, I will write a small Asteroids game with HTML5 and Haskell 4. and that others can build upon - Moreover, I want to make it really easy for others to use the Haskell-JS compilation from cabal. The last point is extremely important: you don't want to build a hobbled prototype that languishes in a dark corner of github, you want to build a great software that changes the world by solving an important problem and making this solution really easy to use! Alejandro, your proposal mentions several different specific goals, each of which can be the basis for a successful GSoC project: * Make UHC's Haskell-JS compilation easy to use. * Design combinators for DOM manipulation in functional style, f.i. zippers. Note that this goal does *not* involve running Haskell on the client-side, the focus is solely on the design of combinators. This means that you'd have to use another example, for instance XML parsing. Of course, the idea is that this can be reused when someone else manages to run Haskell on the client. * Design combinators for remote procedure calling via HTTP/AJAX. Again, there is no Haskell running in the browser, the showcase would be two Haskell processes that communicate with each other via HTTP/AJAX. Each of these goals is a tangible improvement on the status quo and specific enough to be completed in a single GSoC project. Of course, the one specific goal is not supposed to be a limit, it is meant to be a foundation. If there is time remaining, the student is free to work on whatever he dreams of. By all means, don't hesitate to reach for the sky, but help us climb to the tree top first. Best regards, Heinrich Apfelmus -- http://apfelmus.nfshost.com ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Summer of Code idea: Haskell Web Toolkit
I agree with you that maybe this proposal is vague for a GSoC, but I don't think that websockets is a good option either, because not all browsers support them. Indeed, web development has gone a long way without contant communication with the server and I think Haskell should support this way of working too. My idea would rather go on the direction of using stablished Haskell concepts to web development. Some ideas are: - use an applicative interface like the one of Yesod for forms validation and sending - see the DOM via a Zipper interface, so widgets will anchor themselves in some point of the tree and change things around them - use FRP for Canvas interaction - ... Actually, thinking which Haskell concepts could behave well with client-side development is an interesting discussion by its own :) 2012/3/7 Greg Weber g...@gregweber.info This is obviously a great concept. However, it may not be appropriate for a GSoC. The design space is far too open, and it is not clear if anything in that space will end up beating plain old javascript. I think my proposal for an awesome websockets library [1] shows that this is putting the cart before the horse. For some of the potential javascript solutions, websockets is a dependency anyways. Without being able to hold open a connection to the server, required server interaction will be too slow. Yesod has been successful by explicitly avoiding any new radical paradigms, but by instead just trying to get the basics of web development established correctly. Without websockets, we don't have the basics down for fluid client-side interaction. The groundwork for this ticket has been laid: it should be easy to accomplish with time left over. So we are guaranteed a clear win for the community. With the time left over, a solution to the javascript problem can be attempted. But there is no burden for it to be solved within the summer. Next year the landscape will be more mature and we can try to come up with a solid proposal for the javscript problem if the community hasn't already created a solution. [1] http://hackage.haskell.org/trac/summer-of-code/ticket/1607 ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Summer of Code idea: Haskell Web Toolkit
Hi, I'm really looking forward to helping in the Summer of Code, if Haskell goes into it this year (something I take for granted :). I would like to propose an idea for a project, and I'm looking for suggestions about whether it's good, should be improved or it's just unfeasible. My idea is to make a client-side Haskell Web Toolkit, in the spirit of Google Web Toolkit, which would allow to program in Haskell the client part of a web application, and would complement the web frameworks already existing for Haskell (such as Yesod and Snap). The point is coming about with a Haskell-ish way to program applications, to reuse all the existing knowledge for our beloved language. I've added more details in a pre-proposal in Google Docs, available in https://docs.google.com/document/d/1FnTNO9uTobDHRTDXWurKns7vGTjeauw0nRhbtt6vavs/edit Tell me if you prefer to see it in other format, but I didn't want to generate a bigger e-mail. Thanks in advance. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Summer of Code idea: Haskell Web Toolkit
