Jacek Generowicz wrote:
# Imagine an activity which may be performed either by a computer, or # by a human (alternatively, either locally, or remotely across a # network). From Haskell's type system's perspective, these two will # look completely different (most obviously, the human (or the # network) is wrapped in IO). How can they be made interchangeable ?
# To demonstrate what I mean, I offer the following concrete toy # example, in Python.
# It's a harness for playing the trivial higher-lower number guessing # game, with interchangeable strategies for either player. In this # example I provide two strategies (Computer / ask Human via IO) for # each role (asker and guesser).
# How can this sort of interchangeability of computations which are # conceptually identical, but incompatible from the types perspective, # be expressed in Haskell?
Have a look at my operational package, in particular the TicTacToe.hs example on the examples page. http://hackage.haskell.org/package/operational (Unfortunately, the haskell.org domain is seized at the moment, so this link won't work for a while. Also, please yell if you can't find the examples page once the link works again.) Regards, Heinrich Apfelmus -- http://apfelmus.nfshost.com