Combinators for ReadP

Simon Peyton-Jones simonpj at microsoft.com
Mon Jul 26 12:14:03 EDT 2004


Koen, not me!

Simon

| -----Original Message-----
| From: libraries-bounces at haskell.org [mailto:libraries-bounces at haskell.org] On Behalf Of Malcolm
| Wallace
| Sent: 26 July 2004 17:04
| To: libraries at haskell.org
| Subject: Re: Combinators for ReadP
| 
| Martin Sjögren <msjogren at gmail.com> writes:
| 
| > > I think you'll find that without the local universal quantifier,
| > > you cannot make ReadP a (useful) instance of Monad, because your
| > > 'r' parameter would be fixed across >>=, whereas it really needs to
| > > be variable.
| >
| > Uhh. But it works for ContT, so why not for ReadP? The only point time
| > you have to fix the r is when you want to "run" the parser, all other
| > parsers will be polymorphic in r:
| 
| OK, cool.  If you can successfully convert ReadP to Haskell'98, we'd
| all be delighted.  But Koen and Simon PJ are the people most likely
| to be able to give relevant comment on whether any subtle properties
| will be lost.
| 
| Regards,
|     Malcolm
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