Trie implementation

[ajb at spamcop.net]

G'day all.

Quoting Keith Wansbrough <Keith.Wansbrough at cl.cam.ac.uk>:

> Hi... I was writing some code yesterday to walk over a directory tree,
> and needed a Trie.  Not seeing one around, I wrote a basic
> implementation of the functions I needed (attached below).
>
> Has anyone else done this?  Should I polish it up and offer it for
> inclusion in Data?

Lots of people have. :-)

Here's mine, for the record:

http://cvs.sourceforge.net/viewcvs.py/hfl/hfl/edison/Assoc/TernaryTrie.hs?rev=1.18&view=auto

Cheers,
Andrew Bromage