We've had a SICP discussion/reading group running for a few months. [Sundays at 3pm Pacific]
Currently we are looking at §4.4 — Logic Programming. [0]
Includes the book's stream based implementation of a pattern-matcher and unification (properly in scheme).
Looking at connections to Hindley–Milner.
see also: miniKanren, The Reasoned Schemer, @will_byrd
[0]: https://sarabander.github.io/sicp/html/4_002e4.xhtml#g_t4_00...