[WaxProlix]

Anyone know of an online reference with this sort of material? Not huge on book collecting these days, and freer is better.

[jlarocco]

Oksaki's thesis, the basis for the book, is available online for free:

http://www.cs.cmu.edu/~rwh/theses/okasaki.pdf

The book itself is available on Kindle.

[WaxProlix]

Awesome.

[luddypants]

Top result in Bing/Google is a pdf. Not sure if it's a pre-print edition, looks like a PhD thesis.

[maemre]

IIRC, it was originally Okasaki's PhD thesis, then he converted it into a book.

edit: source: http://www.usma.edu/eecs/SitePages/Chris%20Okasaki.aspx#cup9...

[fiatmoney]

The Clojure source code for its data structures.

[jacksontale]

I think its SML in the book