My idea would be reusing some of the already-available tools for compiling Haskell to JS (for example, UHC), and develop with any of them a complete library for client-side scripting; rather that redevelop a way to compile Haskell to JS. I think it's really a pity not being able to use things like what Yesod provides in a client-side context. And both sides would benefit: they can share common code for datatypes (as it's done in Google Web Toolkit), and autogenerate some code for sending or receiving AJAX requests, for example. 2012/3/6 Michael Snoyman mich...@snoyman.com On Tue, Mar 6, 2012 at 11:40 PM, Alejandro Serrano Mena trup...@gmail.com wrote: Hi, I'm really looking forward to helping in the Summer of Code, if Haskell goes into it this year (something I take for granted :). I would like to propose an idea for a project, and I'm looking for suggestions about whether it's good, should be improved or it's just unfeasible. My idea is to make a client-side Haskell Web Toolkit, in the spirit of Google Web Toolkit, which would allow to program in Haskell the client part of a web application, and would complement the web frameworks already existing for Haskell (such as Yesod and Snap). The point is coming about with a Haskell-ish way to program applications, to reuse all the existing knowledge for our beloved language. I've added more details in a pre-proposal in Google Docs, available in https://docs.google.com/document/d/1FnTNO9uTobDHRTDXWurKns7vGTjeauw0nRhbtt6vavs/edit Tell me if you prefer to see it in other format, but I didn't want to generate a bigger e-mail. Thanks in advance. I definitely think the idea has merit. In general I'm wary of solutions which try to compile down to Javascript[1], and I'm not sure if actually providing a full Haskell-to-JS approach is a good idea. Another possibility might be a DSL/combinator library for generating JS. Though at this point, I wouldn't rule out either approach. Yesod is currently wrapping up its 1.0 release (almost certainly out-the-door by the end of April), and after that our main focus is intended to be client-side integration, so we would certainly be happy to discuss design ideas and collaborate in general. Michael [1] I say compile down to to mean nontrivial changes, as opposed to something like Coffeescript, which is a fairly simple conversion. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] [haskell-cafe] Some reflections on Haskell
Hi, 2012/2/14 Doug McIlroy d...@cs.dartmouth.edu Kevin Jardine notices the full Haskell ecosystem ... is huge, and laments the absence of a sophisticated IDE to help manage it. Being a small-code type, I don't personally enjoy IDE's, which are undeniably useful in big projects, at the cost of a whole lot more to learn about programmering in addition to programming. There are now several IDEs (or development environments) that you may use for Haskell programming: I personally work on EclipseFP (so the environment is quite similar to Java), but there is also Leksah. I've seen people making incredible things using Emacs and the Haskell modes, so I think there is now quite nice support for Haskell programming. Apart from that, Haskell Platform and cabal makes it easy to use Haskell (at least as easy as PHP if you are using any of the LAMP packages in Windows, or Perl or Python). (Disclaimer: I'm currently one of the developers of EclipseFP) Nevertheless, I share Jardine's concern about the central problem. It is hard to find one's way in this ecosystem. It needn't be, as Java illustrates. To my mind Java's great contribution to the world is its library index--light years ahead of typical documentation one finds at haskell.org, which lacks the guiding hand of a flesh-and-blood librarian. In this matter, it seems, industrial curation can achieve clarity more easily than open source. I disagree with that. For me, one of the best things about Haskell community is Hackage, where I can actually find and browse package documentation in a centralized way. In these days, Maven or Ivy (for automatically resolving and getting Java dependencies) are seen as great tools for Java ecosystem, and in Haskell we have that, with an even easier way to add packages and new versions to the index! Indeed, I find that Hackage enables a workflow not available in any other programming language: say you don't find a feature in Hackage libraries. Well, you can be pretty sure that no one has programmed a library for your task (opposed to Java or .NET, where it may be a commercial library, and be found somewhere random in the internet). Once you program it, you can upload it to Hackage and share easily with the rest of the community. Finally, even though we may argue about the point that core Java libraries have better documentation that core Haskell libraries (although libraries such as container even give complexity bounds to their operations), I find better Haskell documentation for other different resources: see the free-available Learn you a Haskell, Real World Haskell (just to name some tutorials), the Snap and Yesod documentation (as opposed to the documentation of other web frameworks in the wild)... ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Module name space question
You can try the Haskell Browser in the Eclipse plug-in. 2011/12/12 wren ng thornton w...@freegeek.org On 12/12/11 9:32 AM, Ryan Newton wrote: I don't know why Hoogle didn't find one of the packages. I've often wondered about this related question: * Is there a place to browse the union of all namespaces in all hackage packages? There is, and it's awesome: http://folk.ntnu.no/hammar/**explore-hackage/http://folk.ntnu.no/hammar/explore-hackage/ Though it can be a bit slow to load, so try not to hammer the server too hard :) -- Live well, ~wren __**_ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/**mailman/listinfo/haskell-cafehttp://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Poll: Do you want a mascot?
