precedence bug with derived instances
In GHC 5.04.1, derived instances of Show mishandle precedence: Prelude putStrLn (showsPrec 10 (Just 0) ) Just 0 Prelude The result should be: (Just 0) ___ Glasgow-haskell-bugs mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
RE: Using Bison as Haskell parser generator
(I am currently not on this list, so replies, please cc me.) The later versions of the GNU parser generator Bison, like ftp://ftp.gnu.org/gnu/bison/bison-1.75.tar.gz (959 KB) ftp://ftp.gnu.org/gnu/bison/bison-1.75.tar.bz2 (759 KB) use the macro processing program M4 to produce the source code output. This should make it real easy to write parser generator (skeleton) files designed for special languages. So I wonder if somebody may want to make an attempt to produce such skeleton files for Haskell. Bison has now not only an LALR(1) parser algorithm, but also a GLR parser, and more is to come. Note that Happy has support for some Haskellish things which you won't get if you use bison to generate Haskell. For example: type signatures on productions, and support for threading a monad around the parser. Nevertheless, doing this sounds entirely feasible. The parser tables generated by bison are very similar to those generated by Happy (I peeked at bison's source when I wrote the table-generation code in Happy), so looking at Happy's LALR(1) machine might be a good place to start. Cheers, Simon ___ Haskell mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/haskell
RE: Using Bison as Haskell parser generator
tor 2002-10-17 klockan 17.32 skrev Simon Marlow: Note that Happy has support for some Haskellish things which you won't get if you use bison to generate Haskell. For example: type signatures on productions, and support for threading a monad around the parser. Another feature which I would love to have in Happy is support for more EBNF stuff, like repetition and alternative. Repetition maps to Haskell lists and alternative maps to haskell Maybe. Since there exists a transformation from EBNF to BNF this should be possible. Also, the transformation can take certain things into account, like that parsing a list of things is best done like this (due to the parser being LALR) list_of_things ::= empty | list_of_things thing instead of this more natural way list_of_things empty | thing list_of_things Regards, Martin ___ Haskell mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/haskell
RE: Using Bison as Haskell parser generator
At 16:32 +0100 2002/10/17, Simon Marlow wrote: So I wonder if somebody may want to make an attempt to produce such skeleton files for Haskell. Bison has now not only an LALR(1) parser algorithm, but also a GLR parser, and more is to come. Note that Happy has support for some Haskellish things which you won't get if you use bison to generate Haskell. For example: type signatures on productions, and support for threading a monad around the parser. I am not sure what these type signature are: But Bison has a typing feature currently only used with the implementation of unions. It is easy to tweak to become only a typing feature (not tied to C union in implementation). By macros, one can then write out a suitable form of the semantic variables to extract the correct typing. I am not sure what exactly this threading a monad around the parser means: But under C++, I am now wrapping C++ namespaces around my parser. I have suggested that Bison should get a construct %define name definition producing a suitable macro handed over to M4. Thus, I should be able to write %defined namespace name and exploit that to create a suitable namespace around the parser. Such a procedure is sufficiently general that it ought to be able to handle your monad wrapping as well. -- But one can only know for sure by actually trying, and the feedback from such a try might be interesting. Nevertheless, doing this sounds entirely feasible. The parser tables generated by bison are very similar to those generated by Happy (I peeked at bison's source when I wrote the table-generation code in Happy), so looking at Happy's LALR(1) machine might be a good place to start. Then interaction between Happy and Bison might turn out to be interesting. The Bison people may also want parser generator sources in other languages, functional like LISP (Scheme), SML, as well as others. I am not myself actively programming in Haskell now, so that is one reason I posted it. I should have mentioned that more info about Bison can be found on its mailing lists: [EMAIL PROTECTED] http://mail.gnu.org/mailman/listinfo/help-bison [EMAIL PROTECTED] http://mail.gnu.org/mailman/listinfo/bug-bison Hans Aberg ___ Haskell mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/haskell
The Implementation of Functional Programming Languages
Hello. Is the book The Implementation of Functional Programming Languages, by Simon Peyton Jones, available in the internet? This book is out of print. Romildo -- Prof. José Romildo Malaquias[EMAIL PROTECTED] Departamento de Computação [EMAIL PROTECTED] Univ. Federal de Ouro Preto http://uber.com.br/romildo ___ Haskell mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/haskell
Re: The Implementation of Functional Programming Languages
I remember I downloaded from his homepage. Good luck. On Thu, 17 Oct 2002, Jose Romildo Malaquias wrote: Hello. Is the book The Implementation of Functional Programming Languages, by Simon Peyton Jones, available in the internet? This book is out of print. Romildo -- Prof. José Romildo Malaquias[EMAIL PROTECTED] Departamento de Computação [EMAIL PROTECTED] Univ. Federal de Ouro Preto http://uber.com.br/romildo ___ Haskell mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/haskell ___ Haskell mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/haskell
Re: The Implementation of Functional Programming Languages
On Thu, Oct 17, 2002 at 12:49:01PM -0700, Deling Ren wrote: I remember I downloaded from his homepage. Good luck. I could not find it in his homepage. The only related book I found there is Implementing functional languages: a tutorial, by Peyton Jones and Lester: http://research.microsoft.com/Users/simonpj/Papers/pj-lester-book/ Would you remember the url you have used to tell me? On Thu, 17 Oct 2002, Jose Romildo Malaquias wrote: Is the book The Implementation of Functional Programming Languages, by Simon Peyton Jones, available in the internet? This book is out of print. Romildo -- Prof. José Romildo Malaquias[EMAIL PROTECTED] Departamento de Computação [EMAIL PROTECTED] Univ. Federal de Ouro Preto http://uber.com.br/romildo ___ Haskell mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/haskell
representation getting verbose...
Greetings Haskellers, I'm running into a problem representing some fairly complicated types, and I'll try to put together a simpler example to get your suggestions. In Paul Hudak's SOE, I find a definition of expression: data Expr = C Float | V String | Expr :+ Expr | Expr :- Expr | Expr :* Expr | Expr :/ Expr Now this is compelling, but sometimes, I might want to have a function that takes a variable only, not just any kind of expression. I could write something like: typeOfVariable :: Expression - Type typeOfVariable (V s) = ... _= error... But thats not very satisfying from a type-checking perspective. So it makes sense to create a constructor: data Variable = VVariable String data Expr = C Float | V Variable | Expr :+ Expr | Expr :- Expr | Expr :* Expr | Expr :/ Expr and make typeOfVariable :: Variable - Type. But then when I want to match or create a variable expression, things are starting to get verbose: case expr of C f - ... V (Variable (VVariable s)) - ... ... And if I want a still more accurate hierarchy, the construction and destruction of Variables can really become cumbersome. For an interpreter I'm writing, I found myself writing a function constructVarExpr :: String - Expr just to make it easier. This all seems very inelegant, and I get the feeling that there's a better way to do this. Any suggestions on how I could better represent Expressions or Variables to keep the type-checking but decrease the verbosity? peace, Isaac Jones ___ Haskell-Cafe mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: Wiki problems
John C. Peterson [EMAIL PROTECTED] writes: We're aware of the wiki problems. We've got out wiki guy working on it and I hope everything will be working again soon. We won't lose anything that's been posted to the wiki. Please be patient! At one point in the distant past there was the idea of switching to another wiki flavor such as MoinMoin. I'd be willing to translate the content from pywiki to MoinMoin if there's still interest. That could be a permanent fix to the continuing missing pages problem. -- Shae Matijs Erisson - 2 days older than RFC0226 ___ Haskell-Cafe mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/haskell-cafe
