Mercurial > 12ws.info2
view exercises/src/Queue.hs @ 30:8bf7ca2663d2
Advanced AdditionParser
author | Markus Kaiser <markus.kaiser@in.tum.de> |
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date | Sat, 12 Jan 2013 14:36:43 +0000 |
parents | ea3fba2381bc |
children |
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module Queue (Queue, empty, isEmpty, enqueue, dequeue) where import Test.QuickCheck import Test.QuickCheck.Poly (A) newtype Queue a = Queue [a] deriving (Eq, Show) empty :: Queue a empty = Queue [] isEmpty :: Queue a -> Bool isEmpty (Queue []) = True isEmpty _ = False enqueue :: a -> Queue a -> Queue a enqueue x (Queue xs) = Queue (xs ++ [x]) dequeue :: Queue a -> (a, Queue a) dequeue (Queue (x : xs)) = (x, Queue xs) toList :: Queue a -> [a] toList (Queue xs) = xs {- QuickCheck Tests -} instance Arbitrary a => Arbitrary (Queue a) where arbitrary = do xs <- arbitrary return $ Queue xs prop_isEmpty_empty = isEmpty empty prop_isEmpty_enqueue x q = not (isEmpty (enqueue (x :: A) q)) prop_toList_enqueue x q = toList (enqueue x q) == toList q ++ [x :: A] prop_toList_dequeue x q = not (isEmpty q) ==> (x :: A) : toList q' == toList q where (x, q') = dequeue q prop_toList_ext q q' = toList q == toList q' ==> (q :: Queue A) == q'