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8.7 KiB
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67 lines
8.7 KiB
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<!-- 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 EXPORT</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="t_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_find_s.htm"><IMG WIDTH=40 HEIGHT=40 ALT="[Next]" SRC="../Graphics/Next.gif" ALIGN=Bottom></A></H1>
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<A NAME="export"><I>Function</I> <B>EXPORT</B></A> <P>
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<P><B>Syntax:</B><P>
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<P>
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<B>export</B> <I>symbols <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>symbols</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#symbol"><I>symbols</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="#export"><B>export</B></A> makes one or more <I>symbols</I> that are <A REL=DEFINITION HREF="26_glo_a.htm#accessible"><I>accessible</I></A> in <I>package</I> (whether directly or by inheritance) be <A REL=DEFINITION HREF="26_glo_e.htm#external_symbol"><I>external symbols</I></A> of that <I>package</I>. <P>
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If any of the <I>symbols</I> is already <A REL=DEFINITION HREF="26_glo_a.htm#accessible"><I>accessible</I></A> as an <A REL=DEFINITION HREF="26_glo_e.htm#external_symbol"><I>external symbol</I></A> of <I>package</I>, <A REL=DEFINITION HREF="#export"><B>export</B></A> has no effect on that <A REL=DEFINITION HREF="26_glo_s.htm#symbol"><I>symbol</I></A>. If the <I>symbol</I> is <A REL=DEFINITION HREF="26_glo_p.htm#present"><I>present</I></A> in <I>package</I> as an internal symbol, it is simply changed to external status. If it is <A REL=DEFINITION HREF="26_glo_a.htm#accessible"><I>accessible</I></A> as an <A REL=DEFINITION HREF="26_glo_i.htm#internal_symbol"><I>internal symbol</I></A> via <A REL=DEFINITION HREF="f_use_pk.htm#use-package"><B>use-package</B></A>, it is first <I>imported</I> into <I>package</I>, then <A REL=DEFINITION HREF="26_glo_e.htm#exported"><I>exported</I></A>. (The <I>symbol</I> is then <A REL=DEFINITION HREF="26_glo_p.htm#present"><I>present</I></A> in the <I>package</I> whether or not <I>package</I> continues to use the <A REL=DEFINITION HREF="26_glo_p.htm#package"><I>package</I></A> through which the <A REL=DEFINITION HREF="26_glo_s.htm#symbol"><I>symbol</I></A> was originally inherited.) <P>
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<A REL=DEFINITION HREF="#export"><B>export</B></A> makes each <I>symbol</I> <A REL=DEFINITION HREF="26_glo_a.htm#accessible"><I>accessible</I></A> to all the <A REL=DEFINITION HREF="26_glo_p.htm#package"><I>packages</I></A> that use <I>package</I>. All of these <A REL=DEFINITION HREF="26_glo_p.htm#package"><I>packages</I></A> are checked for name conflicts: <TT>(export </TT><I>s</I><TT> </TT><I>p</I><TT>)</TT> does <TT>(find-symbol (symbol-name </TT><I>s</I><TT>) </TT><I>q</I><TT>)</TT> for each package <I>q</I> in <TT>(package-used-by-list </TT><I>p</I><TT>)</TT>. Note that in the usual case of an <A REL=DEFINITION HREF="#export"><B>export</B></A> during the initial definition of a <A REL=DEFINITION HREF="26_glo_p.htm#package"><I>package</I></A>, the result of <A REL=DEFINITION HREF="f_pkg__1.htm#package-used-by-list"><B>package-used-by-list</B></A> is <A REL=DEFINITION HREF="a_nil.htm#nil"><B>nil</B></A> and the name-conflict checking takes negligible time. When multiple changes are to be made, for example when <A REL=DEFINITION HREF="#export"><B>export</B></A> is given a <I>list</I> of <I>symbols</I>, it is permissible for the implementation to process each change separately, so that aborting from a name conflict caused by any but the first <I>symbol</I> in the <A REL=DEFINITION HREF="26_glo_l.htm#list"><I>list</I></A> does not unexport the first <I>symbol</I> in the <I>list</I>. However, aborting from a name-conflict error caused by <A REL=DEFINITION HREF="#export"><B>export</B></A> of one of <I>symbols</I> does not leave that <A REL=DEFINITION HREF="26_glo_s.htm#symbol"><I>symbol</I></A> <A REL=DEFINITION HREF="26_glo_a.htm#accessible"><I>accessible</I></A> to some <A REL=DEFINITION HREF="26_glo_p.htm#package"><I>packages</I></A> and <A REL=DEFINITION HREF="26_glo_i.htm#inaccessible"><I>inaccessible</I></A> to others; with respect to each of <I>symbols</I> processed, <A REL=DEFINITION HREF="#export"><B>export</B></A> behaves as if it were as an atomic operation. <P>
