The reasons I've always heard for this is that 1.) It's so easy to define a tree and 2.) There are tons of different variations of trees and what you can do with them. Not that I 100% agree, just what I've always heard.
On Mon, Dec 1, 2008 at 6:09 AM, Christian Maeder <[EMAIL PROTECTED]>wrote: > Hi, > > I was surprised that I could not find a "classical" binary tree data > structure on hackage, mainly for teaching purposes, like: > > data BinTree a = Nil | Node (BinTree a) a (BinTree a) > > with a couple of utility functions and instances (i.e. in-order traversal). > > Surely, one may argue, that such a tree can always be defined on the fly > when needed, but nobody would argue so for lists or tuples. (Although > I've rarely seen someone redefining lists, it is quite common to > introduce user-defined products or enumerations.) > > There are rose trees in Data.Tree and many other variants of trees are > conceivable, ie. > > data Boom a = Leaf a | Node (Boom a) (Boom a) > > or a kind of combination: > > data BinLeafTree a b = > Leaf b > | Node (BinLeafTree a b) a (BinLeafTree a b) > > I don't know, why I find the above BinTree most important. I'm not even > sure if such a tree could be re-used for Search- or AVL-trees that need > strict fields with redundant size or height counters for efficiency > reasons. > > In any case I would find such a data type at least as useful as > http://hackage.haskell.org/cgi-bin/hackage-scripts/package/OneTuple > > Who would supply and maintain such a package? Or did I simply not search > hard enough? > > Cheers Christian > > P.S. I took the (non-empty) "Boom" from the Boom-Hierarchy described in > "An Exploration of the Bird-Meertens Formalism" by Roland Backhouse > 1988, Groningen > > _______________________________________________ > Libraries mailing list > [EMAIL PROTECTED] > http://www.haskell.org/mailman/listinfo/libraries >
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