Sebastiaan Visser
Suppose I have a list of IO computations that depends on a few very time consuming pure operations. The pure operations are not dependent on the real world:
computation :: [IO Int] computation = [ smallIOfunc timeConsumingPureOperation0 , smallIOfunc timeConsumingPureOperation1 , smallIOfunc timeConsumingPureOperation2 , smallIOfunc timeConsumingPureOperation3 ] where smallIOfunc a = print a >> return a
I take it that, because you "do not really have the control to change things `deep' inside the code", it is not an option to redefine computation = [ smallIOfunc x0 , smallIOfunc x1 , smallIOfunc x2 , smallIOfunc x3 ] where smallIOfunc a = print a >> return a x0 = timeConsumingPureOperation0 x1 = timeConsumingPureOperation1 x2 = timeConsumingPureOperation2 x3 = timeConsumingPureOperation3 Can you define smallIOfunc to be more polymorphic in the monad? That is, can you define a class of monads (MonadBehavior, let's call it) that contains member functions for operations (such as print) you want to perform in smallIOfunc, then write smallIOfunc to be polymorphic over such a monad? If so, you can then implement two instances of this class: one for IO and one for a term representation of behavior. -- Edit this signature at http://www.digitas.harvard.edu/cgi-bin/ken/sig Who would have thought LISP would come back to life. Steve Bourne, in an interview about Bourne Shell.