Why in 2020 should I learn Prolog?

>> Learning any language in enough depth will take time away from learning something else. So you need to figure out your priorities first.

> I doubt that will hold. In my understanding (but I might be wrong) this has been disproved for natural languages, i.e., (most) children learning more natural languages do not perform worse on their mother tongue except for a brief period were they tend to mix languages.

> Likewise, learning Prolog provides you with a different perspective on programming that, once understood, can be applied to other languages as well. For example, I tend to put a lot of “knowledge” in data structures and use a small program using this data to do the job rather than using endless if-then-else, also when programming in C or JavaScript (my main imperative languages).

I'm reminded of Richard O'Keefe's comment, in the context about a decision about which PLs to teach in 1992, "Rob Hagan at Monash had shown that you could teach students more COBOL with one semester of Scheme and one semester of COBOL than you could with three semesters of COBOL."

https://news.ycombinator.com/item?id=28337973

As a language (at least SWI-Prolog), it's missing some niceties that I took for granted: e.g., a function's output is always to a C-style output variable, all "context" variables must be passed around in recursive calls, etc.

There are several well-regarded books on Prolog that also feel quite antiquated in their concerns: authors taking pains to build elaborate conventions around function naming and argument ordering, etc.

Aside from its unusual features, Prolog really feels like a language from the early 90s, with a small, static standard library you might memorize, and authors offering "helpful tips" around functions with slightly different names in "commercial systems."

- because you need it,

- because you want it.