Transducers were at least 20 years old when Clojure was first created. I have the book "Common Lisp: the language" from 1989 that describes transducers as found

Transducers were at least 20 years old when Clojure was first created. I have the book "Common Lisp: the language" from 1989 that describes transducers as found in Clojure. Clojure is the only language where it is baked in that prominently though.