Haskell の $ もどき in Common Lisp

dollar_sign.lisp

;; Haskell の $ もどき in Common Lisp
;; http://practical-scheme.net/wiliki/wiliki.cgi?Gauche%3A%24

;; (fn1 $ fn2 $ fn3 $ fn4 x) -> (fn1 (fn2 (fn3 (fn4 x))))
(defun $-expand (forms)
  (cond ((null forms)
	 nil)
	((eq '$ (car forms))
	 (list ($-expand (cdr forms))))
	(t
	 (cons (car forms) ($-expand (cdr forms))))))

(defmacro $ (&body forms)
  ($-expand forms))

#|
CL-USER> (macroexpand-1 '($ fn1 $ fn2 $ fn3 $ fn4 x))

(FN1 (FN2 (FN3 (FN4 X))))
T
CL-USER> (macroexpand-1 '($ f a b c))

(F A B C)
T
CL-USER> (macroexpand-1 '($ f $ g a b c))

(F (G A B C))
T
CL-USER> (macroexpand-1 '($ f $ g $ h a b c))

(F (G (H A B C)))
T
CL-USER> (macroexpand-1 '($ f a $ g b $ h c))

(F A (G B (H C)))
T
CL-USER> ($ 1+ $ 1+ 2)
4
CL-USER> ($ 1+ $ 1+ ($ 1+ 2))
5
|#