Dupont asked:
do you know Nomic?
It's a fabulous and strange game where you have the right to change the rules in the middle of the game!
I know nomic, but as has been pointed out, it's too wide-ranging to be captured in Haskell. So how about a game played in the Haskell type system where you get to play whatever type you like? Let's restrict ourselves to a total fragment of Haskell. Only allow structural recursion and that sort of thing. The 'board' is a Haskell type function. It'll look something like this: type Board a b c ... y z = ... with type variables a to z (no need to have precisely 26) and so that the right hand side is a type, not another type function. (A neutral third party will have to implement Board.) There are two players. They take turns where a turn consists of picking a concrete type to bind to precisely one previously unbound type variable. When there are no more legal moves left, player 1 now has to exhibit an element of the resulting type. If they succeed, they win, otherwise player 2 wins. Void is allowed. For example, consider type Board a b c d e f g = (Either a b, Either c d, Either e f, g) Player 1 must start by making g a type they know how to instantiate. Maybe g=Int. If not, then Player 2 chooses g=Void and they will never be able to make one of these 4-tuples. From now on, Player 2 has sente (to use go language) because Player 1 will always have to play in the same factor of the 4-tuple that Player 2 played in. Ultimately, however, Player 1 can force a win. -- Dan