3 comments
This is great. Alexis King actually stated that, had she known how popular “Parse, Don’t Validate” had been, she would have written it in a language more widely used than Haskell.
Good article on Rust's strengths with types. If you like this, you may be curious how you might build your own parse capabilities. I like the Rust crates Winnow and Nom, and also the Rust traits From and Into.
Nonempty type wrappers are a stark reminder that we are missing out on refinement types.
I was thinking about its implementation, too, and ended up deciding that it was probably a performance optimization.<p>`Vec<T>` stores all data on the heap, so getting anything out of it involves a pointer deref and possibly also an array bounds check. This `NonEmpty<T>` type keeps the first element of the list in a location that supports some low-level optimization that might make a significant difference in situations where accessing the first element is much more common than accessing subsequent elements.
Rust has a proposal for this, in the form of pattern types. It's on nightly, but quite far from being ready for prime time.