Haskell
Haskell is a statically-typed, purely functional programming language known for its strong type system and lazy evaluation. It is primarily used for academic research, formal verification, and high-level system development.
Hello, world code example:
main = putStrLn "Hello world!"
Popularity: 2.1% of developers are using or have used this language.*
*According to StackOverflow's 2023 survey.
Repositories on GitHub: 138,356