Question

I’m trying to install a package (nymphaea as it happens). This depends on an earlier version of base than the one I have. I’m not keen on downgrading my base libraries, so I’d like to try to just ignore that dependency, and see how things go.

Is there a way to tell cabal to miss out a particular dependency?

Update: After I edit the cabal file, what do I do with it? Cabal doesn’t have an obvious way to point it at a file, nor anywhere I can manually put cabal files, as far as I can tell.

[As per below, apparently I should just invoke cabal install in a directory containing the edited cabal file ]

Update 2: Unfortunately, cabal gives me a weird error about package versions being required which I appear to have:

$ cabal install -v --upgrade-dependencies time
Reading available packages...
Resolving dependencies...
In order, the following would be installed:
time-1.2.0.5 (new version)
Extracting
C:\Users\Marcin\AppData\Roaming\cabal\packages\hackage.haskell.org\time\1.2.0.5\time-1.2.0.5.tar.gz
to C:\Users\Marcin\time-1.2.0.54736...
Creating C:\Users\Marcin\time-1.2.0.54736\time-1.2.0.5\dist\setup (and its
parents)
C:\Program Files (x86)\Haskell Platform\2011.2.0.1\bin\ghc.exe --make C:\Users\Marcin\time-1.2.0.54736\time-1.2.0.5\Setu
p.hs -o C:\Users\Marcin\time-1.2.0.54736\time-1.2.0.5\dist\setup\setup.exe -odir C:\Users\Marcin\time-1.2.0.54736\time-1
.2.0.5\dist\setup -hidir C:\Users\Marcin\time-1.2.0.54736\time-1.2.0.5\dist\setup -i -iC:\Users\Marcin\time-1.2.0.54736\
time-1.2.0.5 -package Cabal-1.10.1.0
<command line>: cannot satisfy -package Cabal-1.10.1.0:
    Cabal-1.10.1.0-55f781465ee9f32289755ad706c71f0f is unusable due to missing or recursive dependencies:
      directory-1.1.0.0-3a2367d72569467a8af8a231656ff1b8 process-1.0.1.5-b3dded8e54a2e13d22af410bdcfafff4
    (use -v for more information)
World file is already up to date.
cabal.exe: Error: some packages failed to install:
time-1.2.0.5 failed during the configure step. The exception was:
ExitFailure 1

Answer 1

To follow up on the comments to Don’s answer:

First, grab the package from Hackage.

$ cabal unpack nymphaea

Then edit the .cabal file and change base <= 4.1.0.0 to base > 3 && < 5.

$ cd nymphaea-0.3
$ vim nymphaea.cabal

Now, try to install it.

$ cabal install

I got it to work with this change using Haskell Platform 2011.2.0.1 on Ubuntu Natty after installing the required Debian packages.