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<TITLE>CLHS: Section 7.6.6</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="07_fea.htm"><IMG WIDTH=40 HEIGHT=40 ALT="[Previous]" SRC="../Graphics/Prev.gif" ALIGN=Bottom></A><A REL=UP HREF="07_f.htm"><IMG WIDTH=40 HEIGHT=40 ALT="[Up]" SRC="../Graphics/Up.gif" ALIGN=Bottom></A><A REL=NEXT HREF="07_ffa.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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7.6.6 Method Selection and Combination</H2> <P>
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When a <A REL=DEFINITION HREF="26_glo_g.htm#generic_function"><I>generic function</I></A> is called with particular arguments, it must determine the code to execute. This code is called the <A REL=DEFINITION HREF="26_glo_e.htm#effective_method"><I>effective method</I></A> for those <A REL=DEFINITION HREF="26_glo_a.htm#argument"><I>arguments</I></A>. The <A REL=DEFINITION HREF="26_glo_e.htm#effective_method"><I>effective method</I></A> is a combination of the <A REL=DEFINITION HREF="26_glo_a.htm#applicable_method"><I>applicable methods</I></A> in the <A REL=DEFINITION HREF="26_glo_g.htm#generic_function"><I>generic function</I></A> that <A REL=DEFINITION HREF="26_glo_c.htm#call"><I>calls</I></A> some or all of the <A REL=DEFINITION HREF="26_glo_m.htm#method"><I>methods</I></A>. <P>
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If a <A REL=DEFINITION HREF="26_glo_g.htm#generic_function"><I>generic function</I></A> is called and no <A REL=DEFINITION HREF="26_glo_m.htm#method"><I>methods</I></A> are <A REL=DEFINITION HREF="26_glo_a.htm#applicable"><I>applicable</I></A>, the <A REL=DEFINITION HREF="26_glo_g.htm#generic_function"><I>generic function</I></A> <A REL=DEFINITION HREF="f_no_app.htm#no-applicable-method"><B>no-applicable-method</B></A> is invoked, with the <I>results</I> from that call being used as the <I>results</I> of the call to the original <A REL=DEFINITION HREF="26_glo_g.htm#generic_function"><I>generic function</I></A>. Calling <A REL=DEFINITION HREF="f_no_app.htm#no-applicable-method"><B>no-applicable-method</B></A> takes precedence over checking for acceptable keyword arguments; see <A REL=CHILD HREF="07_fe.htm">Section 7.6.5 (Keyword Arguments in Generic Functions and Methods)</A>. <P>
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When the <A REL=DEFINITION HREF="26_glo_e.htm#effective_method"><I>effective method</I></A> has been determined, it is invoked with the same <A REL=DEFINITION HREF="26_glo_a.htm#argument"><I>arguments</I></A> as were passed to the <A REL=DEFINITION HREF="26_glo_g.htm#generic_function"><I>generic function</I></A>. Whatever <A REL=DEFINITION HREF="26_glo_v.htm#value"><I>values</I></A> it returns are returned as the <A REL=DEFINITION HREF="26_glo_v.htm#value"><I>values</I></A> of the <A REL=DEFINITION HREF="26_glo_g.htm#generic_function"><I>generic function</I></A>. <P>
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<A REL=CHILD HREF="07_ffa.htm"><H2>
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7.6.6.1 Determining the Effective Method</H2></A><P>
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<A REL=CHILD HREF="07_ffb.htm"><H2>
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7.6.6.2 Standard Method Combination</H2></A><P>
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<A REL=CHILD HREF="07_ffc.htm"><H2>
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7.6.6.3 Declarative Method Combination</H2></A><P>
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<A REL=CHILD HREF="07_ffd.htm"><H2>
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7.6.6.4 Built-in Method Combination Types</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/iss050.htm">CLOS-ERROR-CHECKING-ORDER:NO-APPLICABLE-METHOD-FIRST</A><P></UL><HR>
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