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>update-instance-for-redefined-class | Common Lisp Nova Spec</TITLE
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><TD ALIGN="LEFT" VALIGN="BASELINE" WIDTH="100%" CLASS="name"
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><SPAN CLASS="idx" DATA-KIND="idxref" DATA-TERM="update-instance-for-redefined-class"
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></SPAN
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><B
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>update-instance-for-redefined-class</B
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></TD
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><TD ALIGN="RIGHT" VALIGN="BASELINE" WIDTH="0" NOWRAP="NOWRAP" CLASS="ftype"
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><I
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>Standard</I
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> <I
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>Generic</I
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> <I
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>Function</I
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></TD
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></TR
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></TABLE
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><HR
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></DIV
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><UL CLASS="subtoc"
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></UL
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><DL
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><DT
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><B
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>Syntax</B
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></DT
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><DD
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><TABLE CELLPADDING="0" CELLSPACING="0"
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><TR
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><TD VALIGN="BASELINE" ALIGN="LEFT" NOWRAP="NOWRAP"
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><B
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>update-instance-for-redefined-class</B
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><SPAN CLASS="cmssi"
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> </SPAN
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></TD
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><TD VALIGN="BASELINE" ALIGN="LEFT"
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><SPAN CLASS="cmssi"
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>instance</SPAN
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><BR
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><SPAN CLASS="cmssi"
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>added-slots</SPAN
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> <SPAN CLASS="cmssi"
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>discarded-slots</SPAN
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><BR
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><SPAN CLASS="cmssi"
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>property-list</SPAN
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><BR
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><SPAN CLASS="cmtt"
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>&rest</SPAN
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> <SPAN CLASS="cmssi"
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>initargs</SPAN
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> <SPAN CLASS="cmtt"
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>&key</SPAN
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> <SPAN CLASS="cmtt"
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>&allow-other-keys</SPAN
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></TD
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></TR
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></TABLE
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><DIV
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><SPAN CLASS="cmsy"
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><SPAN CLASS="arrow"
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>→</SPAN
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></SPAN
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> <SPAN CLASS="cmsy"
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>{</SPAN
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><VAR CLASS="param"
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>result</VAR
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><SPAN CLASS="cmsy"
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>}</SPAN
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><SPAN CLASS="cmr"
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>*</SPAN
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></DIV
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></DD
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><DT
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><B
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>Method Signatures</B
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></DT
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><DD
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><TABLE CELLPADDING="0" CELLSPACING="0"
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><TR
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><TD VALIGN="BASELINE" ALIGN="LEFT" NOWRAP="NOWRAP"
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><B
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>update-instance-for-redefined-class</B
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><SPAN CLASS="cmr"
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> </SPAN
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></TD
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><TD VALIGN="BASELINE" ALIGN="LEFT"
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><SPAN CLASS="cmr"
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>(</SPAN
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><VAR CLASS="param"
