Re: [Haskell-cafe] haskore - lilypond - typesetting?
Here's one I did earlier... http://www.flickr.com/photos/44929957@N03/4459628487/lightbox/ This is Haskore implementation of Chick Corea's Child Song 6 rendered to LilyPond - I don't imagine Mr. Corea's publishers will be sending me a takedown request any time soon. There's a lot missing from Haskore that is needed to make good scores - the renderer of the above took a lot of effort with metrical grouping but the result is still abysmal. I doubt mathematics can help (common practice) music typesetting much - Western notation has had a thousand years to develop without the constraint of a regular syntax; so if Lilypond is horrible it is mostly the fault of what it tries to typeset (it does make some unwarranted mistakes like over-restricting the characters it can use for variable names and its parenthesizing is horrible). On 21 August 2013 14:05, Johannes Waldmann waldm...@imn.htwk-leipzig.dewrote: I tried using lilypond ( http://www.lilypond.org/ ) for typesetting of sheet music. While the output looks nice, the input language IMHO is quite horrible, because the underlying data/execution model is underspecified. For some parts, it tries to describe the logical structure of the score; but for others, the layout; and in addition it has several non-obvious context-dependencies (but see below), preventing modularity. Is there a better option? E.g., starting from a clear mathematical model, as in Haskore, and use lilypond only as a PDF rendering engine? Do I want hly / hts perhaps? http://rd.slavepianos.org/?t=hly As I see it, the main high-level design problem is that the source language needs partial evaluation annotations for abstractions applications: sometimes they should be expanded (for MIDI rendering, always) and sometimes not (in typesetting, to create repetition marks instead of actually repeating notes). PS: I agree that some of lilypond's context dependencies (relative pitch, implicit note length) do really save large amounts of tedious typing: c4 e g a c1 is much more economical than [c 1 qn, e 1 qn, g 1 qn , a 1 qn, c 2 fn] which I guess is the Haskore equivalent. ___ 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] Int is broken [Was: Different answers on different machines]
There was a quite long discussion here: http://conal.net/blog/posts/notions-of-purity-in-haskell On 2 June 2013 22:02, Tommy Thorn tt1...@yahoo.com wrote: ... I wish this fatal flaw would be reconsidered for the next major revision. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] [haskell.org Google Summer of Code 2013] Approved Projects
Similarly (to some degree), in the ML world John Reppy had a very nice system that employed user customization via combinators rather than inference to generate application/library specific FFIs, see: http://people.cs.uchicago.edu/~jhr/papers/2006/gpce-fig.pdf On 29 May 2013 18:57, Jason Dagit dag...@gmail.com wrote: Are you folks aware of the work on this topic by Tristan Ravitch? https://github.com/travitch/foreign-inference Jason ___ 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] Infrastructure for testing the impact of a Functor/Applicative/Monad hierarchy
Has anyone surveyed the in-print textbooks, tutorials, or tried to assess how much Haskell (H98, H2010, Glasgow Haskell?) is used in teaching? Having the wrong hierarchy is a minor annoyance to us members of the cognoscenti, but a change outside a revision of the language standard could leave a lot of beginners and the teaching material they rely on stranded. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Backward compatibility
Hi Adrian I don't want to argue against your rant for the sake of it, but Haskell is a fairly conservative language. The Glasgow Haskell Compiler supports it's own dialect Glasgow Haskell which is fast moving, but the developers of GHC do work hard to maintain compatibility with standard Haskell 98 and Haskell 2010 (optionally enabled with compiler flags). Afterall Haskell now is fairly widely used as a teaching language which befits stability as course textbooks, lecture plans etc. can't be in hock to a language that changes every year. Best wishes Stephen ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] partially applied data constructor and corresponding type
What you probably want are type level integers (naturals) Yury Sulsky used them in the message above - basically you can't use literal numbers 1,2,3,... etc as they are values of type Int (or Integer, etc...) instead you have to use type level numbers: data One data Two Work is ongoing for type level numbers in GHC and there are user libraries on Hackage so there is a lot of work to crib from. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Haskell compilation errors break the complexity encapsulation on DSLs
Helium - Utrecht University's simplified Haskell - had scriptable Type inference directives so the creator of an EDSL was able to augment the type checker to provide better error messages, see: Scripting the Type Inference Process Bastiaan Heeren Jurriaan Hage S. Doaitse Swierstra ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Contravariant applicatives, monads and arrows (was ANN: rematch, an library for composable assertions with human readable failure messages)
On 16 April 2013 16:12, Alejandro Serrano Mena trup...@gmail.com wrote: 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: Have you seen Ralf Hinze, Johan Jeuring and Andreas Loeh's paper on Contracts? The found their Contract datatype formed a comonad - at the time this seemed to be one of the few (non-synthetic) uses of comonads. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Prolog-style patterns
This is a recurring theme, see also here: http://www.haskell.org/pipermail/haskell-cafe/2009-May/061498.html On 8 April 2013 16:53, Tom Murphy amin...@gmail.com wrote: Also, for some history, this was discussed a while back: http://www.mail-archive.com/haskell@haskell.org/msg03721.html ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] graphical editor links ?
