Re: [Haskell-beginners] Disappearing Module Problem

On Mon, Sep 12, 2011 at 3:54 PM, Michael Craig wrote:

I was using "cabal install aeson" and "cabal install http-enumerator". Running the combined command fixed the issue. I'd forgotten that cabal allows for it. Is this necessary because of mutual dependencies? With the Platform installation of cabal, I could run cabal install for each package and everything would work fine. What's the difference?

What happens is that when you run "cabal install" with multiple arguments, the dependency resolver tries to come up with an install plan that jointly satisfies the dependencies of all arguments. When you do the installs one at a time it is possible in some cases to break already installed packages. One way to check for this is to use the 'ghc-pks' command to look for broken packages. Antoine

Best, Mike S Craig (908) 328 8030

On Mon, Sep 12, 2011 at 4:46 PM, Antoine Latter wrote:

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On Mon, Sep 12, 2011 at 3:34 PM, Michael Craig wrote:

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I'm trying to install aeson and http-enumerator on an otherwise fresh installation of ghc 7.2 on OS X 10.7. I was inspired by beastaugh's gist on getting cabal-install running on Lion: https://gist.github.com/1169332. I can install either aeson or http-enumerator and it'll work fine. However, as soon as I install the second one the first one disappears. The files are all there in .cabal/lib, but ghc can't find the module. Any ideas?

What command are you using to install these, specifically?

What does the following do:

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cabal install aeson http-enumerator

Thanks, Antoine

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Mike S Craig

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