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Re: Type classes vs Java interfaces (Peter Hall) 6. cabal-debian (Ryan) ---------------------------------------------------------------------- Message: 1 Date: Thu, 31 Jan 2013 19:55:56 +0530 From: Rustom Mody <rustompm...@gmail.com> Subject: Re: [Haskell-beginners] Literate Haskell - capturing output To: Martin Drautzburg <martin.drautzb...@web.de> Cc: beginners@haskell.org Message-ID: <CAJ+TeociEmb0B99MG1ab+eCdG-JEz=hmui_71v3o9a7rth5...@mail.gmail.com> Content-Type: text/plain; charset="iso-8859-1" On Fri, Jan 18, 2013 at 12:30 AM, Martin Drautzburg < martin.drautzb...@web.de> wrote: > Hello all, > > I am using literate haskell quite a lot (otherwise I don't understand my > own > code). This works fine for the code as such. But when I give an example > usage, > I run code snippets in ghci and copy&paste into the main document/program, > which turns them into "text" (and not code). > > When I make changes to the program these examples tend to no longer reflect > the actual program. > > Is there a way to automatically run examples and include them in the .lhs > file, preferably with the haskell prompt and everything? > > If you are ok with emacs, emacs -> orgmode -> babel may be worth a consider http://orgmode.org/worg/org-contrib/babel/intro.html http://www.jstatsoft.org/v46/i03/paper -- http://www.the-magus.in http://blog.languager.org -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://www.haskell.org/pipermail/beginners/attachments/20130131/7cbeef10/attachment-0001.htm> ------------------------------ Message: 2 Date: Thu, 31 Jan 2013 20:12:22 +0530 From: Rustom Mody <rustompm...@gmail.com> Subject: Re: [Haskell-beginners] Literate Haskell - capturing output To: Martin Drautzburg <martin.drautzb...@web.de> Cc: beginners@haskell.org Message-ID: <caj+teodf8bqwwa1cwfjrpbwcfxm4ywa5arlh8wfjuvkt7c-...@mail.gmail.com> Content-Type: text/plain; charset="iso-8859-1" On Thu, Jan 31, 2013 at 7:55 PM, Rustom Mody <rustompm...@gmail.com> wrote: > > > On Fri, Jan 18, 2013 at 12:30 AM, Martin Drautzburg < > martin.drautzb...@web.de> wrote: > >> Hello all, >> >> I am using literate haskell quite a lot (otherwise I don't understand my >> own >> code). This works fine for the code as such. But when I give an example >> usage, >> I run code snippets in ghci and copy&paste into the main document/program, >> which turns them into "text" (and not code). >> >> When I make changes to the program these examples tend to no longer >> reflect >> the actual program. >> >> Is there a way to automatically run examples and include them in the .lhs >> file, preferably with the haskell prompt and everything? >> >> > If you are ok with emacs, > emacs -> orgmode -> babel may be worth a consider > http://orgmode.org/worg/org-contrib/babel/intro.html > http://www.jstatsoft.org/v46/i03/paper > > > http://www.cs.unm.edu/~eschulte/data/CISE-13-3-SciProg.pdf maybe a better read -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://www.haskell.org/pipermail/beginners/attachments/20130131/ea6befab/attachment-0001.htm> ------------------------------ Message: 3 Date: Thu, 31 Jan 2013 16:40:49 +0000 From: Sean Cormican <seancormic...@gmail.com> Subject: [Haskell-beginners] Using Parsec to parse Haskell Language To: beginners@haskell.org Message-ID: <CAF6xeQdRnywdM=xfngbCr=0ohi1gbr_yz7gvhtcw6v2si3f...@mail.gmail.com> Content-Type: text/plain; charset="iso-8859-1" I'm working on a project in which I am attempting to write a parser for Haskell within Haskell itself using Parsec. The parser itself only deals with a subset of the features of the full Haskell implementation but I'm having difficulty figuring out how to implement the grammar with precedence of operations for example boolean expression involving && over || and also 'if then else" statements in relation to other operations. I'm attempting to do this with the Text.Parsec.Expr module more specifically BuildExpressionParser combinator using table and term as used in a number of tutorials I have seen which deal with arithmetic expression. Is this the correct course of action? Or will it fail to meet my needs. Will it be necessary to create an AST for the grammar by creating new data types as outlined in the following tutorial? http://www.haskell.org/haskellwiki/Parsing_a_simple_imperative_language Also what's the difference between the modules: Text.Parsec.Expr Text.ParserCombinators.Parsec.Expr Thanks in advance, Se?n -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://www.haskell.org/pipermail/beginners/attachments/20130131/dc787da8/attachment-0001.htm> ------------------------------ Message: 4 Date: Thu, 31 Jan 2013 23:36:46 +0000 From: Mateusz Kowalczyk <fuuze...