Generators II: The Question Mark Problem

Posted on February 18, 2019 by woboats@gmail.com (boats)

This is my second post on the design of generators. In the first post, I outlined what an MVP of the feature would look like. In this post, I want to take a look at the first design issue for the feature: how it integrates with the ? operator. To explain exactly what I mean, let’s start with a specific motivating example: // This generator yields the number of alphanumeric characters in every line // in some io::Read'able data // exact sign function declaration syntax left unspecified on purpose |data| { let mut buffered_data = BufReader::new(data); let mut string = String::new(); while buffered_data.