author | haftmann |
Wed, 15 Dec 2010 10:06:36 +0100 | |
changeset 41185 | d5f0e556ffd3 |
parent 39210 | 985b13c5a61d |
child 44970 | 52f809bc5402 |
permissions | -rw-r--r-- |
{-# LANGUAGE ScopedTypeVariables #-} module Example where { data Queue a = AQueue [a] [a]; empty :: forall a. Queue a; empty = AQueue [] []; dequeue :: forall a. Queue a -> (Maybe a, Queue a); dequeue (AQueue [] []) = (Nothing, AQueue [] []); dequeue (AQueue xs (y : ys)) = (Just y, AQueue xs ys); dequeue (AQueue (v : va) []) = let { (y : ys) = reverse (v : va); } in (Just y, AQueue [] ys); enqueue :: forall a. a -> Queue a -> Queue a; enqueue x (AQueue xs ys) = AQueue (x : xs) ys; }