Yes 2011/11/23 heathmatlock heathmatl...@gmail.com On Wed, Nov 23, 2011 at 1:40 PM, Alexander Bernauer alex-hask...@copton.net wrote: Yes PS: Why not using Doodle for the poll? Email is an easy way to make sure nobody votes twice. -- Heath Matlock +1 256 274 4225 ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] A Mascot
I really love the idea of Haskell having a mascot, and Da the Lamb seems a perfect one to me. 2011/11/22 heathmatlock heathmatl...@gmail.com I goofed on a few images, but I'm a bit tired to correct them at the moment. Also, I'll upload higher res images another time, they don't look terrible up close. On Tue, Nov 22, 2011 at 3:52 PM, heathmatlock heathmatl...@gmail.comwrote: Wasn't planning on it, but I saw some emails on the topic, so I worked on what I presented earlier: http://imgur.com/a/yIUOA A favicon is attached as well, it probably could use more work. -- Heath Matlock +1 256 274 4225 ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Fwd: problem with cabal install MissingH-1.1.1.0
There are for sure people who know better Haskell on Mac than me. When I made tests for EclipseFP, I just used the latest Haskell Platform release containing GHC 7.0.3 and it worked fine. Maybe the best thing you can do is start all over again using Haskell platform, if you don't need any new feature in GHC 7.2 Other option is compiling the development version of scion-class-browser (you can find it in https://github.com/serras/scion-class-browser) which drops the dependency on MissingH, and tell EclipseFP to use that version. 2011/9/23 Mariano Cortesi mcort...@gmail.com Hey! Thanks to all for the answers... i didn't know about ghc 7.2. I uninstalled ghc and reinstalled using homebrew (mac package manager). Now I have: The Glorious Glasgow Haskell Compilation System, version 7.0.4 cabal is: /usr/bin ➜ cabal --version cabal-install version 0.10.2 using version 1.10.2.0 of the Cabal library And now, I was able to install MissingH, but still can't make EclipseFP work correctly :S When i start EclipseFP, it tries to build the scion-browser, but it fails inmediately with a message from cabal: cabal: The program ghc version =6.4 is required but it could not be found. Google wasn't much help. Is anybody using EclipseFP? I've installed version 2.1 in eclipse indigo. I'm a regular eclipse user, but with haskell i'm lost. Best, Mariano * * ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] ANN: EclipseFP 2.1.0 released
Sorry, there was an error in the installation instructions. You need to download a version of Eclipse with Java support (Eclipse for Java developers, Eclipse for Java EE developers or Eclipse Classic). If you find any other error, you can report it in the mailing list at http://sourceforge.net/mailarchive/forum.php?forum_name=eclipsefp-develop 2011/9/3 Andreas Baldeau andr...@baldeau.net Hi there, I wanted to give the 2.1.0 version a try, so I followed the install instructions on the website and downloaded one of the available Eclipse packages (I chose Eclipse IDE for JavaScript Web Developers). Installing EclipseFP then gave me the following error: Cannot complete the install because one or more required items could not be found. Software currently installed: FP: Haskell support for Eclipse 2.1.0 (net.sf.eclipsefp.haskell.feature.group 2.1.0) Missing requirement: Haskell Plug-in Debug Core 2.1.0 (net.sf.eclipsefp.haskell.debug.core 2.1.0) requires 'bundle org.eclipse.jdt.junit 3.3.0' but it could not be found Cannot satisfy dependency: From: Haskell Plug-in Debug UI 2.1.0 (net.sf.eclipsefp.haskell.debug.ui 2.1.0) To: bundle net.sf.eclipsefp.haskell.debug.core 0.0.0 Cannot satisfy dependency: From: FP: Haskell support for Eclipse 2.1.0 (net.sf.eclipsefp.haskell.feature.group 2.1.0) To: net.sf.eclipsefp.haskell.debug.ui 2.0.3 As I couldn't find a hint where to report bugs, I thought I might simply reply to your announcement. Andreas ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Why the reluctance to introduce the Functor requirement on Monad?