A while ago there was a framework Blobs for building box-connector diagram editors. It is probably a somewhat bit-rotted now: http://www.cs.york.ac.uk/fp/darcs/Blobs/ I seem to remember a Haskell Workshop report about Dazzle (the application that was the genesis of Blobs) but it doesn't appear to be linked from that page. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] install cuda
It looks like you are using Cygwin for a Unix-alike environment. For building Haskell bindings to C libraries you are better off with MinGW + MSYS. On 30 March 2013 19:43, Peter Caspers pcaspers1...@gmail.com wrote: I am trying to install the cuda package on a Windows 7 enviroment. However I run into an error and can not figure out, what it is. Can someone help ? ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Parser left recursion
More primitively, Parsec and its predecessor Hutton-Meijer provide the chainl/chainr combinators, these automatically remove left recursion within the parser - i.e. you don't have to rewrite the grammar. On 20 February 2013 08:19, Dmitry Olshansky olshansk...@gmail.com wrote: Did you see expression parser in parsec package? Is it not enough? ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] searching the attic for lambada
Hi John I have a copy of version 0.1 and a related PDF - I'll email you as attachments them offlist On 13 February 2013 14:16, John Lask jvl...@hotmail.com wrote: I'm interested in resurrecting the idl generator from lambada: http://www.dcs.gla.ac.uk/mail-www/haskell/msg02391.html is the code out there in anyone's attic? ___ 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] CoArbitrary
I think GAST - the Clean equivalent of Quickcheck - generates functions. There are certainly quite a few papers by members of the Clean team documenting how they generate them. On 9 February 2013 07:07, Tony Morris tonymor...@gmail.com wrote: [...] I hope I have phrased this in a way to make the point. I found it a bit difficult to articulate and I do wonder (hope!) that others encounter similar scenarios. Thanks for any tips! ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Parsec Vs. src exts
On 2 February 2013 20:08, Sean Cormican seancormic...@gmail.com wrote: Can anybody provide me with some guidance on whether to try and create the parser using Parsec or if haskell-src is a better option. In the case that haskell-src is a better option, are there any tutorials or documents that I would benefit from reading? As Roman Cheplyaka says, go with Haskell-src-exts... Haskell-src-exts parses real Haskell - including most (if not all?) GHC extensions. If you were wanting to analyze 'in the wild' Haskell projects you might also want to use CPPHS as many Haskell projects use the CPP preprocessor. Once you have chosen the appropriate parse function (I remember that haskell-src-exts provides quite a few) there is not much work to using haskell-src-exts. Writing your own parser with Parsec would be quite a lot of work. But it would it might be an advantage if you want, say, custom error reporting. Also, if your micro-Haskell is not actually a proper subset of Haskell, then you would have to write your own parser. The original distribution of Parsec (available from Dann Leijen's legacy page at the Utrecht University) has parsers for two small functional languages Mondrian and Henk that are syntactically quite close to Haskell. These are useful starting points if you choose the Parsec route. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Monadic parser vs. combinator parser
On 30 January 2013 12:38, Ertugrul Söylemez e...@ertes.de wrote: A monadic parser /is/ a combinator parser. The code you linked just doesn't go as far as wrapping it up with a newtype and providing a monad instance. Further, (+) in the linked example is monadic bind and `result` is `return`. The code looks more succinct than early Parser combinator libraries (like Hutton / Meijer) because it defines quite a few more combinators. Equivalents are available if you use say Parsec plus the usual applicative combinators. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] resources for learning Hindley-Milner type inference for undergraduate students
There is a summary paper by Sunil Kothari and James L. Cladwell covering the algorithms M, J and W with informal presentations plus code available in Ocaml. Paper is on Citeseer, code is available from Sunil Kothari's home page. Martin Grabmueller has a tutorial implementation of algorithm W in Haskell: http://www.grabmueller.de/martin/www/pub/pub.en.html On 18 January 2013 10:06, Petr P petr@gmail.com wrote: Dear Haskellers, could somebody recommend me study materials for learning Hindley-Milner type inference algorithm I could recommend to undergraduate students? ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Generating random arguments for a function
In general you can't do this whether you use pats of QuickCheck or not - `randomEvalute` would need to inspect the supplied function to see how many input parameters it has so it can list them, but there is no such introspection in Haskell. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Generating random arguments for a function
Yes - I was just checking the first QuickCheck paper to see how the authors did this. You would need a new type class that works like `Testable` and the versions of associated machinery `forAll` and `evaluate` to unroll function application. On 13 January 2013 09:28, Roman Cheplyaka r...@ro-che.info wrote: This can be done with relatively simple type class hackery. In fact, QuickCheck already does that in order to generate arguments and print them in case of failure. Roman ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Difference Lists versus Accumulators
See the first Worker / Wrapper paper by Andy Gill and Graham Hutton. Particularly there is exactly this derivation of reverse through preliminarily using a Hughes (difference) list. On 8 January 2013 12:22, Edsko de Vries edskodevr...@gmail.com wrote: Hey all, The connection between difference lists and accumulators is probably well known, but I only recently realized it myself and a quick Google search didn't find turn up any page where this was explicitly stated, so I thought this observation might be useful to some. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Navigating 'Strategic' programming babel
Strafunski is now rather out of date - it was developed before Cabal and used a custom install depending whether or not you wanted to use the DriFt preprocessor. Andy Gill has a modern re-implementation of Strafuski on Hackage called KURE. Aside from SYB, Neil Mitchell's Uniplate is popular and generally well documented. On 17 December 2012 11:12, Ravi Sahni ganeshsahn...@gmail.com wrote: However it seems that the strafunski-ecosystem being integrated with aterm etc, likewise stratego, are more suited to full-scale language processing. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Exploring Programming Language Theory
If you want compiling functional languages and can relax the requirement for up to date: Antoni Diller's Compiling Functional Languages is good. It is short enough (300 pages) that you could reasonably work through it and it includes the full source of a compiler in the appendix - written in Pascal so translating it to something else is a sufficient exercise. It is long out of print, but copies turn up on Amazon - I got it from Amazon UK for a couple of pounds. Also Franklyn Turbak and David Gifford's Design Concepts for Programming Languages is very good (and new!) but huge. It is not quite exhaustive - as a skim reader I wanted the specification / translation rules for a particular compile step and frustratingly it was left as an exercise. Otherwise it is a very good presentation - it uses translation rules (ala the LaTeX Semantic package) rather than source code throughout, so once you are used to the style it is both very concise (and precise) and unlikely to go out of date any time soon. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Design of a DSL in Haskell
In Haskell, shallow DSLs generate values - deep DSLs generate structures (typically abstract syntax trees), the structure can subsequently be used to generate a value (or a C program, or a HTML page, etc.). See Andy Gill and colleagues Types and Type Families for Hardware Simulation and Synthesis, The Internals and Externals of Kansas Lava for a fuller definition. http://www.ittc.ku.edu/csdl/fpg/sites/default/files/Gill-10-TypesKansasLava.pdf Other communities may have their own definitions. On 4 December 2012 10:01, Kim-Ee Yeoh k...@atamo.com wrote: On Tue, Dec 4, 2012 at 4:53 PM, Joerg Fritsch frit...@joerg.cc wrote: is a shallow embedded DSL == an internal DSL and a deeply embedded DSL == an external DSL or the other way around? Roughly speaking, yes. But a deep DSL doesn't mean you've got to have a parser tokenizer IO input. You can get a deep DSL merely from the free monad construction. -- Kim-Ee ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Is there any movement/need in new 'base' package and co?
