Hello, I would like to announce the release of HFlags, a command line flags library that makes it very easy to define and use flags. The API is similar to Google's gflags, here is a very simple example program: -=- #!/usr/bin/env runhaskell {-# LANGUAGE TemplateHaskell #-} import HFlags defineFlag "name" "Indiana Jones" "Who to greet." defineFlag "r:repeat" (3 + 4 :: Int) "Number of times to repeat the message." main = do remainingArgs <- $(initHFlags "Simple program v0.1") sequence_ $ replicate flags_repeat greet where greet = putStrLn $ "Hello " ++ flags_name ++ ", very nice to meet you!" -=- As you can see, we have TemplateHaskell functions to help with the definition (and initialization) of the flags, and the values themselves are pure, no need for being in the IO monad to use the value of the flags. Also, the initHFlags function automagically gathers all the flags defined anywhere in the whole program, so if a library defines flags, you don't have to mention it in the main, but the user will still be able to set those flags too. More details behind this design and more example can be found in the following post: http://blog.risko.hu/2012/04/ann-hflags-0.html Comments and criticism is welcome. Code: http://github.com/errge/hflags Examples: https://github.com/errge/hflags/tree/master/examples Hackage: http://hackage.haskell.org/package/hflags Best regards, Gergely Risko