Not well known but good programming languages?

>>60767492
brainfuck

++++++++++[>+++++++>++++++++++>+++>+<<<<-]>++.>+.+++++++..+++.>++.<<+++++++++++++++.>.+++.------.--------.>+.>.

If you are gonna learn programs you are never gonna use in industry for your own improvement, then the list is:
-Haskell
-ANSI Common Lisp
-Ada

If a programming language is good, it is already well known.
Don't get all fucking excited because you graduated Freshman CS.

>>60767492
>I want to learn some obscure one just for the fun of it.
For real fun, make your own, instead of learning someone else's.

>>60767492
https://en.wikipedia.org/wiki/ATS_(programming_language)
ATS has support for combining theorem proving with practical programming through the use of advanced type systems.
has demonstrated that the performance of ATS is comparable to that of the C and C++ programming languages.[2] By using theorem proving and strict type checking, the compiler can detect and prove that its implemented functions are not susceptible to bugs
by verifying pointer arithmetic and reference counting before the program compiles.

>>60767492
Any of the functional languages.SML, Ocaml, Haskell are the most prominent here.
There are some more advanced ones like ATS, Liquid Haskell, F*. They use some more advanced type theoretic stuff, if you like that.
Eff is a functional languages that has algebraic effects as a datatype which does things that are similar to monads in haskell but in a somewhat nicer way.
Myrddin is a language somewhat similar to Rust. It's still in development, so this might be worth a try if you want to check out a language that's still actively worked on and changed a lot.
Io is a really nice scripting language that's not widely known, but I think Pixar uses it for some animation related work.