Haskell 2010 avoided library revisions - 12 years had elapsed since the last language definition and updating the language was deemed the priority. There have been suggestions on the Libraries list that the next major language revision should also look at the core libraries. On 2 December 2012 18:59, Евгений Пермяков permea...@gmail.com wrote: So, the questions arise: - When problems will ruin the language? - When and which actions are needed to avoid this? - If major rewrite will be initiated, what problems it should target? - And how to make the transition easier? ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] To my boss: The code is cool, but it is about 100 times slower than the old one...
On 29 November 2012 18:09, Fixie Fixie fixie.fi...@rocketmail.com wrote: What is your experience, dear haskellers? To me it seems this beautiful language is useless without a better lazy/eager-analyzer. Since when has speed been the sole arbiter of utility? 10 years ago I switched from Clean to Haskell, even though Clean was then faster (and included a good strictness analyser). The available libraries for Haskell is what swung the decision for me. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] OpenAL - compiling problem
Hi Gary Which version of GHC are you using? My suspicion is that ALCdevice might be a newtype falling foul of recent changes to GHC... v7.4.1: GHC now requires, as per the standard, that if a newtype is used in an FFI declaration, then the constructor for that type must be in scope. For now you only get a warning if it is not, but in the future this will be an error. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] OpenAL - compiling problem
I think OpenAL is now unmaintained. You could try to find AndrewMiller who updated the last version, otherwise you might have to patch it yourself or ask a developer of a dependent package if they would consider pushing another unmaintained release to Hackage. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Instead of Haskell running on the JVM is there a way for Haskell to call a JVM language ...
There has been, as Antony Courtney was using Java2D for vector graphics called from Haskell in his Haven system. The FFI was GCJNI (Green Card JNI) - I'm not sure where it exists now or how much it has bit rotted. On 20 November 2012 05:36, KC kc1...@gmail.com wrote: Instead of Haskell running on the JVM is there a way for Haskell to call a JVM language (or generate bytecode) to access the Java class libraries when needed? ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Parsing different types, same typeclass
With existentials an extesible version might look like this:
{-# LANGUAGE ExistentialQuantification #-}
{-# LANGUAGE ScopedTypeVariables #-}
... class Action and datatypes A and B the same as before ...
-- some new ones...
data C = C Int
deriving (Read, Show)
instance Action C where
run (C n) = n
data D = D Int
deriving (Read, Show)
instance Action D where
run (D n) = n
The important one:
data PolyA = forall a. Action a = PolyA a
parseAction :: String - PolyA
parseAction str
| (A `isPrefixOf` str = PolyA $ (read :: String - A) str
| (B `isPrefixOf` str = PolyA $ (read :: String - B) str
-- can add new cases
| (C `isPrefixOf` str = PolyA $ (read :: String - C) str
| (D `isPrefixOf` str = PolyA $ (read :: String - D) str
This is extensible to some degree as you can add new cases of
different types, but all you can do with these different types is
run them to make an Int, so it is equivalent to the second version I
gave previously:
parseAction :: String - Int
parseAction str
| (A `isPrefixOf` str = run $ (read str :: A)
| (B `isPrefixOf` str = run $ (read str :: B)
| (C `isPrefixOf` str = run $ (read str :: C)
| (D `isPrefixOf` str = run $ (read str :: D)
i.e instead of using an existential type to hold something polymorphic
that can be run to produce an Int, just call run at the point of use
making an Int.
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Re: [Haskell-cafe] Parsing different types, same typeclass
Being concrete, all you can do is: parseAction :: String - Either A B parseAction str | (A `isPrefixOf` str = Left $ read str | (B `isPrefixOf` str = Right $ read str parseAction :: String - Int parseAction str | (A `isPrefixOf` str = run $ (read str :: A) | (B `isPrefixOf` str = run $ (read str :: B) As you can't return a polymorphic /a/ when you have typed the cases to A or B. Being less concrete, no doubt you can use existentials, but at this point I'd recommend you re-evaluate what you are trying to do. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] curl package broken in Windows
Isn't Curl a C library (with a Haskell binding)? For Haskell bindings the best environment on Windows is usually MinGW / MSys, but your error suggests you should be building from Cygwin in this case. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] curl package broken in Windows
I've just checked Hackage - the Curl package (haskell) is a binding to libcurl (c library). It looks like MinGW / MSys is the best option - there are some notes are written by Sigbjorn Finne (who wrote the Haskell binding) although they are now quite old: http://haskell.forkio.com/Home/curl-win32 It looks like Sigbjorn, was cross compiling a MinGW build for libcurl from Cygwin, instead I'd build under a proper installation of MinGW / MSys. The bits of MinGW that are distributed with GHC aren't sufficient for this - you will need a proper installing of MinGW / MSys. On 9 November 2012 20:13, Stephen Tetley stephen.tet...@gmail.com wrote: Isn't Curl a C library (with a Haskell binding)? ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Partial application in case expression rules
There's a Glasgow extension that gets you to this:
treeFold :: (a - a - a) - Tree a - a
treeFold f = \case
Leaf {} - id
Node {} - f `on` treeFold f
Or maybe this if parens are needed:
treeFold :: (a - a - a) - Tree a - a
treeFold f = \case
(Leaf {}) - id
(Node {}) - f `on` treeFold f
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Re: [Haskell-cafe] Segment Tree based Set
Are Martin Erwig's diets anything close? http://web.engr.oregonstate.edu/~erwig/diet/ On 29 October 2012 04:48, Tony Morris tonymor...@gmail.com wrote: Hi, I was wondering if anyone knows of a package implementing a fast lookup for an element in ranges. For example, this operation: Ord a = a - [(a, a)] - Bool ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] serialize an unknown type
Hi Corentin It looks like you are writing the event handler on the server side. If so, the range of events you can handle is fixed to just those you implement handlers for - having an openly extensible event type is useless if this is the case. Ignoring client/server for a moment, a function (State - State) would be the most extensible API you could allow for clients. You don't need to worry about an open set of Event types, a client knows the state exactly and doesn't need extensibility. Client/Server operation won't allow a state transformer API as Haskell can't readily serialize functions. But you can implement a command language enumerating state changing operations. The second Quickcheck paper gives a very good example of how to implement such a command language. Testing Monadic Code with QuickCheck (2002) Koen Claessen , John Hughes www.cse.chalmers.se/~rjmh/Papers/QuickCheckST.ps Or Citeseer if you need a PDF: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.19.9275 ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Which advanced Haskell topics interest you
On 4 October 2012 18:04, Kim-Ee Yeoh k...@atamo.com wrote: Something to consider is that it's not so much whether the material is basic, advanced, or intermediate; it's that the way it's being presented is boring and ineffective. I'd suggest there is enough range in the Haskell books now available, that for most tastes, there's a beginners to intermediate book already a given learner wouldn't consider boring. Of course different learners will like different ones... As for an advanced book, maybe limiting the subject to one domain (concurrency / DSLs for graphics / pick a favourite ...) might make a better book than one targeting a mix of advanced topics. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] type variable in class instance
Whilst dynamic typing isn't idiomatic for Haskell, it seems like you've decided you want it. So why not use Data.Dynamic rather than roll you're own dynamic typing with Typeable? ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Best way to build a GHC backend?
