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60 lines
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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: Standard Generic Function SLOT-UNBOUND</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_slt_mi.htm"><IMG WIDTH=40 HEIGHT=40 ALT="[Previous]" SRC="../Graphics/Prev.gif" ALIGN=Bottom></A><A REL=UP HREF="c_object.htm"><IMG WIDTH=40 HEIGHT=40 ALT="[Up]" SRC="../Graphics/Up.gif" ALIGN=Bottom></A><A REL=NEXT HREF="f_slt_va.htm"><IMG WIDTH=40 HEIGHT=40 ALT="[Next]" SRC="../Graphics/Next.gif" ALIGN=Bottom></A></H1>
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<A NAME="slot-unbound"><I>Standard Generic Function</I> <B>SLOT-UNBOUND</B></A> <P>
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<P><B>Syntax:</B><P>
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<P>
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<B>slot-unbound</B> <I>class instance slot-name</I> => <I><I>result</I><B>*</B></I><P>
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<P>
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<P><B>Method Signatures:</B><P>
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<P>
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<B>slot-unbound</B> <I>(<I>class</I><B> <A REL=DEFINITION HREF="t_t.htm#t">t</A></B>) instance slot-name</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>class</I>---the <A REL=DEFINITION HREF="26_glo_c.htm#class"><I>class</I></A> of the <I>instance</I>. <P>
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<I>instance</I>---the <I>instance</I> in which an attempt was made to <A REL=DEFINITION HREF="26_glo_r.htm#read"><I>read</I></A> the <A REL=DEFINITION HREF="26_glo_u.htm#unbound"><I>unbound</I></A> <A REL=DEFINITION HREF="26_glo_s.htm#slot"><I>slot</I></A>. <P>
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<I>slot-name</I>---the <A REL=DEFINITION HREF="26_glo_n.htm#name"><I>name</I></A> of the <A REL=DEFINITION HREF="26_glo_u.htm#unbound"><I>unbound</I></A> <A REL=DEFINITION HREF="26_glo_s.htm#slot"><I>slot</I></A>. <P>
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<I>result</I>---an <A REL=DEFINITION HREF="26_glo_o.htm#object"><I>object</I></A>. <P>
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<P><B>Description:</B><P>
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<P>
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The generic function <A REL=DEFINITION HREF="#slot-unbound"><B>slot-unbound</B></A> is called when an unbound <A REL=DEFINITION HREF="26_glo_s.htm#slot"><I>slot</I></A> is read in an <I>instance</I> whose metaclass is <A REL=DEFINITION HREF="t_std_cl.htm#standard-class"><B>standard-class</B></A>. The default <A REL=DEFINITION HREF="26_glo_m.htm#method"><I>method</I></A> signals an error of <A REL=DEFINITION HREF="26_glo_t.htm#type"><I>type</I></A> <A REL=DEFINITION HREF="e_unboun.htm#unbound-slot"><B>unbound-slot</B></A>. The name slot of the <A REL=DEFINITION HREF="e_unboun.htm#unbound-slot"><B>unbound-slot</B></A> <A REL=DEFINITION HREF="26_glo_c.htm#condition"><I>condition</I></A> is initialized to the name of the offending variable, and the instance slot of the <A REL=DEFINITION HREF="e_unboun.htm#unbound-slot"><B>unbound-slot</B></A> <A REL=DEFINITION HREF="26_glo_c.htm#condition"><I>condition</I></A> is initialized to the offending instance. <P>
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The generic function <A REL=DEFINITION HREF="#slot-unbound"><B>slot-unbound</B></A> is not intended to be called by programmers. Programmers may write <A REL=DEFINITION HREF="26_glo_m.htm#method"><I>methods</I></A> for it. The <A REL=DEFINITION HREF="26_glo_f.htm#function"><I>function</I></A> <A REL=DEFINITION HREF="#slot-unbound"><B>slot-unbound</B></A> is called only indirectly by <A REL=DEFINITION HREF="f_slt_va.htm#slot-value"><B>slot-value</B></A>. <P>
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If <A REL=DEFINITION HREF="#slot-unbound"><B>slot-unbound</B></A> returns, only the <A REL=DEFINITION HREF="26_glo_p.htm#primary_value"><I>primary value</I></A> will be used by the caller, and all other values will be ignored. <P>
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<P><B>Examples:</B> None.
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<P>
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<P><B>Affected By:</B> None.
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<P>
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<P><B>Exceptional Situations:</B><P>
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The default <A REL=DEFINITION HREF="26_glo_m.htm#method"><I>method</I></A> on <A REL=DEFINITION HREF="#slot-unbound"><B>slot-unbound</B></A> signals an error of <A REL=DEFINITION HREF="26_glo_t.htm#type"><I>type</I></A> <A REL=DEFINITION HREF="e_unboun.htm#unbound-slot"><B>unbound-slot</B></A>. <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_slt_ma.htm#slot-makunbound"><B>slot-makunbound</B></A> <P>
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<P><B>Notes:</B><P>
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<P>
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An unbound <A REL=DEFINITION HREF="26_glo_s.htm#slot"><I>slot</I></A> may occur if no <TT>:initform</TT> form was specified for the <A REL=DEFINITION HREF="26_glo_s.htm#slot"><I>slot</I></A> and the <A REL=DEFINITION HREF="26_glo_s.htm#slot"><I>slot</I></A> value has not been set, or if <A REL=DEFINITION HREF="f_slt_ma.htm#slot-makunbound"><B>slot-makunbound</B></A> has been called on the <A REL=DEFINITION HREF="26_glo_s.htm#slot"><I>slot</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/iss319.htm">SLOT-MISSING-VALUES:SPECIFY</A><LI> <A REL=CHILD HREF="../Issues/iss354.htm">UNDEFINED-VARIABLES-AND-FUNCTIONS:COMPROMISE</A><P></UL><HR>
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