Yes! I originally mentioned that, but it didn't really fit and I cut it. Okasaki's _Purely Functional Data Structures_ uses SML to describe a variety of "purel

Yes! I originally mentioned that, but it didn't really fit and I cut it. Okasaki's _Purely Functional Data Structures_ uses SML to describe a variety of "purely functional" data structures, most of which are immutable, persistent, and exploit laziness for amortized performance guarantees. (There's an appendix with Haskell versions.)