On 9 July 2012 15:38, Brent Yorgey byor...@seas.upenn.edu wrote: I should point out that the ball already IS rolling -- ranging from EDSLs that compile to JavaScript [1,2] to macro systems [3] to more serious full-featured efforts [4,5]. Also, a JavaScript backend has recently been developed for Clean, the other major lazy functional language. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Origin of Delimited Continuation Operators
You could try working back from the references in Dorai Sitaram's Handling Control 1993, which is an important paper in the Scheme community covering this area. http://www.cs.rice.edu/CS/PLT/Publications/Scheme/pldi93-s.ps.gz Shift for instance is referenced back to at least Davy and Filinski's Abstracting Control 1990. On 25 June 2012 03:13, aditya siram aditya.si...@gmail.com wrote: Hi all, I working through a few papers and Oleg's delimited continuation implementation and I'm wondering how the operators (shift, shift0P, control, reset, etc) got their name. -deech ___ 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] Origin of Delimited Continuation Operators
On 25 June 2012 18:02, Stephen Tetley stephen.tet...@gmail.com wrote: Shift for instance is referenced back to at least Davy and Filinski's Abstracting Control 1990. Typo - Olivier _Danvy_ not Davy ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Martin Odersky on What's wrong with Monads
False! You only have to change the parts of the program that need the effect that the monad provides. A well designed program will likely have much of its code in pure libraries. Think of the monadic code as a scripting language that you bind your libraries together with to make the program. On 24 June 2012 06:31, Jonathan Geddes geddes.jonat...@gmail.com wrote: Cafe, [SNIP] What's wrong with Monads is that if you go into a Monad you have to change your whole syntax from scratch. Every single line of your program changes if you get it in or out of a Monad. [SNIP] Thoughts? ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Haskell is rapidly approaching the top 20
Ah, enjoy it while it lasts. In April, Kuzcek PLT Institut, Kazakhstan [*] and the Club of Rome declared 2012 as the year of Peak FP. It's downhill from here on… [*] aka @plt_borat on Twitter - whose views are probably no more unreliable than Tiobe. On 16 June 2012 22:58, Henk-Jan van Tuyl hjgt...@chello.nl wrote: -✂ TIOBE [snip] [Snip] what language could become the next big new programming language. We suggested several candidates such as Scala, Erlang and Clojure. Clearly, the new thing was expected to come from the functional programming field. ... ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Finding the average in constant space
There are a few blog posts by Conal Elliott and Max Rabkin (I think) reifying folds as a data type to get more composition and thus fold different functions at the same time. Search for beautiful folding with the above authors names. Personally I didn't find the examples significantly more beautiful that using regular composition in a normal fold - only that that the helper functions to manage pairs aren't in the standard library. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Building pattern and trying monads
It's common to use a writer monad possibly stacked with other monads (e.g. a state monad for fresh variable names) for code generation that approximates macro expansion - i.e. one call in Haskell maps to one-or-more lines of code in the output language, no global transformations are permitted. If you want transformations, then it is likely you will need to model the syntax of the output language or an intermediate language to have something concrete to transform. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Can Haskell outperform C++?
On 21 May 2012 17:27, Yves Parès yves.pa...@gmail.com wrote: I fail to see how the GUI part would suffer from lack of performance if the rest of the system is fine. I would hate to be bold, but to me this case sounds a little bit like MVC done wrong if the breaking GUI apart from the rest of the software is really that impossible. A few years ago one of the architects at Adobe published some slides on the software engineering aspects of PhotoShop, unfortunately I couldn't find them on the web when I tried recently but I believe it stated the codebase was well over 1 million lines of C++ and the GUI (including Adobe's own frameworks) accounted for more than half of that... GUI's often *are* the program rather than a way in to use it. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] darcs patch dependencies in dot format
On 16 May 2012 19:43, wren ng thornton w...@freegeek.org wrote: You should probably farm out the toDot rendering to one of the libraries that focuses on that[1], since they'll have focused on the efficiency issues--- or if they haven't, then you can contribute improvements there, helping everyone win. In particular, you're using Strings which is a notorious performance sink. Using Text or ByteStrings would be far better. I'm not sure swapping to Text or ByteStrings make be much great shakes for this. If you are generating huge files, where it would count - then the files are going to be a real problem for Graphviz to render (unless Graphviz has seen some optimization recently...). That said, I would recommend Sönke uses a pretty print library rather than Printf as using the former makes for much more idiomatic for Haskell and generally performs well enough for generational activities even if it uses Strings internally. Best wishes Stephen ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Data-Type Serialization
I think both ATerms and the Zephyr project's ASDL could handle recursive types - certainly ASDL was a sum and product representation like ML or Haskell's algebraic types (ATerms were a bit more like Prolog). Both never gained much traction and for better or worse JSON won the game. I implemented generators for both a very long time ago when I was staring out with Haskell. I didn't use TH or a generics library. If I were doing it again now I'd start with a generics library and see how that pans out - basically you want a type representation and generics libraries have that already. Also I'm no fan of TH. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] prettyprint with IO
Haskell-src-exts has had a monadic wrapper over HughesPJ for a long time. It is just a Reader (not a transformer) so it can handle user supplied spacing widths, etc. On 13 April 2012 06:02, Warren Harris warrensomeb...@gmail.com wrote: Thanks for the suggestions. No sooner did I send my message than I came to the same conclusion of creating a monadic version of the combinators to simplify the migration. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Mixing Unboxed Mutable Vectors and Parsers
