shadow

ToC

Allegro CL

ANSI Common Lisp

11 Packages

11.2 Dictionary of Packages

11.2.9 shadow

Function

Syntax:

shadow symbol-names &optional package

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.