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| ANSI Common Lisp 11 Packages 11.2 Dictionary of Packages
11.2.9 shadow | Function
  Syntax: shadow symbol-names `&optional` package t Arguments and Values: symbol-names - a designator for a list of string designators. package - a package designator. The default is the current package. Description: shadow assures that symbols with names given by symbol-names are present in the package. Specifically, package is searched for symbols with the names supplied by symbol-names. For each such name, if a corresponding symbol is not present in package (directly, not by inheritance), then a corresponding symbol is created with that name, and inserted into package as an internal symbol. The corresponding symbol, whether pre-existing or newly created, is then added, if not already present, to the shadowing symbols list of package. Examples:
       (package-shadowing-symbols (make-package 'temp))   NIL
       (find-symbol 'car 'temp)   CAR, :INHERITED
       (shadow 'car 'temp)   T
       (find-symbol 'car 'temp)   TEMP::CAR, :INTERNAL
       (package-shadowing-symbols 'temp)  (TEMP::CAR)
       (make-package 'test-1)  #<PACKAGE "TEST-1">
       (intern "TEST" (find-package 'test-1))   TEST-1::TEST, NIL
       (shadow 'test-1::test (find-package 'test-1))   T
       (shadow 'TEST (find-package 'test-1))   T
       (assert (not (null (member 'test-1::test (package-shadowing-symbols
                                                  (find-package 'test-1))))))

       (make-package 'test-2)  #<PACKAGE "TEST-2">
       (intern "TEST" (find-package 'test-2))   TEST-2::TEST, NIL
       (export 'test-2::test (find-package 'test-2))   T
       (use-package 'test-2 (find-package 'test-1))    ;should not error
Side Effects: shadow changes the state of the package system in such a way that the package consistency rules do not hold across the change. Affected By: Current state of the package system. See Also: package-shadowing-symbols, Section 11.1 Package Concepts Notes: If a symbol with a name in symbol-names already exists in package, but by inheritance, the inherited symbol becomes shadowed3 by a newly created internal symbol. Allegro CL Implementation Details: None.

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