[Haskell-cafe] Newbie: Is it possible to catch _|_ ?
spamhole-2001-07-16 at deming-os.org
Sat Apr 10 03:00:54 EDT 2004
Thanks guys for the links to parsers.
I wasn't so much looking for a parser as I was exploring the mappings of
algorithms. One of my passions is to explore how different computer
programming languages interrelate. In particular, I am fascinated with
the concept of transforming a program in one language into another
language. A parser language is, almost by definition, the specification
of a transform (from a linear structure to a heirarchal one), so I am
very interested in different ways to build parsers, as then I'm
transforming a transform....
Matthew Walton wrote:
> Isn't Happy  a bottom-up parser generator in the style of yacc?
>  http://www.haskell.org/happy/
> As for parsing yacc's input files, if you can come up with an EBNF
> grammar for it that avoids some of the nasty recursion possibilities
>  then I can't see why you couldn't parse it with Parsec or some
> other parsing library. Or even with a parser written using Happy.
> Parsec's not that bad really, but the HuttonMeijerWallace one is
> easier if you start off with those and move to Parsec if you need a
> more powerful solution. But I may be biased as I'm a former student of
> Graham Hutton's.
> With all the choices available though there's not much point writing
> your own unless you've got very unusual requirements, something new to
> bring to the table, or you like the challenge.
> So I would definitely recommend HuttonMeijerWallace or Parsec if
> you're wanting to parse something. It's possible Happy-generated
> parsers run faster, but I don't really know and I was quite content
> with Parsec's speed when I used it in my final-year project. Not that
> it was parsing anything particularly huge at the time.
>  http://www.haskell.org/happy/
>  the proper terms for which I can't remember, but I seem to recall
> that left recusion is one of the nasty ones
> Graham Klyne wrote:
>> I'm not familiar with yacc, but I understand that it's a bottom-up
>> parser generator. I've not come across any bottom-up parser
>> generators written in Haskell.
>> I have seen (at least) three examples of top-down parser generators
>> coded in Haskell:
>> (1) in Simon Thompson's book, the Craft of Functional Programming. I
>> have done an implementation based on these ideas , which I have
>> since discarded in favour of Parsec...
>> (2) the Parsec parser library , which is a very full-functioned
>> and easy-to-use library, but which might be not-so-easy for a Haskell
>> newcomer to figure out its internal workings because it is heavily
>> based on Monads.
>> (3) the HuttonMeijerWallace parser combinator library , which is
>> also based on a Monad but, being less complex, is easier to follow
>> its internals.
>>  http://www.cs.uu.nl/~daan/parsec.html
>> (also in the Haskell hierarchical libraries, under 'text'.
>>  API Documentation:
>> Source in CVS:
>> Being part of HaXml:
>>  http://www.ninebynine.org/Software/HaskellUtils/Withdrawn/Parse.hs
>> (And related code in same directory. This was just about the first
>> real program I write in Haskell, so don't look to this for an example
>> of how one *should* program using Haskell!)
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