Very interesting article! I like the fact that you mentioned Prolog as one of the less mainstream languages to learn. During my time at uni I found that both Haskell and Prolog really changed the way I approached different problems and gave me a high level perspective to problem solving. Some interesting resources to learn Prolog:
I did some Prolog programming too for fun, and boy! it requires a complete paradigm shift in thinking! For those unfamiliar with Prolog, Prolog is very different from procedural programing languages. In procedural languages like C and Python, we assign values to variables and ask the computer to do operations on them. In logical programming langauges like Prolog and LISP, we tell the computer truth values of a list of statements, and ask the computer to check truth values of other statements using the provided list.
In the past, Prolog and LISP aimed to become the go to language for Artificial Intelligence programming. Sadly, not many people use them any more.
(Common) Lisp is a multi-paradign language. It doesn't have any specific logic programming features, no more than any other generic language. Some lisps tend to lean towards functional paradigm. EDIT: OK, maybe Lisps' symbol type helps a bit on logic or AI but there's no built-in resolution algorithm like in Prolog.
But Prolog is really something different. I only know some basic ideas but definitely want to dig deeper in the future.
I'd also add Elixir as an alternative to Erlang. Still a different way of thinking if you're an imperative programmer but has nice tools and perhaps a familiar syntax.
# http://www.swi-prolog.org/
# http://people.cs.kuleuven.be/~bart.demoen/PrologProgrammingC...
# http://www.cs.bham.ac.uk/~pjh/prolog_module/sem242.html
# http://www.learnprolognow.org/
I'm getting an itch now, I think I'll give Prolog a second go this new year.