I'll give my two cents about some design I've been thinking about. Instead of trying to derive all instances automatically, the programmer should explicitly tell them (so the problems about conflicting implementations would be minimised). I attach a piece of code of what I think could be done: instance Functor a = Monad a where -- notice the reversed = fmap = ... from Monad MyMonad derive Functor MyMonad With the from_derive_ clause, we are telling exactly from which = declaration to pull the definition from. The part of from should have already been written or derived, so we know exactly which instance the user is speaking about. More refinements to the syntax could be done, for example if we have: instance Functor a = Applicative a where fmap = .. instance Applicative a = Monad a where pure = ... (*) = ... Then, writing from Monad MyMonad derive Functor MyMonad would go through the entire tree of reverse instance declarations and create instances for Applicative, and from that a Functor one (of course, this should fail if we have more than one path, then the user should write the path explicitly as from Monad M derive Applicative M; from Applicative M derive Functor M). But it has the advantage of allowing later addition of classes in the path, that would be derived when recompiling the code that uses it. 2011/7/25 Ryan Ingram ryani.s...@gmail.com My guess is that nobody has put forward a clear enough design that solves all the problems. In particular, orphan instances are tricky. Here's an example: module Prelude where class (Functor m, Applicative m) = Monad m where return :: a - m a (=) :: m a - (a - m b) - m b () :: m a - m b - m b a b = a = const b pure = return (*) = ap fmap = liftM module X where data X a = ... module Y where instance Functor X where fmap = ... module Z where instance Monad X where return = ... (=) = ... -- default implementation of fmap brought in from Monad definition module Main where import X import Z foo :: X Int foo = ... bar :: X Int bar = fmap (+1) foo -- which implementation of fmap is used? The one from Y? -- ryan On Sun, Jul 24, 2011 at 8:55 PM, Ivan Lazar Miljenovic ivan.miljeno...@gmail.com wrote: On 25 July 2011 13:50, Sebastien Zany sebast...@chaoticresearch.com wrote: I was thinking the reverse. We can already give default implementations of class operations that can be overridden by giving them explicitly when we declare instances, so why shouldn't we be able to give default implementations of operations of more general classes, which could be overridden by a separate instance declaration for these? Then I could say something like a monad is also automatically a functor with fmap by default given by... and if I wanted to give a more efficient fmap for a particular monad I would just instantiate it as a functor explicitly. I believe this has been proposed before, but a major problem is that you cannot do such overriding. -- Ivan Lazar Miljenovic ivan.miljeno...@gmail.com IvanMiljenovic.wordpress.com ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Text.CSV questions
Maybe you can directly distinguish if the parser returned an error (Left) or not (Right), instead of using lefts and rights: import Text.CSV import Data.Either import System import Data.List main = do [inpFileName] - getArgs putStrLn (Parsing ++inpFileName++...) result - parseCSVFromFile inpFileName case result of Left error - do print Parse error: print error Right csv - print csvL putStrLn All done. 2011/6/17 Dmitri O.Kondratiev doko...@gmail.com On Fri, Jun 17, 2011 at 1:04 PM, Vincent Hanquez t...