[Haskell-cafe] Parsec 3 Description

Philippa Cowderoy flippa at flippac.org
Thu Sep 4 17:29:40 EDT 2008

On Thu, 2008-09-04 at 20:38 +0000, Duncan Coutts wrote:
> On Thu, 2008-09-04 at 19:41 +0100, Philippa Cowderoy wrote:
> > On Thu, 4 Sep 2008, John Van Enk wrote:
> > 
> > > I'm looking for a document describing the differences between Parsec 3 and
> > > Parsec 2. My google-foo must be off because I can't seem to find one. Does
> > > any one know where to find that information?
> > > 
> > 
> > Unfortunately there isn't currently a good one - in fact, it raises an 
> > issue with HackageDB, which is that there isn't a good way to handle both 
> > stable and working releases.
> The simple solution to this (which I may get round to implementing) is
> that for each package on hackage we have a suggested constraint (that
> the maintainer could set). For example for parsec we might use '< 3'.
> Then tools like cabal-install or distro package converters could take
> this into account when someone asks to install that package. This would
> not prevent packages explicitly requiring the later version as it'd only
> come into play when there are no other constraints and where the search
> algorithms just pick the highest version.

Cool. I imagine you've already got a reasonably capable constraint
system that'll handle long-running stable/unstable schemes along the
lines of GHC's? Hmm, that also suggests package aliases ala GHC-stable,
GHC-unstable might be useful too, though.

The current situation with Parsec is both odd and easy.

Philippa Cowderoy <flippa at flippac.org>

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