Libraries Digest, Vol 87, Issue 16

Duncan Coutts duncan.coutts at
Wed Nov 10 10:25:11 EST 2010

On 10 November 2010 10:31, John Lato <jwlato at> wrote:

>> > If cabal supported something like run-time-specified repos it would be
>> > much simpler.
>> What sort of thing are you thinking of here?
> If, in addition to the global and user package stores, you could specify
> alternate package stores.  Then it would be possible to do e.g.
> cabal install --use-package-store=./buildlibs
> to create a package store at ./buildlibs (if it doesn't exist) and install a
> library there.  Then later commands could do
> cabal install --extra-package-store=./buildlibs
> to check for packages in that extra location in addition to the default
> global and user locations.

Yes, this is already implemented. There is a single --package-db flag
for both purposes.

> This would certainly enable building non-blessed libs as part of the HP and
> differentiating from the normal blessed packages.  It might be useful for
> other reasons too.  I'm not saying it's a good idea for HP, just that it
> would be technically possible.
> Were some other people already talking about this in this thread?

The issue is with distro packages. We encourage distros to package
individual cabal packages as individual native distro packages. Many
distros have developed automated tools that perform this translation.
If we have "hidden" or non-installed package dependencies then it
complicates this model. Distros would then need to change their tools
to allow bundling multiple cabal libs into a single program package.


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