@fuuzetsu.co.uk> Subject: [Haskell-beginners] Type classes vs Java interfaces To: beginners@haskell.org Message-ID: <510b000e.5000...@fuuzetsu.co.uk> Content-Type: text/plain; charset=ISO-8859-1 Greetings, I often wonder how one would explain type classes to someone coming from an environment such as Java. Whenever I think about type classes, I seem to think of them as Java interfaces. Bah, even the bottom of [1] states > Haskell classes are roughly similar to a Java interface. Like an interface declaration, a Haskell class declaration defines a protocol for using an object rather than defining an object itself. Is there more to this `roughly similar' statement? Syntax is an obvious difference but beyond that, I can't think of anything I can do with a Haskell type class that I wouldn't be able to do with similar amount of effort with a Java interface, except for the fact that the interface would look absolutely disgusting syntax wise. Any insight appreciated. [1] - http://www.haskell.org/tutorial/classes.html ------------------------------ Message: 5 Date: Fri, 1 Feb 2013 01:43:16 +0000 From: Peter Hall <peter.h...@memorphic.com> Subject: Re: [Haskell-beginners] Type classes vs Java interfaces To: The Haskell-Beginners Mailing List - Discussion of primarily beginner-level topics related to Haskell <beginners@haskell.org> Message-ID: <CAA6hAk60ZuKC8KH-9h+mLdfjP8=ozrjeswh38lyrbrwt_nl...@mail.gmail.com> Content-Type: text/plain; charset="iso-8859-1" The Java type system is a lot less rich. You can take an object and call methods on it, knowing only that it implements an interface. In Haskell, you can do so much more. You don't even need an implementation, you can rely on the type of the binding instead: extremes :: Bounded b => Bool -> b extremes lower = if lower then minBound else maxBound -- e.g. extremes True :: Int -- -9223372036854775808 data Foo = A | B | C | D deriving (Bounded, Show) extremes False :: Foo -- D Or (with a few language extensions), you can have the typeclass take multiple arguments. In Java, you can't do anything like this: class Convert a b where convert :: a -> b instance Show a => Convert a String where convert = show instance Convert Foo String where convert A = "A" convert B = "B" convert C = "C" convert D = "D" Peter On 31 January 2013 23:36, Mateusz Kowalczyk <fuuze...@fuuzetsu.co.uk> wrote: > Greetings, > > I often wonder how one would explain type classes to someone coming from > an environment such as Java. Whenever I think about type classes, I seem > to think of them as Java interfaces. Bah, even the bottom of [1] states > > Haskell classes are roughly similar to a Java interface. Like an > interface declaration, a Haskell class declaration defines a protocol > for using an object rather than defining an object itself. > > Is there more to this `roughly similar' statement? Syntax is an obvious > difference but beyond that, I can't think of anything I can do with a > Haskell type class that I wouldn't be able to do with similar amount of > effort with a Java interface, except for the fact that the interface > would look absolutely disgusting syntax wise. > > Any insight appreciated. > > > [1] - http://www.haskell.org/tutorial/classes.html > > _______________________________________________ > Beginners mailing list > Beginners@haskell.org > http://www.haskell.org/mailman/listinfo/beginners > -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://www.haskell.org/pipermail/beginners/attachments/20130201/528c16b2/attachment-0001.htm> ------------------------------ Message: 6 Date: Fri, 01 Feb 2013 00:01:55 -0500 From: Ryan <rde...@gmail.com> Subject: [Haskell-beginners] cabal-debian To: beginners@haskell.org Message-ID: <510b4c43.1030...@gmail.com> Content-Type: text/plain; charset="iso-8859-1"; Format="flowed" Hello, I'm trying to compile a cabal package to debian with cabal-debian and having some trouble. git clone git://github.com/wavewave/hoodle.git cd hoodle/ cabal-debian --debianize --ghc --maintainer Ryan then I get a the following error: cabal-debian: cabal-debian: No bundled package list for ghc Version {versionBranch = [7,4,2], versionTags = []} shouldn't cabal-debian be pulling the package list from the hoodle.cabal file? Thanks, Ryan -------------- next part -------------- An HTML attachment was scrubbed... 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