Hi Myles It seems odd to mix parsing (consuming input) with mutation. What problem are you trying to solve and are you sure you can't get better phase separation than this paragraph suggests? My first idea was to simply parse all the deltas, and later apply them to the input list. However, I can't do that because the value of the deltas depend on the value they're modifying. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Mixing Unboxed Mutable Vectors and Parsers
On 8 April 2012 19:17, Myles C. Maxfield myles.maxfi...@gmail.com wrote: It's a JPEG parser. Ahem, I'm a bit of of my depth then, but one thing you should consider is that writing your own parser monad is trivial, especially for well defined binary formats. Well defined binary formats should be deterministic and don't need backtracking, hence you won't need to worry about defining Alternative / MonadPlus instances which is where the complication lies. As you should be able to live without backtracking for JPEG it shouldn't be hard to make the parser efficient if you stick closely to the API of the Vector or Array library you are using - e.g. you might want to move a cursor forward through the Array rather than unconsing [*] at the head which would create work for the garbage collector. This should still be amenable to streaming - you just work at a larger chunk size. Presumably you've seen Jeroen Fokker's paper on JPEG decoding with Gofer? (Gofer is ~= Haskell). [*] Parsec etc. work by unconsing the head of the input stream. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Fail-back monad
There is also recent work by Aaron Turon and Olin Shivers - Modular Rollback through Control Logging http://www.ccs.neu.edu/home/shivers/ http://www.ccs.neu.edu/home/turon/ Note that as well as the paper on Olin Shivers's site there is a more recent monadic presentation on Aaron Turon's site with Conor McBride... On 28 March 2012 18:11, Stephen Tetley stephen.tet...@gmail.com wrote: Maybe this is a version of William Harrison's DebugT monad with rollback, listed in his periodic table of effects? http://www.cs.missouri.edu/~harrisonwl/Presentations/UIUCFM05.ppt I've never seen a definition of the monad itself... http://www.haskell.org/pipermail/beginners/2010-January/003371.html ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Generalizing (++) for monoids instead of using ()
It is somewhat idiomatic to read it as TeX's \diamond symbol. Various papers set with Lhs2TeX use it for general composition operator (sometimes concat / mappend). On 2 April 2012 10:05, Yves Parès yves.pa...@gmail.com wrote: Plus one might argue that using to mean different is a bad choice, as it graphically means strictly inferior or strictly superior which implies comparability, whereas equality and comparison are two different things. (e.g. Eq and Ord are two distinct classes in Haskell). ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] for = flip map
I've always thought this was missing for parser combinator libraries as there is the notational tradition from YACC etc. to have production at the left then action at the right. On 29 March 2012 22:03, Sjoerd Visscher sjo...@w3future.com wrote: or perhaps infixr 0 $$ ($$) = flip ($) xs $$ \x - ... ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Fail-back monad
Maybe this is a version of William Harrison's DebugT monad with rollback, listed in his periodic table of effects? http://www.cs.missouri.edu/~harrisonwl/Presentations/UIUCFM05.ppt I've never seen a definition of the monad itself... http://www.haskell.org/pipermail/beginners/2010-January/003371.html ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] How to handle C library dependencies on Hackage?
Hi Christian Usually people host the documentation on their own site and put a link in the description field of the cabal file, pointing users to it. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Un-memoization
Hi Victor There was a paper at one of the early PADL conferences describing out-out-core data structures in Ocaml. I've never seen anyone following up this work, possibly because RAM has got so cheap in the last decade. If you have such large trees you may find the paper interesting. Although the authors used Caml they did use monads. Tyng-Ruey Chuang and Shin-Cheng Mu, Out-of-core functional programming with type-based primitives, The paper seems to be on Citeseer. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] MSIL manipulation libraries
I think there are two libraries for CIL on Hackage, one is for Microsoft's CIL (aka MSIL) the other is for George Necula et als CIL (C Intermediate Language). Obviously you want the one for Microsoft CIL. http://hackage.haskell.org/package/language-cil ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] HughesPJ vs. Wadler-Leijen
A quick suggestion - does setting the ribbon_frac to something like 0.8 improve things? The Show instance for wl-pprint's Doc uses 0.4 which I've found too low. This means you'll have to write your own display function using `renderPretty`... ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] HughesPJ vs. Wadler-Leijen
Ahem - there was a severe typo in my last message. Usually I wouldn't spam the list to repair my failings but edit distance on the error in that message was so large it made no sense at all. printing that cannot be undone by `group`, or the combinators that use group are given more long-winded **names** to make them secondary. I've bits and bobs on the go to do this, but nothing near a concrete library. Apologies to all. (Funny how I can spot typos after the fact...) ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Google Summer of Code idea of project application
Hi Damien A translator might be a lot of work. Matthew Naylor had a translator between Haskell and Clean [1], which performed well according to [2]. The translator was his Master project in the UK so I think that means it would represent approximately a years work. [1] http://www-users.cs.york.ac.uk/~mfn/hacle/hacle.pdf [2] http://www.st.cs.ru.nl/papers/2010/groj10-Haskell_front_end_Clean.pdf The paper [2] covers the Clean groups own interop between Haskell and Clean and points to more related work alongside Matthew Naylor's. Best wishes Stephen ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] cabal-install problem with alex dependency in bytestring-lexing
Alex is supplied as part of the Platform though which is the recommended system for beginners, is Yesod currently in advance of the Platform? On 16 March 2012 10:56, Erik de Castro Lopo mle...@mega-nerd.com wrote: The problem is that many of the people trying out Yesod are newcomers to Haskell. They are going to try cabal install yesod and have it fail because alex is missing. This is not a good introduction Haskell/Yesod. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Adding type annotations to an AST?
