On Wed, 2006-10-25 at 09:39 -0500, Brian Smith wrote:

>     Name: foo
>     Version: 1.0
>
>     configuration: flag(debug)
>     Name: foo-debug
>
> Otherwise, how can I have a debug and an optimized configuration of a
> given library installed at the same time?

You can't. No current Haskell implementation supports this (without
doing things manually like using separate package databases / search
paths).

What you want is what the ghc build system refers to as a 'way'. It's a
whole other discussion I think.

Yes, I am interested in building with different "ways" as you say. But, I think one of your examples used -DDEBUG. I think it is reasonable to want to install regular and debug versions of a package together.

You said that no current Haskell implementation supports what I proposed. But, isn't this purely a Cabal issue. If I give a -debug flag to Cabal, and Cabal allows me to rename the package to foo-debug (by allowing me to put a name entry in the configuration stanza, like in my example), then foo and foo-debug can sit right next to each other in GHC or Hugs (at least). The user would do:

     runhaskell Setup.lhs configure -debug
     runhaskell Setup.lhs build
     runhaskell Setup.lhs install

Now, foo-debug is installed. Then:

     runhaskell Setup.lhs configure
     runhaskell Setup.lhs build
     runhaskell Setup.lhs install

Now, foo is installed too. Then, we can make packages that depend on either foo or foo-debug using the mechanism you proposed.

     Configuration: flag(debug)
     Name: bar-debug
     Build-depends: foo-debug || foo

     Configuration: !flag(debug)
     Name: bar
     Build-depends: foo

The only extension to your idea is being able to change the name of the installed package in the configuration. I think that this is a very desirable feature because it allows people to build packages with names that uniquely identify the configuration, if the choose to do so.

Regards,
Brian