I think the point of the exercise is to start with streams as they are defined in Haskell and then gradually improve them, as an experiment or demonstration. Th

I think the point of the exercise is to start with streams as they are defined in Haskell and then gradually improve them, as an experiment or demonstration. The post is aimed at Haskell programmers who might be interested in Rust. If the goal was to build efficient and flexible streams in Rust, then indeed, you wouldn't start like this.