Hi Sean Many thanks - the note on flow-issues might be particularly helpful for me (last para section 4 introduction). My current code has a bug which maybe this identifies. I'm currently using a modified algorithm M which I believe is top down, I'll switch to algorithm W. Thanks again Stephen ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] using mutable data structures in pure functions
There is a trick to `nub` where you couldn't implement the internal lookup list with an (assumed faster) search tree anyway. `nub` only mandates equality not ordering, so building a ordered structure like a binary tree is impossible. In practice i would be hard to beat list as the intermediate structure in this case. On 12 March 2012 03:38, E R pc88m...@gmail.com wrote: [Chop] For example, consider the definition of Data.List.nub: nub l = nub' l [] where nub' [] _ = [] nub' (x:xs) ls | x `elem` ls = nub' xs ls | otherwise = x : nub' xs (x:ls) Clearly the memory allocated to ls never escapes nub', so it seems that ls could be replaced with a mutable data structure (with an eye towards improving performance in special cases). ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Adding type annotations to an AST?
Hi Oleg - many thanks
On 6 March 2012 07:15, o...@okmij.org wrote:
How do I add type annotations to interior locations in an abstract
syntax tree?
{Snip}
Here is the solution
http://okmij.org/ftp/Computation/FLOLAC/TEvalNR.hs
There is a bit of the explanation here:
http://okmij.org/ftp/Computation/FLOLAC/lecture.pdf
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Re: [Haskell-cafe] Adding type annotations to an AST?
Partially answering my own question - it seems like I want type directed translation as per section 8 of Practical Type Inference for Arbitrary Ranked Types. Does anyone know of a presentation with a simpler type language? Thanks again Stephen ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Adding type annotations to an AST?
Hello All How do I add type annotations to interior locations in an abstract syntax tree? I have a small ML language where programs are a single expression, but the expression type has let-rec so it supports recursive function definitions. Source programs have no type annotations. I want to annotate the lec-rec with type annotations, but my type inference is a simple implementation of Algorithm J so it seems monolithic to me - i.e. the type it infers is the type of the whole program, I would also like the types of any internal let-rec definitions so I can label my AST. What is the idiom for accomplishing this? I'm using Eijiro Sumii's MinCaml as reference - this embeds mutable references for types in the AST. So this appears a non-starter. My other thought is to uniquely label all type locations during parsing then collect them in a map (location - type) whilst computing the outermost type - I presume I can identify inner types as they are resolved during Algorithm J's run... Any solutions? Many thanks Stephen ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Impact of try on Parsec performance
I'd suggest `try` can make parsers had to debug and fragile when refactoring. `try` is very useful for char parsers, where you don't really want to be sharing a prefix amongst different parsers. For regular parsers you have equivalents of the EBNF operators plus the `sepBy` etc. parsers so the obsessive left recursion removal you see in text books isn't so burdensome - you have combinators to help you do it rather than having to rely on introducing more productions. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Does somebody know about these functions?
On 28 February 2012 17:06, Johan Holmquist holmi...@gmail.com wrote: Function 'withPair' takes a pair and applies a function to it's first element, another function to it's second element and finally combines the results with yet another function. withPair :: (a' - b' - c) - (a - a') - (b - b') - (a,b) - c withPair f fa fb (a,b) = fa a `f` fb b withPair is the Dovekie function from combinatory logic but with a pair for the non-combinator arguments (a,b) and the arg order changed to be more convenient to program with. There was a thread about inter[*] on the beginners list last month http://www.haskell.org/pipermail/beginners/2012-January/009329.html [*] or an inter-like function depending how you want to treat the initial value. I made a mistake with my suggestion. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Using multiplate to get free variables from a syntax tree
I'm not familiar with Multiplate either, but presumably you can descend into the decl - collect the bound vars, then descend into the body expr. Let $ decl child d * expr child e This seems like a common traversal that Strafunski would handle, and with Multiplate being a competitor / successor to Strafunski it should be able to do it too. Naturally you would need a monadic traversal rather than an applicative one... ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] C++ Parser?
There is also the DMS from Ira Baxter's company Semantic Design's. This is an industry proven refactoring framework that handles C++ as well as other languages. I think the Antlr C++ parser may have advanced since the article Antoine Latter link to, but personally I'd run a mile before trying to do any source transformation of C++ even if someone were waving a very large cheque at me. On 24 January 2012 14:54, Christopher Brown cm...@st-andrews.ac.uk wrote: Hi Everyone, Thanks for everyone's kind responses: very helpful so far! I fully appreciate and understand how difficult writing a C++ parser is. However I may need one for our new Paraphrase project, where I may be targeting C++ for writing a refactoring tool. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] generating parens for pretty-printing code in haskell-src-exts
Hi Conal I don't know if any Haskell src-exts code exists. Norman Ramsey has published an algorithm for it, plus ML code: http://www.cs.tufts.edu/~nr/pubs/unparse-abstract.html I've transcribed the code to Haskell a couple of times for small expression languages. As far as I remember you need to know what constructors you are working with so it can't be put in a generic pretty print library, but the constructor specific code is stereotypical so it should be easy (if boring) to write for Haskell src-exts. Best wishes Stephen ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Are all monads functions?
