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46 lines
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<TITLE>CLHS: Section 4.3.2</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="04_caa.htm"><IMG WIDTH=40 HEIGHT=40 ALT="[Previous]" SRC="../Graphics/Prev.gif" ALIGN=Bottom></A><A REL=UP HREF="04_c.htm"><IMG WIDTH=40 HEIGHT=40 ALT="[Up]" SRC="../Graphics/Up.gif" ALIGN=Bottom></A><A REL=NEXT HREF="04_cc.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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4.3.2 Defining Classes</H2> <P>
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The macro <A REL=DEFINITION HREF="m_defcla.htm#defclass"><B>defclass</B></A> is used to define a new named <A REL=DEFINITION HREF="26_glo_c.htm#class"><I>class</I></A>. <P>
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The definition of a <A REL=DEFINITION HREF="26_glo_c.htm#class"><I>class</I></A> includes: <P>
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<P><DL><P>
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<DT>* The <A REL=DEFINITION HREF="26_glo_n.htm#name"><I>name</I></A> of the new <A REL=DEFINITION HREF="26_glo_c.htm#class"><I>class</I></A>. For newly-defined <A REL=DEFINITION HREF="26_glo_c.htm#class"><I>classes</I></A> this <A REL=DEFINITION HREF="26_glo_n.htm#name"><I>name</I></A> is a <A REL=DEFINITION HREF="26_glo_p.htm#proper_name"><I>proper name</I></A>. <P><DD>
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<DT>* The list of the direct <A REL=DEFINITION HREF="26_glo_s.htm#superclass"><I>superclasses</I></A> of the new <A REL=DEFINITION HREF="26_glo_c.htm#class"><I>class</I></A>. <P><DD>
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<DT>* A set of <A REL=DEFINITION HREF="26_glo_s.htm#slot_specifier"><I>slot specifiers</I></A>. Each <A REL=DEFINITION HREF="26_glo_s.htm#slot_specifier"><I>slot specifier</I></A> includes the <A REL=DEFINITION HREF="26_glo_n.htm#name"><I>name</I></A> of the <A REL=DEFINITION HREF="26_glo_s.htm#slot"><I>slot</I></A> and zero or more <A REL=DEFINITION HREF="26_glo_s.htm#slot"><I>slot</I></A> options. A <A REL=DEFINITION HREF="26_glo_s.htm#slot"><I>slot</I></A> option pertains only to a single <A REL=DEFINITION HREF="26_glo_s.htm#slot"><I>slot</I></A>. If a <A REL=DEFINITION HREF="26_glo_c.htm#class"><I>class</I></A> definition contains two <A REL=DEFINITION HREF="26_glo_s.htm#slot_specifier"><I>slot specifiers</I></A> with the same <A REL=DEFINITION HREF="26_glo_n.htm#name"><I>name</I></A>, an error is signaled. <P><DD>
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<DT>* A set of <A REL=DEFINITION HREF="26_glo_c.htm#class"><I>class</I></A> options. Each <A REL=DEFINITION HREF="26_glo_c.htm#class"><I>class</I></A> option pertains to the <A REL=DEFINITION HREF="26_glo_c.htm#class"><I>class</I></A> as a whole. <P><DD>
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<P></DL><P>
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The <A REL=DEFINITION HREF="26_glo_s.htm#slot"><I>slot</I></A> options and <A REL=DEFINITION HREF="26_glo_c.htm#class"><I>class</I></A> options of the <A REL=DEFINITION HREF="m_defcla.htm#defclass"><B>defclass</B></A> form provide mechanisms for the following: <P>
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<P><DL><P>
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<DT>* Supplying a default initial value <A REL=DEFINITION HREF="26_glo_f.htm#form"><I>form</I></A> for a given <A REL=DEFINITION HREF="26_glo_s.htm#slot"><I>slot</I></A>. <P><DD>
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<DT>* Requesting that <A REL=DEFINITION HREF="26_glo_m.htm#method"><I>methods</I></A> for <A REL=DEFINITION HREF="26_glo_g.htm#generic_function"><I>generic functions</I></A> be automatically generated for reading or writing <A REL=DEFINITION HREF="26_glo_s.htm#slot"><I>slots</I></A>. <P><DD>
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<DT>* Controlling whether a given <A REL=DEFINITION HREF="26_glo_s.htm#slot"><I>slot</I></A> is shared by all <A REL=DEFINITION HREF="26_glo_i.htm#instance"><I>instances</I></A> of the <A REL=DEFINITION HREF="26_glo_c.htm#class"><I>class</I></A> or whether each <A REL=DEFINITION HREF="26_glo_i.htm#instance"><I>instance</I></A> of the <A REL=DEFINITION HREF="26_glo_c.htm#class"><I>class</I></A> has its own <A REL=DEFINITION HREF="26_glo_s.htm#slot"><I>slot</I></A>. <P><DD>
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<DT>* Supplying a set of initialization arguments and initialization argument defaults to be used in <A REL=DEFINITION HREF="26_glo_i.htm#instance"><I>instance</I></A> creation. <P><DD>
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<DT>* Indicating that the <A REL=DEFINITION HREF="26_glo_m.htm#metaclass"><I>metaclass</I></A> is to be other than the default. The <TT>:metaclass</TT> option is reserved for future use; an implementation can be extended to make use of the <TT>:metaclass</TT> option. <P><DD>
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<DT>* Indicating the expected <A REL=DEFINITION HREF="26_glo_t.htm#type"><I>type</I></A> for the value stored in the <A REL=DEFINITION HREF="26_glo_s.htm#slot"><I>slot</I></A>. <P><DD>
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<DT>* Indicating the <A REL=DEFINITION HREF="26_glo_d.htm#documentation_string"><I>documentation string</I></A> for the <A REL=DEFINITION HREF="26_glo_s.htm#slot"><I>slot</I></A>. <P><DD>
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