80 lines
6.3 KiB
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80 lines
6.3 KiB
HTML
<!-- Common Lisp HyperSpec (TM), version 7.0 generated by Kent M. Pitman on Mon, 11-Apr-2005 2:31am EDT -->
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<TITLE>CLHS: Function SHADOW</TITLE>
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<H1><A REV=MADE HREF="http://www.lispworks.com/"><IMG WIDTH=80 HEIGHT=65 ALT="[LISPWORKS]" SRC="../Graphics/LWSmall.gif" ALIGN=Bottom></A><A REL=TOP HREF="../Front/index.htm"><IMG WIDTH=237 HEIGHT=65 ALT="[Common Lisp HyperSpec (TM)]" SRC="../Graphics/CLHS_Sm.gif" ALIGN=Bottom></A> <A REL=PREV HREF="f_rn_pkg.htm"><IMG WIDTH=40 HEIGHT=40 ALT="[Previous]" SRC="../Graphics/Prev.gif" ALIGN=Bottom></A><A REL=UP HREF="c_packag.htm"><IMG WIDTH=40 HEIGHT=40 ALT="[Up]" SRC="../Graphics/Up.gif" ALIGN=Bottom></A><A REL=NEXT HREF="f_shdw_i.htm"><IMG WIDTH=40 HEIGHT=40 ALT="[Next]" SRC="../Graphics/Next.gif" ALIGN=Bottom></A></H1>
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<HR>
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<A NAME="shadow"><I>Function</I> <B>SHADOW</B></A> <P>
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<P><B>Syntax:</B><P>
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<P>
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<B>shadow</B> <I>symbol-names <TT>&optional</TT> package</I> => <I><A REL=DEFINITION HREF="a_t.htm#t"><B>t</B></A></I><P>
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<P>
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<P><B>Arguments and Values:</B><P>
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<P>
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<I>symbol-names</I>---a <A REL=DEFINITION HREF="26_glo_d.htm#designator"><I>designator</I></A> for a <A REL=DEFINITION HREF="26_glo_l.htm#list"><I>list</I></A> of <A REL=DEFINITION HREF="26_glo_s.htm#string_designator"><I>string designators</I></A>. <P>
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<I>package</I>---a <A REL=DEFINITION HREF="26_glo_p.htm#package_designator"><I>package designator</I></A>. The default is the <A REL=DEFINITION HREF="26_glo_c.htm#current_package"><I>current package</I></A>. <P>
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<P><B>Description:</B><P>
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<P>
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<A REL=DEFINITION HREF="#shadow"><B>shadow</B></A> assures that <A REL=DEFINITION HREF="26_glo_s.htm#symbol"><I>symbols</I></A> with names given by <I>symbol-names</I> are <A REL=DEFINITION HREF="26_glo_p.htm#present"><I>present</I></A> in the <I>package</I>. <P>
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Specifically, <I>package</I> is searched for <A REL=DEFINITION HREF="26_glo_s.htm#symbol"><I>symbols</I></A> with the <A REL=DEFINITION HREF="26_glo_n.htm#name"><I>names</I></A> supplied by <I>symbol-names</I>. For each such <A REL=DEFINITION HREF="26_glo_n.htm#name"><I>name</I></A>, if a corresponding <A REL=DEFINITION HREF="26_glo_s.htm#symbol"><I>symbol</I></A> is not <A REL=DEFINITION HREF="26_glo_p.htm#present"><I>present</I></A> in <I>package</I> (directly, not by inheritance), then a corresponding <A REL=DEFINITION HREF="26_glo_s.htm#symbol"><I>symbol</I></A> is created with that <A REL=DEFINITION HREF="26_glo_n.htm#name"><I>name</I></A>, and inserted into <I>package</I> as an <A REL=DEFINITION HREF="26_glo_i.htm#internal_symbol"><I>internal symbol</I></A>. The corresponding <A REL=DEFINITION HREF="26_glo_s.htm#symbol"><I>symbol</I></A>, whether pre-existing or newly created, is then added, if not already present, to the <A REL=DEFINITION HREF="26_glo_s.htm#shadowing_symbols_list"><I>shadowing symbols list</I></A> of <I>package</I>. <P>
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<P><B>Examples:</B><P>
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<P>
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<PRE>
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(package-shadowing-symbols (make-package 'temp)) => NIL
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(find-symbol 'car 'temp) => CAR, :INHERITED
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(shadow 'car 'temp) => T
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(find-symbol 'car 'temp) => TEMP::CAR, :INTERNAL
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(package-shadowing-symbols 'temp) => (TEMP::CAR)
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</PRE>
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</TT> <P>
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<PRE>
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(make-package 'test-1) => #<PACKAGE "TEST-1">
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(intern "TEST" (find-package 'test-1)) => TEST-1::TEST, NIL
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(shadow 'test-1::test (find-package 'test-1)) => T
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(shadow 'TEST (find-package 'test-1)) => T
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(assert (not (null (member 'test-1::test (package-shadowing-symbols
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(find-package 'test-1))))))
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(make-package 'test-2) => #<PACKAGE "TEST-2">
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(intern "TEST" (find-package 'test-2)) => TEST-2::TEST, NIL
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(export 'test-2::test (find-package 'test-2)) => T
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(use-package 'test-2 (find-package 'test-1)) ;should not error
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</PRE>
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</TT> <P>
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<P><B>Side Effects:</B><P>
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<P>
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<A REL=DEFINITION HREF="#shadow"><B>shadow</B></A> changes the state of the package system in such a way that the package consistency rules do not hold across the change. <P>
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<P><B>Affected By:</B><P>
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<P>
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Current state of the package system. <P>
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<P><B>Exceptional Situations:</B> None.
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<P>
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<P><B>See Also:</B><P>
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<P>
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<A REL=DEFINITION HREF="f_pkg_sh.htm#package-shadowing-symbols"><B>package-shadowing-symbols</B></A>, <A REL=CHILD HREF="11_a.htm">Section 11.1 (Package Concepts)</A> <P>
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<P><B>Notes:</B><P>
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<P>
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If a <A REL=DEFINITION HREF="26_glo_s.htm#symbol"><I>symbol</I></A> with a name in <I>symbol-names</I> already exists in <I>package</I>, but by inheritance, the inherited symbol becomes <I>shadowed</I>[3] by a newly created <A REL=DEFINITION HREF="26_glo_i.htm#internal_symbol"><I>internal symbol</I></A>. <P>
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<P><HR>The following <A REL=META HREF="../Front/X3J13Iss.htm">X3J13 cleanup issues</A>, <I>not part of the specification</I>, apply to this section:<P><UL><LI> <A REL=CHILD HREF="../Issues/iss313.htm">SHADOW-ALREADY-PRESENT</A><LI> <A REL=CHILD HREF="../Issues/iss254.htm">PACKAGE-FUNCTION-CONSISTENCY:MORE-PERMISSIVE</A><LI> <A REL=CHILD HREF="../Issues/iss314.htm">SHADOW-ALREADY-PRESENT:WORKS</A><P></UL><HR>
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<A REL=COPYRIGHT HREF="../Front/Help.htm#Legal"><I>Copyright 1996-2005, LispWorks Ltd. All rights reserved.</I></A><P>
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