[Haskell-cafe] Parsec 3 Description

Duncan Coutts duncan.coutts at worc.ox.ac.uk
Thu Sep 4 16:38:42 EDT 2008

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.


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