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35 lines
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<TITLE>CLHS: Section 19.2.2.2.3</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="19_bbbb.htm"><IMG WIDTH=40 HEIGHT=40 ALT="[Previous]" SRC="../Graphics/Prev.gif" ALIGN=Bottom></A><A REL=UP HREF="19_bbb.htm"><IMG WIDTH=40 HEIGHT=40 ALT="[Up]" SRC="../Graphics/Up.gif" ALIGN=Bottom></A><A REL=NEXT HREF="19_bbbca.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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19.2.2.2.3 :UNSPECIFIC as a Component Value</H2> <P>
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If <TT>:unspecific</TT> is the value of a <A REL=DEFINITION HREF="26_glo_p.htm#pathname"><I>pathname</I></A> component, the component is considered to be ``absent'' or to ``have no meaning'' in the <A REL=DEFINITION HREF="26_glo_f.htm#filename"><I>filename</I></A> being represented by the <A REL=DEFINITION HREF="26_glo_p.htm#pathname"><I>pathname</I></A>. <P>
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Whether a value of <TT>:unspecific</TT> is permitted for any component on any given <A REL=DEFINITION HREF="26_glo_f.htm#file_system"><I>file system</I></A> accessible to the <A REL=DEFINITION HREF="26_glo_i.htm#implementation"><I>implementation</I></A> is <A REL=DEFINITION HREF="26_glo_i.htm#implementation-defined"><I>implementation-defined</I></A>. A <A REL=DEFINITION HREF="26_glo_c.htm#conforming_program"><I>conforming program</I></A> must never unconditionally use a <TT>:unspecific</TT> as the value of a <A REL=DEFINITION HREF="26_glo_p.htm#pathname"><I>pathname</I></A> component because such a value is not guaranteed to be permissible in all implementations. However, a <A REL=DEFINITION HREF="26_glo_c.htm#conforming_program"><I>conforming program</I></A> can, if it is careful, successfully manipulate user-supplied data which contains or refers to non-portable <A REL=DEFINITION HREF="26_glo_p.htm#pathname"><I>pathname</I></A> components. And certainly a <A REL=DEFINITION HREF="26_glo_c.htm#conforming_program"><I>conforming program</I></A> should be prepared for the possibility that any components of a <A REL=DEFINITION HREF="26_glo_p.htm#pathname"><I>pathname</I></A> could be <TT>:unspecific</TT>. <P>
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When <I>reading</I>[1] the value of any <A REL=DEFINITION HREF="26_glo_p.htm#pathname"><I>pathname</I></A> component, <A REL=DEFINITION HREF="26_glo_c.htm#conforming_program"><I>conforming programs</I></A> should be prepared for the value to be <TT>:unspecific</TT>. <P>
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When <I>writing</I>[1] the value of any <A REL=DEFINITION HREF="26_glo_p.htm#pathname"><I>pathname</I></A> component, the consequences are undefined if <TT>:unspecific</TT> is given for a <A REL=DEFINITION HREF="26_glo_p.htm#pathname"><I>pathname</I></A> in a <A REL=DEFINITION HREF="26_glo_f.htm#file_system"><I>file system</I></A> for which it does not make sense. <P>
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<A REL=CHILD HREF="19_bbbca.htm"><H2>
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19.2.2.2.3.1 Relation between component values NIL and :UNSPECIFIC</H2></A><P><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/iss266.htm">PATHNAME-UNSPECIFIC-COMPONENT:NEW-TOKEN</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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