[Haskell-cafe] Hackage dependencies problem.

Albert Y. C. Lai trebla at vex.net
Mon Nov 19 20:47:40 CET 2012

On 12-11-19 04:45 AM, Ivan Lazar Miljenovic wrote:
> On 19 November 2012 18:21, Magicloud Magiclouds
> <magicloud.magiclouds at gmail.com> wrote:
>> <command line>: cannot satisfy -package Cabal-1.16.0:
>>      Cabal-1.16.0-dd0ce1db6fea670a788547ee85411486 is unusable due to missing
>> or recursive dependencies:
>>        directory-
>> process-
>> unix-
>>      (use -v for more information)
>>    What should I do? Why user space directory and process would interrupt
>> Cabal in global space?
> It shouldn't.
> Can you please give an example of a package that gives you an error like this?
> Also, what does "ghc-pkg check" say?
> The only thing I can think of is that you're trying to upgrade a
> package like array, containers, etc.

It does. It has always been. When unioning user and global, user takes 
precedence: user directory- shadows global directory- (GHC 
User's Guide 4.9.4). But look closer: user directory- 
shadows global directory- Therefore, if global 
Cabal-1.16.0 was built against directory-, it's a 
missing dependency for you.

See my http://www.vex.net/~trebla/haskell/sicp.xhtml#pigeon

Fortunately, shadowing is a sessional property, not a data-loss 
property. One can say, it's a data-surplus property. To regain working 
sessions, cut surplus data, add -no-user-package-db to all your ghc and 
ghci commands.

"ghc-pkg check" does not report shadowing. Go straight for "ghc -v".

This is what you get for "--reinstall".

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