Potential rework of part 2.1 to reduce reliance on knowledge of other programming languages

[TheInnerLight]

Potential rework of part 2.1 to reduce reliance on knowledge of other programming languages

[opqdonut]

Good stuff. I'll need to think about how I want to incorporate this into the material. I'd rather not talk (at this point) about performance too much, but rather about expressivity. I guess I need to figure out an example function that can't be implemented without a helper function.

[TheInnerLight]

Yeah, it's difficult, I had the same issues, I originally started by thinking about the repeatString function example but I realised that, without context, students would probably wonder why the function wasn't expressed differently as:

repeatString 0 _   = ""
repeatString n str = str ++ repeatString (n-1) str

It's not obvious why this version, that doesn't need a helper function, isn't better than the presented version that accepts the result because it more closely follows the recursion examples in the previous chapter.

This function, despite also being non-tail recursive, is far less obviously problematic compared to the factorial one, which you can at least observe has pathological memory behaviour by running it.

[asarkar]

After reading the problem description, it’s not clear to me where is the reliance on other programming languages. The first implementation of factorial isn’t efficient, sure, but nothing in it requires knowledge of other programming languages.

More practically, it is highly unlikely that Haskell is someone’s first encounter with a programming language. It is not taught as a primary language in computer science beginner courses, neither it is popular enough for someone to start learning on their own.