fp-course

Pretty cool. They note that they are inspired by Go by Example [0] and Rust by Example [1], and this book seems stylistically similar to the community-driven Learn X in Y minutes site [2] which covers quick syntax/conceptual overviews for many other languages as well. For the same target audience looking for free introductory coursework/exercises for Haskell, I'd recommend working through the Data61 Haskell course [3]. Brian McKenna has a nice Youtube series [4] covering it. [0] https://gobyexample.com/ [1] https://doc.rust-lang.org/rust-by-example/index.html [2] https://learnxinyminutes.com/ [3] https://github.com/system-f/fp-course#readme [4] https://www.youtube.com/watch?v=NzIZzvbplSM

As a small demonstration of the principle: https://github.com/system-f/fp-course#demonstrate-io-maintai... Scroll past the Haskell example for a moment and look at the Python. The program p2 is the same as p1, except a refactoring is performed: the call to readFile(file) is DRY'd into a variable, and this changes the meaning of the program. In the Haskell example, the same refactoring is performed. Because IO actions are treated as values in their own right, the refactoring does not change the meaning of the program. Executing p1 or p2 will have the same effect.