[Haskell-cafe] Stack ADT?

michael rice nowgate at yahoo.com
Thu Feb 4 12:27:23 EST 2010

I was looking here: http://www.haskell.org/haskellwiki/Abstract_data_type

I haven't done much with modules so I'm guessing what you've provided is the guts of StackImpl, to hide the implementation?



--- On Thu, 2/4/10, Sebastian Fischer <sebf at informatik.uni-kiel.de> wrote:

From: Sebastian Fischer <sebf at informatik.uni-kiel.de>
Subject: Re: [Haskell-cafe] Stack ADT?
To: "haskell-cafe Cafe" <haskell-cafe at haskell.org>
Date: Thursday, February 4, 2010, 12:16 PM

On Feb 4, 2010, at 6:07 PM, michael rice wrote:

> Can't find a Stack datatype on Hoogle? Where should I look?

Could not find one on Hackage either. Probably because its so easy to handcraft your own:

    newtype Stack a = Stack [a]

    emptyStack = Stack []

    isEmptyStack (Stack xs) = null xs

    push x (Stack xs) = Stack (x:xs)

    pop (Stack (_:xs)) = Stack xs

    top (Stack (x:_)) = x

I saw such stacks in Haskell only for educational purposes. Usually, people seem to use lists directly.


--Underestimating the novelty of the future is a time-honored tradition.

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