PAPaulHoule·Aug 24, 2023
I've met a few young programmers who heard somewhere that object-oriented programming was bad and they want to get the enlightenment of functional programming that they've heard about. Frequently they travel from job to job like itinerant martial artists always looking for somewhere where they practice the true technique but they always seem disappointed as it is just as easy if not easier to screw up handling errors with monads than it is with exceptions and they find analogies like "a monad is like a burrito" just get them more confused.
As for something profound I'd point you to
https://github.com/cerner/clara-rules
which many people will struggle with because like many other production rules engines in LISP (and many other examples of simple compilers), there is hardly any code! Contrast that to the orders of magnitude larger rules
Read the rest
engine Drools
https://github.com/kiegroup/drools
which is so crazy-complicated primarily because the Drools language is Java-based so you need all sorts of things that Clara or CLIPS don't need. Note that both of these systems use variations of this algorithm
https://en.wikipedia.org/wiki/Rete_algorithm
where a set of rules can be compiled to a network of transitions that can happen when facts are added to the knowledge base so it is very much an example of compiler technology. (That said, Drools supports a lot of features that Clara doesn't and also supports a very advanced RETE-like algorithm that can exploit parallelism that early versions couldn't.)