On 31 December 2011 12:26, Jerzy Karczmarczuk jerzy.karczmarc...@unicaen.fr wrote: Yves Parès : all standard Monads are newtypes wrapping functions What about Maybe and [] ? And Identity ... ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Avoiding parametric function binding
Maybe you want a deconstructor (sometime called an eliminator)? deconsVar :: (Maybe Int - a) - (Maybe String - a) - Var - a deconsVar f g (V1 a) = f a deconsVar f g (V2 b) = g b ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] MIDI-controlled application
Hi Tim Events in FRP / Yampa are typically key presses / mouse movement, so a MIDI controller generating Note-on / Note-off events would be a direct analogue to key presses. More problematic is that FRP models hybrid (continuous and discrete) systems. For me at least, MIDI seems essentially discrete - a stream of control events. In MIDI files control events are twinned with a time stamp so they can be played. Presumably events are instantaneous in real-time interactive MIDI - not something I've looked at. Working with an FRP system like Yampa might add a lot of complexity, which admittedly you should be able to ignore - but initially it might be difficult to identify what parts are needed for a mostly discrete system like MIDI. (If you are time-stamping MIDI events yourself you will presumably need to sample a running clock which seems like a continuous behaviour...) Unfortunately I can't think of any systems in Haskell that are more discrete than continuous so you might have to choose a FRP system anyway. Incidentally, I've been working on a MIDI animation language for the last couple of days based on the animation language in Paul Hudak's book. I've wanted continuous behaviours to model modulating volumes (crescendos, decrescendos) and panning, but I've found the work tough going for modelling the note lists where I want the system discrete in both input (specification) and output. Best wishes Stephen ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Generating Code
Geoffrey Mainland did significant work generating C with his GHC quasi quote extension. I'm not sure the status or availability of the code but there was a good Haskell Workshop paper describing it. For the specific problem of OpenGL - as the package already exists I'm not sure a generative approach would actually pay its way ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Anonymous, Unique Types, maybe
Umm, an obvious point is that if you really are using lists as streams they should appear infinite to the processing code, so you shouldn't encounter operations that fail due to incompatible lengths. Otherwise I think there might be packages on Hackage for fixed sized lists, its a common example for the power of GADTs, though personally I've found size annotated lists unusable at the point where I need `filter` (which you are calling mySelect?). ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Interpreter with Cont
On 21 November 2011 14:48, Yves Parès limestr...@gmail.com wrote: I've read Martin Erwig and Steve Kollmansberger's Probabilistic functional programming in Haskell. Does someone know if the library they are talking about is available on hackage? Henning Thielemann has a batteries included version on Hackage: http://hackage.haskell.org/package/probability I'd expect the original (micro) library is still available from Martin Erwig's website. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Tutorial/slides on pretty-printing combinators?
Hi Sean Doaiste Swierstra has fairly extensive notes on the development of the attribute grammar versions of uulib's pretty printers. The notes are called Designing and Implementing Combinator Languages. As they were a showcase for UUAG there is quite a lot on attribute grammars in the notes, but the should be still be a good source of inspiration. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] deepseq-1.2.0.1 missing Data.Map instance
Hello Henry I think it is a case of the dependency changing recently from deepseq depending on containers to containers depending on deepseq. Thus you want to check you are using compatible versions of deepseq and containers. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] ANN: diagrams 0.4
Rustom Mody rustompm...@gmail.com writes: I remember (vaguely) a 'live page' ie where one could enter (into the browser) changes to the diagrams code and see the results immediately. Is that page there? (Or am I mixing up with something else?) Maybe it was Péter Diviánszky's 'dia' (entirely different to 'diagrams') ? http://pnyf.inf.elte.hu/fp/Diagrams_en.xml ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] lost in generics
On 20 October 2011 18:12, Rustom Mody rustompm...@gmail.com wrote: I need some help finding my way around the various generics libraries. My usage scenario is -- at least to start with -- the ASTs of programming languages. In general my question is: What is alive/active and what is alive/active and what is -- um -- moved-on-from. And of course which are easier and which more difficult to dig into. I'd group Strafunski, Uniplate and Kure together as they are all have extensive traversal control. Uniplate is a good choice as it is well documented and in active use. Kure is good if you know Strafunski, but might be a struggle to work with otherwise. Strafunski was pre-Hackage and used Drift for pre-processing so installing it nowadays would be a challenge. However, Strafunksi is well documented, especially the Design Patterns for Functional Strategic Programming[*] paper. Its worth reading this even if you don't use Strafunski. [*] http://arxiv.org/abs/cs/0204015 ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] ANNOUNCE: vector-bytestring-0.0.0.0
On 19 October 2011 15:59, AM age...@themactionfaction.com wrote: Note that other programming languages have had to solve this exact problem and they usually end up with multiple functions- one for debugging, one for serialization, one for displaying how the object was constructed. As per Haskell with Show (representation) and Data.Binary (serialization), of course. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Comparison Haskell, Java, C and LISP
Haskell has no support for reflection whatsoever. It can support compile time meta-programming with Template Haskell. Reflection itself might be antagonistic to functional programming, I suspect it is at odds with referential transparency. Most of the work on reflection seemed based around Lisp / Scheme - Christian Queinnec's reflective interpreter in Lisp in Small Pieces uses an awful lot of set! ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] ANNOUNCE: vector-bytestring-0.0.0.0
On 15 October 2011 23:56, Bas van Dijk v.dijk@gmail.com wrote: On 15 October 2011 23:17, Ertugrul Soeylemez e...@ertes.de wrote: Both instances are valid here, and there is no mechanism to choose one of them. There is: OverlappingInstances[1] chooses the most specific instance. So in case someVector :: Vector Word8 the instance Show (Vector Word8) is chosen because it's the most specific. This has the problem of incoherence in multi-module programs - GHC might chose different instances for the same type depending on compilation order. For a Show instance, this may be acceptable. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] ANNOUNCE: vector-bytestring-0.0.0.0
On 16 October 2011 10:06, Bas van Dijk v.dijk@gmail.com wrote: But is this a problem when both instances are exported from the same module and OverlappingInstances is only enabled in that module, as is the case here? No - if the only instances defined are in the same module GHC would pick the most specific one. If there was no instance for Ivan's use-case of Vector Word8 in the offical module, and he chose to define this more specific instance elsewhere there is the potential for incoherence. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] DSL for data definition (e.g. compiling Haskell type defs into Google's protocol buffers type defs)
On 4 October 2011 17:02, Karel Gardas karel.gar...@centrum.cz wrote: Hello, [SNIP] So basically speaking I'm thinking about using Haskell sub-set as a data-definition DSL together with some functions which will generate some code based on supplied defined data types. ... This seems reminiscent of ASDL - the Abstract Syntax Definition Language - and ASDLgen (its generator) which used sum and product types (essentially the same a Haskell or ML's algebraic types) to define data for compiler internals. The definitions could be compiled to C++, C, Java, ML, and Haskell. As well as data type definitions ASDLgen generated marshallers for the ASDL binary format. Unfortunately the Zephyr project which sponsored ASDL seems to have had an early demise - so what info there still is available on the web might be patchy. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] hackage library info
Hi There have been plans to add rankings to Hackage and a GSOC looked into adding them. Roel van Dijk built reverse dependencies for Hackage which illustrated the most popular libraries, unfortunately the link seems broken: http://bifunctor.homelinux.net/~roel/hackage/packages/hackage.html Of course, the best library for you is the one that does more of want you need in a way that you like the most. Social proof might not always help for this... Best regards Stephen ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Categorized Weaknesses from the State of Haskell 2011 Survey
Replying to someone's compliant in the first section: Malcolm Wallace and Colin Runciman's ICFP99 paper functioned well as a tutorial for HaXml when I used it - maybe it is a bit out of date now? HaXml is hardly a dire case. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Solving the configuration problem with parametrized modules
On 6 September 2011 15:33, Joachim Breitner m...@joachim-breitner.de wrote: I think the benefit you get from being able to treat runtime constants as plain values manifests mostly when writing pure code. If your code has already been written or re-written in monadic style, adding a transformation layer is indeed less of a problem. Run time constants are still an effect, though, just like error, state, IO... that's why they are usually propagated with the Reader monad or sometimes implicit params. This does seem to irritate newcomers on Stack Overflow who don't equate constant (but not statically known) values with more active effects like state or file IO. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Smarter do notation
It seems like complication for very slight advantage. Firstly, so far only UU Parsing and Trifecta appear to have optimized Applicative instances (does the optimization work for mixed Monad+Applicative parsers or only if the whole parser is Applicative?). Secondly if you want Applicative then you can write in the Applicative style, often as succinct as do-notation. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Question about data
Others have pointed out your first bug. To get floating-point numeric literals you will need to define instances of Num and then Fractional for your symbolic type. On 19 August 2011 21:40, Paul Reiners paul.rein...@gmail.com wrote: *Main let pi = 3.14 :: MathExpression ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Hiding growing state using existentials.
