Thanks this is exactly what I need, should make coding in functional languages a lot more readable. Actually it appears GHC supports the use of unicode characters for operators via packages and an extension[1], if it wasn't for your post I would not have discovered this, cheers!
I wouldn't recommend using that one. There is a newer plugin [1] that uses "after" in combination with conceal syntax to achieve the same effect but without buffer hacks on load/save.
Haskell-Conceal also works a lot better than unicode-haskell: it doesn't erroneously turn "\n" into "λn", and it replaces :: with a single-glyph equivalent so that signature and definition line up nicely.
Having said that, I still prefer <- and -> to ← and →, at least on screen: those Unicode arrowheads are too small on all the fixed-width fonts I've ever seen.
Seems I should've refreshed before posting (now deleted)! As you can see from the plugin file, applying the maps isn't all that complicated, though it certainly would be nice to have it built in. I'm not an emacs user, but I seem to recall using this feature before... anyone know if TextMate had this implemented?
[1]: https://github.com/frerich/unicode-haskell