[Haskell-cafe] Are constructors strict?

Daryoush Mehrtash dmehrtash at gmail.com
Fri Jan 21 11:52:41 CET 2011

>  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


Weblog:  http://perlustration.blogspot.com/
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