[Haskell-cafe] Looking for feedback on my attempt at a tree construction edsl

[Stephen Tetley]

Andy Gill uses a monad in his Dot library to allow graphs to have
references as they are built. It's a pattern I like a lot and has been
very useful for my graphics kit Wumpus.

That said, while it's a good technique for graphs, its use is more
equivocal for trees where nesting is more prominent. I use a reference
monad for tree building/drawing at the moment (references are
essential) but I'd switch to a technique that is better with nesting
if I could think of one.

At the moment the Tree EDSL doesn't use references, so I'd "third" the
notion that the code would be simpler if it was pure.