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34 lines
580 B
Plaintext
34 lines
580 B
Plaintext
implementation module stack
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import StdEnv
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:: Stack a :== [a]
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newStack :: (Stack a)
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newStack = []
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push :: a (Stack a) -> Stack a
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push x s = [x:s]
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pushes :: [a] (Stack a) -> Stack a
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pushes x s = x ++ s
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pop :: (Stack a) -> Stack a
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pop [] = abort "Cannot use pop on an empty stack"
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pop [e:s] = s
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popn :: Int (Stack a) -> Stack a
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popn n s = drop n s
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top :: (Stack a) -> a
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top [] = abort "Cannot use top on an empty stack"
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top [e:s] = e
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topn :: Int (Stack a) -> [a]
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topn n s = take n s
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elements :: (Stack a) -> [a]
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elements s = s
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count :: (Stack a) -> Int
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count s = length s
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