John Lusk
I have not, but I might. This was a little work project that I've now run out of time for.
I was really hoping for a deeper discussion of state management than "just use this package." This seems kind of like receiving a stream of inputs from a user and needing to keep track of several items of state that are changing independently (as opposed to the neat problems usually used in basic FP education).
Should I be taking a more monadic approach?
Well, we have to start somewhere :) Anyway, you don't necessarily have to resort to the state monad. I believe, based you your other code that you quite easily can go from your list of lines to a list of `(Int, String)`, where the integer indicates the indentation level. Then you can look at `Data.Tree` (in containers) and `Data.Tree.Zipper` (in rosezipper) to build your tree. This is my quick hack: ~~~ buildTree _ zipPos [] = zipPos buildTree n zipPos xx@((lvl, s):xs) | lvl > n = let newZipPos = children zipPos node = Node s [] in buildTree lvl (insert node newZipPos) xs | lvl == n = let newZipPos = nextSpace zipPos node = Node s [] in buildTree lvl (insert node newZipPos) xs | lvl < n = let (Just newZipPos) = parent zipPos in buildTree (n - 1) newZipPos xx ~~~ With the following definitions in place: ~~~ ils = [ (1, "The root") , (2, "Child 1") , (3, "Child 1.1") , (4, "Child 1.1.1") , (3, "Child 1.2") , (2, "Child 2") ] zipRoot = fromTree $ Node "absolute top" [] ~~~ I build the tree, and print it, like this: ~~~ putStrLn $ drawTree $ toTree $ buildTree 0 zipRoot ils top | `- The root | +- Child 1 | | | +- Child 1.1 | | | | | `- Child 1.1.1 | | | `- Child 1.2 | `- Child 2 ~~~ Whether this is usable for you depends a lot on how big your logs are, I suppose. If this was something that I'd keep around for a while I'd probably look into rewriting `buildTree` so that it would fit for use with `mapAccumL`. /M -- Magnus Therning OpenPGP: 0x927912051716CE39 email: magnus@therning.org jabber: magnus@therning.org twitter: magthe http://therning.org/magnus The British have "the perfect temperament to be hackers—technically skilled, slightly disrespectful of authority, and just a touch of criminal behavior". — Mary Ann Davidson, Oracle's Security Chief