Note:quack-pretty-lambda-p

え、2003-01-03の時点でもう入ってる？

;; Version 0.17 (2003-01-03)
;; * Pretty-lambda is supported well under GNU Emacs 21, when using PLT
;; Style fontification. Enable via the Options menu. (Based on
;; approach by Stefan Monnier; suggested by Ray Racine.)

ソース読んでないだけだったorz