My actual "production" implementation of this concept does support that: https://github.com/tavianator/bfs/blob/main/configure https://github.com/tavianator/bfs

My actual "production" implementation of this concept does support that: https://github.com/tavianator/bfs/blob/main/configure https://github.com/tavianator/bfs/blob/main/configure But I wanted the blog post sized version to be simpler for exposition.