[Haskell-cafe] Eager Parser Combinators [was: Functional programming for processing of largeraster images]

[Jared Updike]

On 6/22/06, Greg Buchholz <haskell at sleepingsquirrel.org> wrote:
> Ralf Hinze wrote:
> > Also, in a non-strict language recursive definitions are not
> > limited to function types. Users of parser combinators heavily rely
> > on this feature. Just try to define/use parsing combinators
> > ins a strict language.
>
>     Anyone care to comment on what goes wrong with parser combinators in
> an eager language?  Is it mainly a space usage problem (where the lazy
> version might essentially perform a depth-first-search, while the eager
> version is breadth-first)?  Or is there something else I'm missing?

Slide 22 ("Combinator Libraries") of
  http://research.microsoft.com/~simonpj/papers/haskell-retrospective/
shows that in an eager language, you have to make the argument
explicit, which destroys the Parser abstraction. Indeed I rolled my
own sort of monads and made my own parser combinators in C# and they
were a lot like your Perl combinators: very imperative and verbose
(~10x more code than Haskell for the same parser), instead of clean
and declarative like BNF or Haskell parser combinators.

  Jared.

>     As a reference, back when I was trying to understand monads, I
> ported the parser combinators from the Hutton and Meijer paper to
> perl...
>
>     http://sleepingsquirrel.org/monads/parser/monad_parser.txt
>
>
> Thanks,
>
> Greg Buchholz
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