Peter Verswyvelen
So yes, without using IO, Haskell forces you into this safe spot
One could argue that IO should be broken down into a set of "sub-monads" encapsulating various subsets of the functionality - file system, network access, randomness, and so on. This could extend the "safe spot" to cover much more computational real estate, and effectively sandbox programs in various ways. So instead of 'main :: IO ()', a text processing program using stdin and stdout could have type 'main :: MonadStdIO m => m ()'. For testing, you could then define your own monad implementing 'putStrLn' and 'readLn' etc, and a function 'runStdIO :: MonadStdIO m => m () -> String' that you are free to use in your quickcheck properties. (ObAttribution: I think it was a posting by Lennart Augustsson on unique names that brought this to my mind, but a quick googling didn't find that exact mail.) -k -- If I haven't seen further, it is by standing in the footprints of giants