@snarc.org wrote: On 06/17/2011 10:00 AM, Dmitri O.Kondratiev wrote: Hi, I try to parse csv file with Text.CSV, like this: import Text.CSV import System main = do [inpFileName] - getArgs putStrLn (Parsing ++inpFileName++...) let result = parseCSVFromFile inpFileName print result === As a result I get: No instance for (Show (IO (Either Text.Parsec.Error.ParseError CSV))) arising from a use of `print' Possible fix: add an instance declaration for (Show (IO (Either Text.Parsec.Error.ParseError CSV))) === Question: How to add a Show instance for (IO (Either Text.Parsec.Error.ParseError CSV))) ? Hi Dmitri, you don't add a show instance for IO, but you unwrap the IO Monad first and then show the result. let result = parseCSVFromFile inpFileName should be: result - parseCSVFromFile inpFileName -- Vincent Thanks everybody! This is how I solved it: import Text.CSV import Data.Either import System import Data.List main = do [inpFileName] - getArgs putStrLn (Parsing ++inpFileName++...) result - parseCSVFromFile inpFileName let errors = lefts [result] let csvL = rights [result] print CSV list print csvL print Errors print errors putStrLn All done. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Problem with linker
No, it does not report any problem. 2011/6/4 Clint Moore cl...@ivy.io On Sat, Jun 04, 2011 at 01:17:03AM +0200, Alejandro Serrano Mena wrote: Hi, I'm trying to use Hoogle as a library in my Summer of Code project. But when I try to compile using Cabal, I get the following error: Linking dist/build/scion-browser/scion-browser ... /home/serras/.cabal/lib/hoogle-4.2.4/ghc-7.0.2/libHShoogle-4.2.4.a(Serialise.o): In function `s1ePR_info': (.text+0x2015): undefined reference to `hooglezm4zi2zi4_Pathszuhoogle_version1_closure' /home/serras/.cabal/lib/hoogle-4.2.4/ghc-7.0.2/libHShoogle-4.2.4.a(Serialise.o): In function `s1f8a_info': (.text+0x338f): undefined reference to `__stginit_hooglezm4zi2zi4_Pathszuhoogle_' I've been looking for some information and it seems to be related with the fact that Hoogle first builds a library and then build an executable using the library, but all files get recompiled in that second pass. Is there any way to workaround this problem? Does 'ghc-pkg check' report any problems? ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Problem with linker
I'm using the last Haskell Platform available in Arch Linux, with GHC 7.0.2 and Cabal 1.10.1.0 (the last one). The problem is not installing Hoogle, because it builds and works correctly, but linking with the library Hoogle provides. 2011/6/4 Rogan Creswick cresw...@gmail.com On Fri, Jun 3, 2011 at 4:17 PM, Alejandro Serrano Mena trup...@gmail.com wrote: I've been looking for some information and it seems to be related with the fact that Hoogle first builds a library and then build an executable using the library, but all files get recompiled in that second pass. Is there any way to workaround this problem? Upgrading Cabal / cabal-install is a good place to start, if you're not already using the 0.10's. I also suggest using cabal-dev, since issues like this can be caused by combinations of dependencies that conflict. There's a good chance that you just have a weird mix of compiled libraries that don't all work together, and cabal isn't able/willing to rebuild everything necessary to make all the things in your user package db work together. I very recently installed Hoogle locally, on a fresh system, so I'm fairly confident it's still possible without too many headaches :). --Rogan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Problem with linker
Hi, I'm trying to use Hoogle as a library in my Summer of Code project. But when I try to compile using Cabal, I get the following error: Linking dist/build/scion-browser/scion-browser ... /home/serras/.cabal/lib/hoogle-4.2.4/ghc-7.0.2/libHShoogle-4.2.4.a(Serialise.o): In function `s1ePR_info': (.text+0x2015): undefined reference to `hooglezm4zi2zi4_Pathszuhoogle_version1_closure' /home/serras/.cabal/lib/hoogle-4.2.4/ghc-7.0.2/libHShoogle-4.2.4.a(Serialise.o): In function `s1f8a_info': (.text+0x338f): undefined reference to `__stginit_hooglezm4zi2zi4_Pathszuhoogle_' I've been looking for some information and it seems to be related with the fact that Hoogle first builds a library and then build an executable using the library, but all files get recompiled in that second pass. Is there any way to workaround this problem? ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
