He did provide them but didn't do a very good job, tbh. Types capture the behavior you want to express in your program and Rich ultimately concluded that types

He did provide them but didn't do a very good job, tbh. Types capture the behavior you want to express in your program and Rich ultimately concluded that types could no achieve this for transducers. On the other hand, many libraries since then have generally shown that types can and do... It's just that Rich's types didn't.