While I'm at (free) books: a great example implementation of unification (in Lisp) is in chapter 11 "Logic Programming" of Peter Norvig's "Paradigms of Artifici

While I'm at (free) books: a great example implementation of unification (in Lisp) is in chapter 11 "Logic Programming" of Peter Norvig's "Paradigms of Artificial Intelligence Programming: Case Studies in Common Lisp". https://github.com/norvig/paip-lisp https://github.com/norvig/paip-lisp There is also an implementation in Python, but I have never tested it, just googled it now: https://github.com/dhconnelly/paip-python/blob/master/prolog.py https://github.com/dhconnelly/paip-python/blob/master/prolog... https://dhconnelly.github.io/paip-python/docs/prolog.html https://dhconnelly.github.io/paip-python/docs/prolog.html