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A name conflict in <A REL=DEFINITION HREF="#export"><B>export</B></A> between one of <I>symbols</I> being exported and a <A REL=DEFINITION HREF="26_glo_s.htm#symbol"><I>symbol</I></A> already <A REL=DEFINITION HREF="26_glo_p.htm#present"><I>present</I></A> in a <A REL=DEFINITION HREF="26_glo_p.htm#package"><I>package</I></A> that would inherit the newly-exported <A REL=DEFINITION HREF="26_glo_s.htm#symbol"><I>symbol</I></A> may be resolved in favor of the exported <A REL=DEFINITION HREF="26_glo_s.htm#symbol"><I>symbol</I></A> by uninterning the other one, or in favor of the already-present <A REL=DEFINITION HREF="26_glo_s.htm#symbol"><I>symbol</I></A> by making it a shadowing symbol. <P>
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<P><B>Examples:</B><P>
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<P>
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<PRE>
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(make-package 'temp :use nil) => #<PACKAGE "TEMP">
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(use-package 'temp) => T
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(intern "TEMP-SYM" 'temp) => TEMP::TEMP-SYM, NIL
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(find-symbol "TEMP-SYM") => NIL, NIL
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(export (find-symbol "TEMP-SYM" 'temp) 'temp) => T
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(find-symbol "TEMP-SYM") => TEMP-SYM, :INHERITED
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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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The package system is modified. <P>
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<P><B>Affected By:</B><P>
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<P>
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<A REL=DEFINITION HREF="26_glo_a.htm#accessible"><I>Accessible</I></A> <A REL=DEFINITION HREF="26_glo_s.htm#symbol"><I>symbols</I></A>. <P>
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<P><B>Exceptional Situations:</B><P>
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<P>
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If any of the <I>symbols</I> is not <A REL=DEFINITION HREF="26_glo_a.htm#accessible"><I>accessible</I></A> at all in <I>package</I>, an error of <A REL=DEFINITION HREF="26_glo_t.htm#type"><I>type</I></A> <A REL=DEFINITION HREF="e_pkg_er.htm#package-error"><B>package-error</B></A> is signaled that is <A REL=DEFINITION HREF="26_glo_c.htm#correctable"><I>correctable</I></A> by permitting the <A REL=DEFINITION HREF="26_glo_u.htm#user"><I>user</I></A> to interactively specify whether that <A REL=DEFINITION HREF="26_glo_s.htm#symbol"><I>symbol</I></A> should be <I>imported</I>. <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_import.htm#import"><B>import</B></A>, <A REL=DEFINITION HREF="f_unexpo.htm#unexport"><B>unexport</B></A>, <A REL=CHILD HREF="11_a.htm">Section 11.1 (Package Concepts)</A> <P>
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<P><B>Notes:</B> None.
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<P>
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<P><HR>The following <A REL=META HREF="../Front/X3J13Iss.htm">X3J13 cleanup issue</A>, <I>not part of the specification</I>, applies to this section:<P><UL><LI> <A REL=CHILD HREF="../Issues/iss254.htm">PACKAGE-FUNCTION-CONSISTENCY:MORE-PERMISSIVE</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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