自制@裝飾器

Decorators.lisp

(defun Decorators (stream ch1)
  (declare (ignore ch1))
  (let ((Decorator (read stream))
        (the-func-form (read stream)))
    (unless (eq (first the-func-form) 'defun)
      (error "need 'defun"))

    (let ((the-func-name (second the-func-form))
          (the-func-args (third the-func-form))
          (the-func (cdddr the-func-form)))
      `(flet ((old-func ,the-func-args ,@the-func))
         (defun ,the-func-name ,the-func-args
           (funcall (,Decorator #'old-func) ,@the-func-args))))))


(defun print-hello (func)
  (print 'hello)
  func)

(defun hello-name (name)
  (format t "~&Hello, ~A~%" name))

(hello-name "john")

(funcall (print-hello #'hello-name) "john")


(set-macro-character #\@
                     #'Decorators)
@print-hello
(defun hello-world ()
  (format t "~&Hello, world~%"))
#| output the result
(print (with-input-from-string (s "print-hello
                           (defun hello-world ()
                             (format t \"~&Hello, world~%\"))")
         (Decorators s #\@)))
|#
(hello-world)

@print-hello
(defun show-num (num)
  (print num))

(show-num 10)

#|
(print (with-input-from-string (s "print-hello
                           (defun show-num (num)
                             (print num))")
         (Decorators s #\@)))
|#