It is also possible to refer to a package explicitly durring import with the PackageImports language pragma. You can read about it in the ghc manual[1]. Patrick [1] http://www.haskell.org/ghc/docs/7.2.1/html/users_guide/syntax-extns.html#pac... On Fri, Apr 26, 2013 at 10:10 PM, Hong Yang wrote:

Thanks.

On Fri, Apr 26, 2013 at 8:33 AM, Brandon Allbery wrote:

...

On Thu, Apr 25, 2013 at 11:12 PM, Hong Yang wrote:

...

There are two modules called the same name: System.IO.Strict, documented respectively at

http://hackage.haskell.org/packages/archive/strict-io/0.2.1/doc/html/System-... http://hackage.haskell.org/package/strict-0.3.2

My questions are:

1) Will these two modules coexist in the same version of GHC? Or put it another way, both modules' .tar.gz files have System/IO/Strict.hs inside, will they overlap in physical disk? From where can I tell which locations they will be installed to?

Each module gets its own directory tree under /usr/lib/ghc or ~/.ghc.

...

2) If yes, which module will "import System.IO.Strict" actually use?

This is a bit harder; it will try to pick one, but I don't know the rules. Ultimately it's best to use -package parameters to tell it which package to take it from.

This is where building with cabal-install helps, as you specify the package to use in the manifest and only the packages listed in the manifest will be visible to ghc.

-- brandon s allbery kf8nh sine nomine associates allbery.b@gmail.com ballbery@sinenomine.net unix, openafs, kerberos, infrastructure, xmonad http://sinenomine.net

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