Ask HN: What "exotic" language to learn?

I'm interested in learning a more exotic language for fun, and I'd like to hear some suggestions. Some I'm considering so far: Pascal, Lisp, Cobol, Fortran, Prolog, Forth, Ada, Erlang. Any others I should look at? Please no BF, lolcode and similar.

Honestly, if you haven't worked in assembly, learning it is actually really interesting.

Pascal is not exotic. It's one of the foundation languages that's been around for decades. If you want to learn top-down, structured programming, Pascal is easy to learn and a perfect language for small, quick one-person projects. (It's one of the first languages I learned, and the one I remember most fondly.)

Having worked professionally with Ada for decades, I can tell you quite unequivocally that it's not fun; not in the least. The only reason to learn Ada is if you want to work on huge projects with hundreds of other programmers for defense contractors.

I've never used Cobol but what little I know suggests that it may be even less fun than Ada.

If you want to bend your mind into new shapes, Prolog would be useful. You can do things with Prolog that are much more difficult than with other languages. Prolog lets you program using the backtracking paradigm, which is useful in solving some artificial intelligence problems.

If you want to learn functional programming, Lisp is often recommended, although I would probably suggest that the Racket dialect of Scheme is a better choice.

As far as the other languages go, Forth is usually used to program microcontrollers, Fortran for mathematics heavy applications, Erlang for multicore applications.

Assembly gets my vote too. Its one of the lowest level languages you can learn and it gives you a more 'wholesome' appreciation of computing.

Don't expect the ability to create something useful in it though.

I had much fun playing with Rebol