On Sun, Dec 22, 2013 at 02:38:53PM +0000, harry wrote:

Is there any simple way for a program to retrieve a list of installed packages (such as ghc-pkg list returns), or would it be easier to execute phc-pkg as an external process and catch the output?

Try the hackage-db package: http://hackage.haskell.org/package/hackage%2Ddb -Brent