我如何要求 Lisp 编译器忽略（标签种类）函数？

我盯着斯蒂尔的Common Lisp 语言直到我脸色发青，仍然有这个问题。如果我编译：

(defun x ()
  (labels ((y ()))
    5))
(princ (x))
(terpri)

有时候是这样的：

home:~/clisp/experiments$ clisp -c -q x.lisp
;; Compiling file /u/home/clisp/experiments/x.lisp ...
WARNING in lines 1..3 :
function X-Y is not used.
Misspelled or missing IGNORE declaration?
;; Wrote file /u/home/clisp/experiments/x.fas
0 errors, 1 warning
home:~/clisp/experiments$ 

很公平。那么如何让编译器忽略函数 y 呢？我试过这个：

(defun x ()
  (labels (#+ignore(y ()))
    5))
(princ (x))
(terpri)

它起作用了：

home:~/clisp/experiments$ clisp -c -q y.lisp
;; Compiling file /u/home/clisp/experiments/y.lisp ...
;; Wrote file /u/home/clisp/experiments/y.fas
0 errors, 0 warnings
home:~/clisp/experiments$ 

但不知何故，我不认为警告暗示我应该这样做。

我该怎么办？

GNU CLISP 要求您declare http://www.lispworks.com/documentation/HyperSpec/Body/s_declar.htm函数为ignored http://www.lispworks.com/documentation/HyperSpec/Body/d_ignore.htm#ignore.

(defun x ()
  (labels ((y ()))
    (declare (ignore (function y)))
    5))

或者（特别是如果这是宏扩展的结果，则取决于用户是否y实际使用与否），

(defun x ()
  (labels ((y ()))
    (declare (ignorable (function y)))
    5))

（无论您希望在哪里写(function y)，您可以自由使用读者缩写#'y反而。）