33 lines
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33 lines
6.1 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: Section 3.2.4.1</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="03_bd.htm"><IMG WIDTH=40 HEIGHT=40 ALT="[Previous]" SRC="../Graphics/Prev.gif" ALIGN=Bottom></A><A REL=UP HREF="03_bd.htm"><IMG WIDTH=40 HEIGHT=40 ALT="[Up]" SRC="../Graphics/Up.gif" ALIGN=Bottom></A><A REL=NEXT HREF="03_bdb.htm"><IMG WIDTH=40 HEIGHT=40 ALT="[Next]" SRC="../Graphics/Next.gif" ALIGN=Bottom></A></H1>
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<H2>
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3.2.4.1 Externalizable Objects</H2> <P>
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The fact that the <A REL=DEFINITION HREF="26_glo_f.htm#file_compiler"><I>file compiler</I></A> represents <A REL=DEFINITION HREF="26_glo_l.htm#literal"><I>literal</I></A> <A REL=DEFINITION HREF="26_glo_o.htm#object"><I>objects</I></A> externally in a <A REL=DEFINITION HREF="26_glo_c.htm#compiled_file"><I>compiled file</I></A> and must later reconstruct suitable equivalents of those <A REL=DEFINITION HREF="26_glo_o.htm#object"><I>objects</I></A> when that <A REL=DEFINITION HREF="26_glo_f.htm#file"><I>file</I></A> is loaded imposes a need for constraints on the nature of the <A REL=DEFINITION HREF="26_glo_o.htm#object"><I>objects</I></A> that can be used as <A REL=DEFINITION HREF="26_glo_l.htm#literal"><I>literal</I></A> <A REL=DEFINITION HREF="26_glo_o.htm#object"><I>objects</I></A> in <A REL=DEFINITION HREF="26_glo_c.htm#code"><I>code</I></A> to be processed by the <A REL=DEFINITION HREF="26_glo_f.htm#file_compiler"><I>file compiler</I></A>. <P>
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An <A REL=DEFINITION HREF="26_glo_o.htm#object"><I>object</I></A> that can be used as a <A REL=DEFINITION HREF="26_glo_l.htm#literal"><I>literal</I></A> <A REL=DEFINITION HREF="26_glo_o.htm#object"><I>object</I></A> in <A REL=DEFINITION HREF="26_glo_c.htm#code"><I>code</I></A> to be processed by the <A REL=DEFINITION HREF="26_glo_f.htm#file_compiler"><I>file compiler</I></A> is called an <A REL=DEFINITION HREF="26_glo_e.htm#externalizable_object"><I>externalizable object</I></A>. <P>
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We define that two <A REL=DEFINITION HREF="26_glo_o.htm#object"><I>objects</I></A> are <A REL=DEFINITION HREF="26_glo_s.htm#similar"><I>similar</I></A> if they satisfy a two-place conceptual equivalence predicate (defined below), which is independent of the <A REL=DEFINITION HREF="26_glo_l.htm#lisp_image"><I>Lisp image</I></A> so that the two <A REL=DEFINITION HREF="26_glo_o.htm#object"><I>objects</I></A> in different <A REL=DEFINITION HREF="26_glo_l.htm#lisp_image"><I>Lisp images</I></A> can be understood to be equivalent under this predicate. Further, by inspecting the definition of this conceptual predicate, the programmer can anticipate what aspects of an <A REL=DEFINITION HREF="26_glo_o.htm#object"><I>object</I></A> are reliably preserved by <A REL=DEFINITION HREF="26_glo_f.htm#file"><I>file</I></A> <A REL=DEFINITION HREF="26_glo_c.htm#compilation"><I>compilation</I></A>. <P>
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The <A REL=DEFINITION HREF="26_glo_f.htm#file_compiler"><I>file compiler</I></A> must cooperate with the <A REL=DEFINITION HREF="26_glo_l.htm#loader"><I>loader</I></A> in order to assure that in each case where an <A REL=DEFINITION HREF="26_glo_e.htm#externalizable_object"><I>externalizable object</I></A> is processed as a <A REL=DEFINITION HREF="26_glo_l.htm#literal"><I>literal</I></A> <A REL=DEFINITION HREF="26_glo_o.htm#object"><I>object</I></A>, the <A REL=DEFINITION HREF="26_glo_l.htm#loader"><I>loader</I></A> will construct a <A REL=DEFINITION HREF="26_glo_s.htm#similar"><I>similar</I></A> <A REL=DEFINITION HREF="26_glo_o.htm#object"><I>object</I></A>. <P>
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The set of <A REL=DEFINITION HREF="26_glo_o.htm#object"><I>objects</I></A> that are <A REL=DEFINITION HREF="26_glo_e.htm#externalizable_object"><I>externalizable objects</I></A> are those for which the new conceptual term ``<A REL=DEFINITION HREF="26_glo_s.htm#similar"><I>similar</I></A>'' is defined, such that when a <A REL=DEFINITION HREF="26_glo_c.htm#compiled_file"><I>compiled file</I></A> is <I>loaded</I>, an <A REL=DEFINITION HREF="26_glo_o.htm#object"><I>object</I></A> can be constructed which can be shown to be <A REL=DEFINITION HREF="26_glo_s.htm#similar"><I>similar</I></A> to the original <A REL=DEFINITION HREF="26_glo_o.htm#object"><I>object</I></A> which existed at the time the <A REL=DEFINITION HREF="26_glo_f.htm#file_compiler"><I>file compiler</I></A> was operating. <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/iss081.htm">CONSTANT-COMPILABLE-TYPES:SPECIFY</A><P></UL><HR>
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