Re: [Haskell-cafe] Painting logs to get a coloured tree

2009/2/9 Joachim Breitner

Now while this works, and while ST is still somewhat pure, I'm wondering if there is no better way of expressing "This piece of information came from the point in a data structure, so something else can be put here easily".

You might want to look into zippers: http://haskell.org/haskellwiki/Zipper Luke