[Haskell-cafe] Help mixing pure and IO code

2009-11-29 Thread papa . eric
Hi haskell helpers, Learning haskell, I wanted to explore how to write pure code and then add some IO on top of it, keeping the main code pure. The idea was to write a very simple two-player game, then define some strategies to play it that do not involve IO, and finally use strategies involving R

Re: [Haskell-cafe] GHCi infers a type but refuses it as type signature

2009-06-24 Thread papa . eric
> That depends on the monad library. In transformers it would be: > > (Monad m, Eq a) => a -> StateT [a] m Bool > > State s is just a type synonym for StateT s Identity, so this works for State > as well. I like it, it is simpler than the one using MonadState. I had read many tutorials and wi

Re: [Haskell-cafe] GHCi infers a type but refuses it as type signature

2009-06-23 Thread papa . eric
> Simple: the definition of MonadState uses those extensions. Thanks, yes it helps and explains all. :^) I suppose then that if -XFlexibleContexts is indeed required by the standard libraries, it is a "safe" extension, meaning supported by all compilers? Are many such extensions de-facto standa