Cabal constraint solver

[Christian Höner zu Siederdissen]

Hi,

thanks to you all for the answers. I will then go with increasing the
version number for testing, this seems to be the easiest way to go.

And indeed, 'cabal unpack' fetches ( ;-) ) the package without checking
that constraints are met.

Gruss,
Christian

* Christian Höner zu Siederdissen <choener at tbi.univie.ac.at> [03.10.2010 00:07]:
> Hi,
> 
> does the Cabal constraint solver always try to solve the complete graph?
> 
> example: (ghc-7.0.0-rc1)
> 
> $ cabal install parsec-3.1.0
> cabal: cannot configure syb-0.2.1. It requires base >=4.0 && <4.3
> 
> cd syb-0.2.1
> * remove base<4.3 constraint from syb.cabal
> cabal install
> * syb-0.2.1 is now installed and works!
> 
> $ cabal install parsec-3.1.0
> cabal: cannot configure syb-0.2.1. It requires base >=4.0 && <4.3
> 
> 
> 
> This is rather annoying: the constraint is solved (eg. syb is installed)
> but we /still/ assume that we can not continue. So obviously, I would
> like to be able to have cabal assume constraints fullfilled if the
> package is installed.
> 
> Am I missing something? (Otherwise, testing packages with 7-rc1 is
> becoming annoying as almost everything depends on syb)
> 
> ===
> 
> And a second thing: cabal fetch
> How does one disable the solver for fetching packages? It is a bit
> annoying (here too) that 'cabal fetch parsec-3.1.0' fails. (It should
> maybe warn that constraints can not be fulfilled but the idea here is to
> get the packages to change them manually)
> 
> ===
> 
> So did I miss anything or can I write a bug report? ;-)
> 
> 
> 
> Gruss,
> Christian
> 



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