You can't define (=) if your state type changes: (=) :: m a - (a - m b) - m c Whereas, your bind is effectively three different parametric types: _bind :: m1 a - (a - m2 b) - m3 b You can use parametric monads to represent state changing within a monad. Oleg Kiselyov has tutorials on their use on his website (search for the Monadish class). The SHE experimental extension of Haskell also has parametric monads built in. bindish :: m s1 a - (a - m s2 b) - m s2 b I don't think parametric monads will solve your problem though, as you want a product of the states as the result of bind. Are you really sure you want this behavior?, I'd imagine it breaks the monad laws anyway. http://okmij.org/ftp/Computation/monads.html ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] library on common sub-expression elimination?
Wouldn't this be dependent upon your AST and thus not readily package-able as a library? Expression simplification has been a prime example for Strafunski style traversal libraries. You might be able to find examples that you can adapt to your own AST written with Uniplate or similar library. On 11 August 2011 05:00, Anton Kholomiov anton.kholom...@gmail.com wrote: Is there a library on common sub-expression elimination? ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] library on common sub-expression elimination?
Strafunski and its successors (Uniplate, SYB, KURE) are really for working on trees. If you want to work on graphs you would probably be better of with something else. I think I overlooked that you want common sub-expression _elimination_, rather than expression simplification. There are libraries for observable sharing (Andy Gill's recent one is the state-of-the-art, its on Hackage but I've forgotten its name) - that are pertinent where you have built the expressions as an embedded DSL in Haskell and you want sharing in code you generate from the Haskell DSL. On 11 August 2011 08:57, Anton Kholomiov anton.kholom...@gmail.com wrote: Thank you for the reference to Strafunski libraries, I read HaskellWiki, but I don't have a permission to visit their site. All links are forbidden. Can it be a function: fun :: Eq a = Tree a - [(Int, (a, [Int]))] where tuple codes nodes, and Int's code edges. 2011/8/11 Stephen Tetley stephen.tet...@gmail.com Wouldn't this be dependent upon your AST and thus not readily package-able as a library? Expression simplification has been a prime example for Strafunski style traversal libraries. You might be able to find examples that you can adapt to your own AST written with Uniplate or similar library. On 11 August 2011 05:00, Anton Kholomiov anton.kholom...@gmail.com wrote: Is there a library on common sub-expression elimination? ___ 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] Idiomatic ways to make all instances of a certain class also instances of another?
For: instance (Ord a) = Max a where maximum = max The same could more simply be achieved with a function: maximum :: Ord a = a maximum = max Now, you probably wanted both a base-case using max and type specific, special cases: instance Max Int where maximum = 2^16 If you have both instances defined in the same module, GHC should always pick the special case for Int if overlapping instances is turned on. However, I've never found a description of how it resolves instance selection if you have the specialized cases in different modules. Unspecified [*] behaviour is not something I'd want to rely on, so I always avoid Overlapping Instances. [*] Of course, the multiple module behaviour might be specified somewhere... ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Grammar hacker in Haskell
The algorithms are common practice and a web search should provide lecture notes detailing them - you will likely have to translate to Haskell yourself. If you have a university affiliation, I'd go to the library and check books on compiler construction. The classic is the Dragon Book - Compilers: Principles, Techniques, and Tools by Aho et al. though the presentation in this book is quite formal. I liked Modern Compiler Design by Grune et al. myself. Be cautious about buying a book without surveying it first - the presentation of the algorithms varies considerably. Best wishes Stephen ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Introspection
As Haskell is statically typed, if y.length 100, y is still of type Big... On 22 July 2011 10:18, Patrick Browne patrick.bro...@dit.ie wrote: 2) Assert the type of a variable e.g. if y.length 100 then y is of type big. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Grammar hacker in Haskell
On 22 July 2011 16:32, Johannes Waldmann waldm...@imn.htwk-leipzig.de wrote: Stephen Tetley stephen.tetley at gmail.com writes: Compilers: Principles, Techniques, and Tools by Aho et al. though the presentation in this book is quite formal. you make that sound like a bad thing ... Well - not intentionally, and for the cognoscenti formal presentations can often be translated to a high-level language like Haskell more easily than say pseudo code; but if you don't have much prior experience I'd think something at the Dragon Book's level would be quite demanding. Myself, I bought the Grune et al. book after getting stranded with the Dragon Book. Working through the Grune made reading the Dragon Book a lot more accessible. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Constructor discipline and dependent types.
On 17 July 2011 10:03, Patrick Browne patrick.bro...@dit.ie wrote: Question 1: Is the above a reasonable understanding of CD? From a brief look, constructor discipline (CD) restricts left-hand sides of equations to have no function calls themselves. http://users.dsic.upv.es/~gvidal/german/pepm97/paper.pdf ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Baffling Hackage build log
This seems to be a general problem with the Hackage server as other packages uploaded after yours have failed to build with similar errors... ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
