Idris
Idris is a general-purpose, purely functional programming language with dependent types. It is primarily used for research in formal methods, theorem proving, and programming language design.
Hello, world code example:
module Main
main : IO ()
main = putStrLn "Hello world!"
Popularity: Less than 1% of developers are using or have used this language.*
*According to StackOverflow's 2023 survey.
Repositories on GitHub: 2,049