> > data Stack a = EmptyStk | Stk a (Stack a)
I find it amusing that the book defined a type that is exactly isomorphic to the standard list (EmptyStk === [] and Stk === (:)). I guess it's just for clarity? On Thu, Feb 4, 2010 at 12:29 PM, Casey Hawthorne <cas...@istar.ca> wrote: > On Thu, 4 Feb 2010 09:07:28 -0800 (PST), you wrote: > > >Can't find a Stack datatype on Hoogle? Where should I look? > > > >Michael > > > > > From "Algorithms: a functional programming approach" > Second edition > Fethi Rabhi > Guy Lapalme > > > data Stack a = EmptyStk > | > Stk a (Stack a) > > push x s = Stk x s > > pop EmptyStk = error "pop from an empty stack" > pop (Stk _ s) = s > > top EmptyStk = error "top from an empty stack" > top (Stk x _) = x > > emptyStack = EmptyStk > > stackEmpty EmptyStk = True > stackEmpty _ = False > > > > > newtype Stack a = Stk [a] > > push x (Stk xs) = Stk (x:xs) > > pop (Stk []) = error "pop from an empty stack" > pop (Stk (_:xs)) = Stk xs > > top (Stk []) = error "top from an empty stack" > top (Stk (x:_)) = x > > emptyStack = Stk [] > > stackEmpty (Stk []) = True > stackEmpty (Stk _ ) = False > > > -- > Regards, > Casey > _______________________________________________ > Haskell-Cafe mailing list > Haskell-Cafe@haskell.org > http://www.haskell.org/mailman/listinfo/haskell-cafe >
_______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
