Previously, we introduced a method for writing performant stack safe recursion in Rust for a single recursive data structure. This post uses the same ideas to implement a single recursion backend that can collapse or expand any recursive data structure.
This is a post about writing elegant and performant recursive algorithms in Rust. It makes heavy use of a pattern from Haskell called recursion schemes, but you don't need to know anything about that; it's just an implementation detail. Instead, as motivation, I have benchmarks showing a 14-34% improvement over the typical boxed pointer representation of recursive data structures in Rust.