PG does indeed use a lot of mutation in his Arc code. "Karma" on `vote-for` on HN is just incremented like this: (++ (karma i!by) (case dir up 1 down -1))

PG does indeed use a lot of mutation in his Arc code. "Karma" on `vote-for` on HN is just incremented like this: (++ (karma i!by) (case dir up 1 down -1)) At first this looks nice and simple, but when you have to write `unvote`, you're in trouble (because not all votes increase karma, and you'll have to figure out whether the particular vote being unvoted did). I was reading through The Reasoned Schemer (which covers MiniKanren). They do a lot of unnesting when translating from functional to logical programming. And yes, this does introduce an additional variable each time, making the logical version slightly longer. Apart from the `markdown` in the Hacker News code, there is an `unmarkdown` function[0] (whose job is to translate back from HTML to markdown!). In Prolog you could have gotten away with one predicate for that. That's a 50% saving just there. And you could perhaps use DCGs to cut it down further. Not sure I about Prolog being mostly first order. Plenty of built-in predicates that take predicate arguments, like `maplist`, `findall` and `foldl` that seem to be as commonly used as in Lisp. You might be right about lambdas missing though, so not sure you can emit a predicate (although you could emit the name of a predicate and call it). I'm too new to Prolog to tell, really. [0]: https://github.com/arclanguage/anarki/blob/master/lib/markdown.arc#L120 https://github.com/arclanguage/anarki/blob/master/lib/markdo...