例如，我有这个包定义，它遮蔽了 COMMON-LISP:LISTEN ：

(defpackage :shadows
  (:use :common-lisp)
  (:shadow #:listen)
  (:export #:listen))

然后我想使用另一个包中的这个包，比如说

(defpackage :light
  (:use :common-lisp
        :shadows))

如果我在使用包时无法真正覆盖 Common Lisp 符号，那么影子的目的是什么？

Simple

The :shadow论证defpackage http://clhs.lisp.se/Body/m_defpkg.htm影响包的定义shadows, 不是后来使用的shadows in light.

你需要使用shadowing-import http://clhs.lisp.se/Body/f_shdw_i.htm:

(defpackage #:shadows
  (:use #:common-lisp)
  (:shadow #:listen)
  (:export #:listen))
(defpackage #:light
  (:shadowing-import-from #:shadows #:listen)
  (:use #:common-lisp #:shadows))
(eq 'light::listen 'shadows:listen)
==> T
(describe 'light::listen)
==>
SHADOWS:LISTEN is the symbol SHADOWS:LISTEN, lies in #<PACKAGE SHADOWS>,
is accessible in 2 packages LIGHT, SHADOWS.

 #<PACKAGE SHADOWS> is the package named SHADOWS.
 It imports the external symbols of 1 package COMMON-LISP and
 exports 1 symbol to 1 package LIGHT.

Bulk

如果您需要进行批量阴影，则需要使用单独的函数 （make-package http://clhs.lisp.se/Body/f_mk_pkg.htm, import http://clhs.lisp.se/Body/f_import.htm, export http://clhs.lisp.se/Body/f_export.htm, shadow http://clhs.lisp.se/Body/f_shadow.htm, use-package http://clhs.lisp.se/Body/f_use_pk.htm):

(defparameter *my-shadow-list* '(#:car #:cdr))
(make-package '#:my-package :use nil)
(import *my-shadow-list* '#:my-package)
(export *my-shadow-list* '#:my-package)
(shadow *my-shadow-list* '#:my-package)
(use-package '#:cl '#:my-package)
(make-package '#:my-user)
(shadowing-import *my-shadow-list* '#:my-user)
(use-package '(#:cl #:my-package) '#:my-user)
(describe 'my-user::car)
==>
MY-PACKAGE:CAR is the symbol MY-PACKAGE:CAR, lies in #<PACKAGE MY-PACKAGE>,
is accessible in 2 packages MY-PACKAGE, MY-USER.

 #<PACKAGE MY-PACKAGE> is the package named MY-PACKAGE.
 It imports the external symbols of 1 package COMMON-LISP and
 exports 2 symbols to 1 package MY-USER.

你可能会发现macroexpand-1 http://clhs.lisp.se/Body/f_mexp_.htm对于决定如何到达您需要去的地方很有用：

(macroexpand-1 '(defpackage #:light
                 (:shadowing-import-from #:shadows #:listen)
                 (:use #:common-lisp #:shadows)))
==>
(EVAL-WHEN (:COMPILE-TOPLEVEL :LOAD-TOPLEVEL :EXECUTE)
 (SYSTEM::%IN-PACKAGE "LIGHT" :NICKNAMES 'NIL :USE 'NIL :CASE-SENSITIVE NIL
  :CASE-INVERTED NIL)
 (SYSTEM::SHADOWING-IMPORT-CERROR "LISTEN" "SHADOWS" NIL "LIGHT")
 (USE-PACKAGE '("COMMON-LISP" "SHADOWS") "LIGHT") (FIND-PACKAGE "LIGHT")) ;
T

附言。对于代码可读性而言，隐藏 ANSI CL 标准名称并不是一个好主意。