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>instance</VAR
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> <A HREF="t_standard-object.html" CLASS="typeref"
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><B
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>standard-object</B
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></A
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><SPAN CLASS="cmr"
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>)</SPAN
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><BR
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><SPAN CLASS="cmssi"
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>added-slots</SPAN
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> <SPAN CLASS="cmssi"
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>discarded-slots</SPAN
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><BR
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><SPAN CLASS="cmssi"
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>property-list</SPAN
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><BR
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><SPAN CLASS="cmtt"
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>&rest</SPAN
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> <SPAN CLASS="cmssi"
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>initargs</SPAN
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></TD
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></TR
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></TABLE
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></DD
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><DT
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><B
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>Arguments and Values</B
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></DT
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><DD
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><P CLASS="j"
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><VAR CLASS="param"
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>instance</VAR
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> — an <A HREF="26_1_Glossary.html#object"
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><EM CLASS="term"
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>object</EM
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></A
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>. </P
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><P CLASS="j"
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><VAR CLASS="param"
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>added-slots</VAR
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> — a <A HREF="26_1_Glossary.html#list"
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><EM CLASS="term"
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|
>list</EM
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></A
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>. </P
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><P CLASS="j"
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><VAR CLASS="param"
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>discarded-slots</VAR
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> — a <A HREF="26_1_Glossary.html#list"
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><EM CLASS="term"
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|
>list</EM
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></A
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>. </P
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><P CLASS="j"
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><VAR CLASS="param"
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>property-list</VAR
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> — a <A HREF="26_1_Glossary.html#list"
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><EM CLASS="term"
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|
>list</EM
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></A
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|
>. </P
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><P CLASS="j"
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><VAR CLASS="param"
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>initargs</VAR
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> — an <A HREF="26_1_Glossary.html#initialization_argument_list"
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><EM CLASS="term"
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|
>initialization argument list</EM
|
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></A
|
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>. </P
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><P CLASS="j"
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|
><VAR CLASS="param"
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>result</VAR
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> — an <A HREF="26_1_Glossary.html#object"
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|
><EM CLASS="term"
|
|
>object</EM
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|
></A
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>.</P
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></DD
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><DT
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><B
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>Description</B
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></DT
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><DD
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><P CLASS="j"
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>The <A HREF="26_1_Glossary.html#generic_function"
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><EM CLASS="term"
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>generic function</EM
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></A
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> <A HREF="f_update-instance-for-redefined-class.html" CLASS="funref"
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><B
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>update-instance-for-redefined-class</B
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></A
