I think you're looking for "combinatorial species". This paper gives a decent introduction in a programming context: https://www.cas.mcmaster.ca/~carette/public

I think you're looking for "combinatorial species". This paper gives a decent introduction in a programming context: https://www.cas.mcmaster.ca/~carette/publications/labelled-structures-draft.pdf https://www.cas.mcmaster.ca/~carette/publications/labelled-s...