ref: d5ce41f05bc322fa2fb4d0eee66080b3b3004853
parent: 9799fbd9e8c7fd186365c628bf2024d458dafc75
author: Peter Mikkelsen <peter@pmikkelsen.com>
date: Tue Jun 29 20:07:49 EDT 2021
Start work on an evaluator. For now it knows how to unify but doesn't know how to handle builtin predicates or how to backtrack