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> is not intended to be called by programmers. Programmers may write <A HREF="26_1_Glossary.html#method"
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><EM CLASS="term"
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>methods</EM
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></A
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> for it. The <A HREF="26_1_Glossary.html#generic_function"
|
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><EM CLASS="term"
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>generic function</EM
|
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></A
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> <A HREF="f_update-instance-for-redefined-class.html" CLASS="funref"
|
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><B
|
|
>update-instance-for-redefined-class</B
|
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></A
|
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> is called by the mechanism activated by <A HREF="f_make-instances-obsolete.html" CLASS="funref"
|
|
><B
|
|
>make-instances-obsolete</B
|
|
></A
|
|
>. </P
|
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><P CLASS="j"
|
|
>The system-supplied primary <A HREF="26_1_Glossary.html#method"
|
|
><EM CLASS="term"
|
|
>method</EM
|
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></A
|
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> on <A HREF="f_update-instance-for-redefined-class.html" CLASS="funref"
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><B
|
|
>update-instance-for-redefined-class</B
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></A
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> checks the validity of <VAR CLASS="param"
|
|
>initargs</VAR
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> and signals an error if an <VAR CLASS="param"
|
|
>initarg</VAR
|
|
> is supplied that is not declared as valid. This <A HREF="26_1_Glossary.html#method"
|
|
><EM CLASS="term"
|
|
>method</EM
|
|
></A
|
|
> then initializes <A HREF="26_1_Glossary.html#slot"
|
|
><EM CLASS="term"
|
|
>slots</EM
|
|
></A
|
|
> with values according to the <VAR CLASS="param"
|
|
>initargs</VAR
|
|
>, and initializes the newly <VAR CLASS="param"
|
|
>added-slots</VAR
|
|
> with values according to their <SPAN CLASS="kwd"
|
|
><SPAN CLASS="cmtt"
|
|
>:initform</SPAN
|
|
></SPAN
|
|
> forms. It does this by calling the generic function <A HREF="f_shared-initialize.html" CLASS="funref"
|
|
><B
|
|
>shared-initialize</B
|
|
></A
|
|
> with the following arguments: the <VAR CLASS="param"
|
|
>instance</VAR
|
|
>, a list of names of the newly <VAR CLASS="param"
|
|
>added-slots</VAR
|
|
> to <VAR CLASS="param"
|
|
>instance</VAR
|
|
>, and the <VAR CLASS="param"
|
|
>initargs</VAR
|
|
> it received. Newly <VAR CLASS="param"
|
|
>added-slots</VAR
|
|
> are those <A HREF="26_1_Glossary.html#local_slot"
|
|
><EM CLASS="term"
|
|
>local slots</EM
|
|
></A
|
|
> for which no <A HREF="26_1_Glossary.html#slot"
|
|
><EM CLASS="term"
|
|
>slot</EM
|
|
></A
|
|
> of the same name exists in the old version of the <A HREF="26_1_Glossary.html#class"
|
|
><EM CLASS="term"
|
|
>class</EM
|
|
></A
|
|
>. </P
|
|
><P CLASS="j"
|
|
>When <A HREF="f_make-instances-obsolete.html" CLASS="funref"
|
|
><B
|
|
>make-instances-obsolete</B
|
|
></A
|
|
> is invoked or when a <A HREF="26_1_Glossary.html#class"
|
|
><EM CLASS="term"
|
|
>class</EM
|
|
></A
|
|
> has been redefined and an <A HREF="26_1_Glossary.html#instance"
|
|
><EM CLASS="term"
|
|
>instance</EM
|
|
></A
|
|
> is being updated, a <VAR CLASS="param"
|
|
>property-list</VAR
|
|
> is created that captures the slot names and values of all the <VAR CLASS="param"
|
|
>discarded-slots</VAR
|
|
> with values in the original <VAR CLASS="param"
|
|
>instance</VAR
|
|
>. The structure of the <VAR CLASS="param"
|
|
>instance</VAR
|
|
> is transformed so that it conforms to the current class definition. The arguments to <A HREF="f_update-instance-for-redefined-class.html" CLASS="funref"
|
|
><B
|
|
>update-instance-for-redefined-class</B
|
|
></A
|
|
> are this transformed <VAR CLASS="param"
|
|
>instance</VAR
|
|
>, a list of <VAR CLASS="param"
|
|
>added-slots</VAR
|
|
> to the <VAR CLASS="param"
|
|
>instance</VAR
|
|
>, a list <VAR CLASS="param"
|
|
>discarded-slots</VAR
|
|
> from the <VAR CLASS="param"
|
|
>instance</VAR
|
|
>, and the <VAR CLASS="param"
|
|
>property-list</VAR
|
|
> containing the slot names and values for <A HREF="26_1_Glossary.html#slot"
|
|
><EM CLASS="term"
|
|
>slots</EM
|
|
></A
|
|
> that were discarded and had values. Included in this list of discarded <A HREF="26_1_Glossary.html#slot"
|
|
><EM CLASS="term"
|
|
>slots</EM
|
|
></A
|
|
> are <A HREF="26_1_Glossary.html#slot"
|
|
><EM CLASS="term"
|
|
>slots</EM
|
|
></A
|
|
> that were local in the old <A HREF="26_1_Glossary.html#class"
|
|
><EM CLASS="term"
|
|
>class</EM
|
|
></A
|
|
> and are shared in the new <A HREF="26_1_Glossary.html#class"
|
|
><EM CLASS="term"
|
|
>class</EM
|
|
></A
|
|
>. </P
|
|
><P CLASS="j"
|
|
>The value returned by <A HREF="f_update-instance-for-redefined-class.html" CLASS="funref"
|
|
><B
|
|
>update-instance-for-redefined-class</B
|
|
></A
|
|
> is ignored.</P
|
|
></DD
|
|
><DT
|
|
><B
|
|
>Examples</B
|
|
></DT
|
|
><DD
|
|
><PRE CLASS="screen"
|
|
> (defclass position () ())
|
|
|
|
(defclass x-y-position (position)
|
|
((x :initform 0 :accessor position-x)
|
|
(y :initform 0 :accessor position-y)))
|
|
|
|
;;; It turns out polar coordinates are used more than Cartesian
|
|
;;; coordinates, so the representation is altered and some new
|
|
;;; accessor methods are added.
|
|
|
|
(defmethod update-instance-for-redefined-class :before
|
|
((pos x-y-position) added deleted plist &key)
|
|
;; Transform the x-y coordinates to polar coordinates
|
|
;; and store into the new slots.
|
|
(let ((x (getf plist 'x))
|
|
(y (getf plist 'y)))
|
|
(setf (position-rho pos) (sqrt (+ (* x x) (* y y)))
|
|
(position-theta pos) (atan y x))))
|
|
|
|
(defclass x-y-position (position)
|
|
((rho :initform 0 :accessor position-rho)
|
|
(theta :initform 0 :accessor position-theta)))
|
|
|
|
;;; All instances of the old x-y-position class will be updated
|
|
;;; automatically.
