On Fri, Jan 21, 2011 at 7:52 PM, Daryoush Mehrtash <dmehrtash@gmail.com> wrote:

loop = MonadPlus m => m Bool
loop = loop

If we apply Just to loop as follows

test2 :: MonadPlus m => m (Maybe Bool)
test2 = loop >>= return . Just

the evaluation of test2 does not terminate because >>= has to evaluate loop. But this does not correctly reflect the behaviour in a functional logic language like Curry. For example, if you have a function that checks whether the outermost constructor of test2 is Just, the test is supposed to be successful. In the naive model for non-determinism this is not the case.

Do I have to have MonadPlus m or would any other Monad class work the same way?

I'm afraid, I don't quite get you question. Would you mind clarifying it with an example?

Also, Jan, I don't understand your comment about continuation monads. Maybe I am a bit numb today.. What property do you mean do continuation monads have or not?

Thanks,

Sebastian