In terms of implementation, though, it is far from simple. Lambda calculus has variables, which introduce huge complexity into the interpreter: especially if you want to do any kind of formal reasoning about programs, this complexity is a problem. We might want to reach for something even lower-level than lambda calculus: this is where combinator calculi come in.

This is a top-down introduction to core.logic which attempts to lead you to that elusive AHA! moment of understanding what logic programming is about.

Core miniKanren extends Scheme with three operations: ==, fresh, and conde. There is also run, which serves as an interface between Scheme and miniKanren, and whose value is a list.