FYI, I found the OP while re-reading Norvig's classic on spell-checker design, in which he mentions the chapter in passing: http://norvig.com/spell-correct.html
The chapter is part of a book, Beautiful Data, and Norvig has a separate page for the source code:
Fun fact: the edits function in the newer chapter doesn't find quite the same edits as the older spelling corrector. (I found one or two differences in testing on /usr/share/dict/words -- originally with the code I'm acknowledged for at the end, but I think I checked it was still there in the chapter's version of the code. But since the difference is so rare and correctness is probabilistic anyway, it's kind of nitpicky to call it a bug.)