On Fri, May 29, 2009 at 03:51:18PM +0300, Kari Pahula wrote:
> Hi. I upgraded Parsec to version 3.0.0 along with ghc 6.10.1. I got
> a bit of flak for doing that. Looks like there's a case for having
> 2.1.0.1 around, instead.
I did the same thing as with QuickCheck. The packages are introduced
as libghc6-parsec{2,3}-{dev,prof,doc}. haskell-parsec2 is the only
one providing libghc6-parsec-{dev,prof,doc}. They're still built with
the current haskell-devscripts, which treats different versions of
libraries with the same Cabal names poorly. You may need to ghc-pkg
expose them yourself.
It's a good idea to use
DEB_SETUP_GHC6_CONFIGURE_ARGS := --constraint='parsec<3'
if you're using hlibrary.mk. AFAIK 3.x's API is supposed to remain
backwards compatible, but its performance could still use more
profiling. Don't use 3.0.0 it if you don't need it. I don't know
where Parsec is going but there might be no reason to not use 3.x, at
some point. Or then not. Or perhaps GHC gets smart enough to make
identical code when the semantics match, making this issue moot. I've
seen people say that even Parsec 2.1 could have better performance.
In the meantime, I'm hoping that people are happy with this, having to
wait for NEW processing notwithstanding.
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