[Haskell-cafe] Construct all possible trees

[Henning Thielemann]

On Thu, 14 Jun 2007, Tom Pledger wrote:

> *Andrew Coppin wrote:
> *
>
>  | I'm trying to construct a function
>  |
>  |   all_trees :: [Int] -> [Tree]
>  |
>  | such that all_trees [1,2,3] will yield
>  :
>
> If you write a helper function that takes an N element list, and returns
> all 2^N ways of dividing those elements into 2 lists, e.g.
>
>     splits "ab" --> [("ab",""),("b","a"),("a","b"),("","ab")]
>
> then you can use it both for dividing the initial list into kept and
> discarded elements, and for dividing a list between a left subtree and a
> right subtree.

This one was discussed recently:
 http://www.haskell.org/pipermail/haskell-cafe/2007-May/025767.html