elemTree :: Eq a => a -> Tree a -> Bool
elemTree e tree = or $ map (==e) $ runOmega $ flatten tree
flatten Nil = fail ""
flatten (Branch l a r) = return a `Monad.mplus` flatten l `Monad.mplus` flatten r
Действительно, совсем переставлять порядок в flatten (BRanch ...) не получается. flatten l `mplus` return a `mplus` flatten r не работает.
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Date: 2011-12-21 10:59 pm (UTC)