|
|
|
|
;;; The new representation is given the look and feel of the old one.
|
|
|
|
(defmethod position-x ((pos x-y-position))
|
|
(with-slots (rho theta) pos (* rho (cos theta))))
|
|
|
|
(defmethod (setf position-x) (new-x (pos x-y-position))
|
|
(with-slots (rho theta) pos
|
|
(let ((y (position-y pos)))
|
|
(setq rho (sqrt (+ (* new-x new-x) (* y y)))
|
|
theta (atan y new-x))
|
|
new-x)))
|
|
|
|
(defmethod position-y ((pos x-y-position))
|
|
(with-slots (rho theta) pos (* rho (sin theta))))
|
|
|
|
(defmethod (setf position-y) (new-y (pos x-y-position))
|
|
(with-slots (rho theta) pos
|
|
(let ((x (position-x pos)))
|
|
(setq rho (sqrt (+ (* x x) (* new-y new-y)))
|
|
theta (atan new-y x))
|
|
new-y)))</PRE
|
|
></DD
|
|
><DT
|
|
><B
|
|
>Exceptional Situations</B
|
|
></DT
|
|
><DD
|
|
><P CLASS="j"
|
|
>The system-supplied primary <A HREF="26_1_Glossary.html#method"
|
|
><EM CLASS="term"
|
|
>method</EM
|
|
></A
|
|
> on <A HREF="f_update-instance-for-redefined-class.html" CLASS="funref"
|
|
><B
|
|
>update-instance-for-redefined-class</B
|
|
></A
|
|
> signals an error if an <VAR CLASS="param"
|
|
>initarg</VAR
|
|
> is supplied that is not declared as valid.</P
|
|
></DD
|
|
><DT
|
|
><B
|
|
>See Also</B
|
|
></DT
|
|
><DD
|
|
><P CLASS="j"
|
|
><A HREF="f_make-instances-obsolete.html" CLASS="funref"
|
|
><B
|
|
>make-instances-obsolete</B
|
|
></A
|
|
>, <A HREF="f_shared-initialize.html" CLASS="funref"
|
|
><B
|
|
>shared-initialize</B
|
|
></A
|
|
>, <A HREF="4_3_Classes.html#sec_4_3_6" CLASS="secref"
|
|
><SPAN CLASS="cmr"
|
|
>Section</SPAN
|
|
> <SPAN CLASS="cmr"
|
|
>4.3.6</SPAN
|
|
> <SPAN CLASS="cmr"
|
|
>(Redefining</SPAN
|
|
> <SPAN CLASS="cmr"
|
|
>Classes)</SPAN
|
|
></A
|
|
>, <A HREF="7_1_Object_Creation_and_Initialization.html#sec_7_1_4" CLASS="secref"
|
|
><SPAN CLASS="cmr"
|
|
>Section</SPAN
|
|
> <SPAN CLASS="cmr"
|
|
>7.1.4</SPAN
|
|
> <SPAN CLASS="cmr"
|
|
>(Rules</SPAN
|
|
> <SPAN CLASS="cmr"
|
|
>for</SPAN
|
|
> <SPAN CLASS="cmr"
|
|
>Initialization</SPAN
|
|
> <SPAN CLASS="cmr"
|
|
>Arguments)</SPAN
|
|
></A
|
|
>, <A HREF="7_1_Object_Creation_and_Initialization.html#sec_7_1_2" CLASS="secref"
|
|
><SPAN CLASS="cmr"
|
|
>Section</SPAN
|
|
> <SPAN CLASS="cmr"
|
|
>7.1.2</SPAN
|
|
> <SPAN CLASS="cmr"
|
|
>(Declaring</SPAN
|
|
> <SPAN CLASS="cmr"
|
|
>the</SPAN
|
|
> <SPAN CLASS="cmr"
|
|
>Validity</SPAN
|
|
> <SPAN CLASS="cmr"
|
|
>of</SPAN
|
|
> <SPAN CLASS="cmr"
|
|
>Initialization</SPAN
|
|
> <SPAN CLASS="cmr"
|
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