    [StackSet.hs: (peek): why use return when you just mean Just?  it
    will just confuse the n00bs and return to haunt you later.  Brent
    Yorgey <byorgey@gmail.com>**20071022190732] {
    hunk ./StackSet.hs 314
    -peek = with Nothing (return . focus)
    +peek = with Nothing (Just . focus)
    }

I used return . focus here because it reads nicely :)
After all, peek returns focus..

Ah. Well, you can keep it if you really want. =) It's just that I had to stare at it for a while to convince myself that I understood what it was doing. Especially in juxtaposition with the previous function (which has (Just . f)), it made me think, "wait, hmm, there must be a good reason that this one uses return but the one above uses Just..." It took me a while to realize that no, there really wasn't.

-Brent