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61 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: Local Macro CALL-METHOD, MAKE-METHOD</TITLE>
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<A NAME="call-method"><A NAME="make-method"><I>Local Macro</I> <B>CALL-METHOD, MAKE-METHOD</B></A></A> <P>
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<P><B>Syntax:</B><P>
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<P>
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<B>call-method</B> <I>method <TT>&optional</TT> next-method-list</I> => <I><I>result</I><B>*</B></I><P>
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<B>make-method</B> <I>form</I> => <I>method-object</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>method</I>---a <A REL=DEFINITION HREF="26_glo_m.htm#method"><I>method</I></A> <A REL=DEFINITION HREF="26_glo_o.htm#object"><I>object</I></A>, or a <A REL=DEFINITION HREF="26_glo_l.htm#list"><I>list</I></A> (see below); not evaluated. <P>
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<I>method-object</I>---a <A REL=DEFINITION HREF="26_glo_m.htm#method"><I>method</I></A> <A REL=DEFINITION HREF="26_glo_o.htm#object"><I>object</I></A>. <P>
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<I>next-method-list</I>---a <A REL=DEFINITION HREF="26_glo_l.htm#list"><I>list</I></A> of <I>method</I> <A REL=DEFINITION HREF="26_glo_o.htm#object"><I>objects</I></A>; not evaluated. <P>
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<I>results</I>---the <A REL=DEFINITION HREF="26_glo_v.htm#value"><I>values</I></A> returned by the <A REL=DEFINITION HREF="26_glo_m.htm#method"><I>method</I></A> invocation. <P>
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<P><B>Description:</B><P>
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<P>
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The macro <A REL=DEFINITION HREF="#call-method"><B>call-method</B></A> is used in method combination. It hides the <A REL=DEFINITION HREF="26_glo_i.htm#implementation-dependent"><I>implementation-dependent</I></A> details of how <A REL=DEFINITION HREF="26_glo_m.htm#method"><I>methods</I></A> are called. The macro <A REL=DEFINITION HREF="#call-method"><B>call-method</B></A> has <A REL=DEFINITION HREF="26_glo_l.htm#lexical_scope"><I>lexical scope</I></A> and can only be used within an <A REL=DEFINITION HREF="26_glo_e.htm#effective_method"><I>effective method</I></A> <A REL=DEFINITION HREF="26_glo_f.htm#form"><I>form</I></A>. <P>
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Whether or not <A REL=DEFINITION HREF="#call-method"><B>call-method</B></A> is <A REL=DEFINITION HREF="26_glo_f.htm#fbound"><I>fbound</I></A> in the <A REL=DEFINITION HREF="26_glo_g.htm#global_environment"><I>global environment</I></A> is <A REL=DEFINITION HREF="26_glo_i.htm#implementation-dependent"><I>implementation-dependent</I></A>; however, the restrictions on redefinition and <I>shadowing</I> of <A REL=DEFINITION HREF="#call-method"><B>call-method</B></A> are the same as for <A REL=DEFINITION HREF="26_glo_s.htm#symbol"><I>symbols</I></A> in the <TT>COMMON-LISP</TT> package which are <A REL=DEFINITION HREF="26_glo_f.htm#fbound"><I>fbound</I></A> in the <A REL=DEFINITION HREF="26_glo_g.htm#global_environment"><I>global environment</I></A>. The consequences of attempting to use <A REL=DEFINITION HREF="#call-method"><B>call-method</B></A> outside of an <A REL=DEFINITION HREF="26_glo_e.htm#effective_method"><I>effective method</I></A> <A REL=DEFINITION HREF="26_glo_f.htm#form"><I>form</I></A> are undefined. <P>
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The macro <A REL=DEFINITION HREF="#call-method"><B>call-method</B></A> invokes the specified <A REL=DEFINITION HREF="26_glo_m.htm#method"><I>method</I></A>, supplying it with arguments and with definitions for <A REL=DEFINITION HREF="f_call_n.htm#call-next-method"><B>call-next-method</B></A> and for <A REL=DEFINITION HREF="f_next_m.htm#next-method-p"><B>next-method-p</B></A>. If the invocation of <A REL=DEFINITION HREF="#call-method"><B>call-method</B></A> is lexically inside of a <A REL=DEFINITION HREF="#make-method"><B>make-method</B></A>, the arguments are those that were supplied to that method. Otherwise the arguments are those that were supplied to the generic function. The definitions of <A REL=DEFINITION HREF="f_call_n.htm#call-next-method"><B>call-next-method</B></A> and <A REL=DEFINITION HREF="f_next_m.htm#next-method-p"><B>next-method-p</B></A> rely on the specified <I>next-method-list</I>. <P>
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If <I>method</I> is a <A REL=DEFINITION HREF="26_glo_l.htm#list"><I>list</I></A>, the first element of the <A REL=DEFINITION HREF="26_glo_l.htm#list"><I>list</I></A> must be the symbol <A REL=DEFINITION HREF="#make-method"><B>make-method</B></A> and the second element must be a <A REL=DEFINITION HREF="26_glo_f.htm#form"><I>form</I></A>. Such a <A REL=DEFINITION HREF="26_glo_l.htm#list"><I>list</I></A> specifies a <A REL=DEFINITION HREF="26_glo_m.htm#method"><I>method</I></A> <A REL=DEFINITION HREF="26_glo_o.htm#object"><I>object</I></A> whose <A REL=DEFINITION HREF="26_glo_m.htm#method"><I>method</I></A> function has a body that is the given <A REL=DEFINITION HREF="26_glo_f.htm#form"><I>form</I></A>. <P>
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<I>Next-method-list</I> can contain <A REL=DEFINITION HREF="26_glo_m.htm#method"><I>method</I></A> <A REL=DEFINITION HREF="26_glo_o.htm#object"><I>objects</I></A> or <A REL=DEFINITION HREF="26_glo_l.htm#list"><I>lists</I></A>, the first element of which must be the symbol <A REL=DEFINITION HREF="#make-method"><B>make-method</B></A> and the second element of which must be a <A REL=DEFINITION HREF="26_glo_f.htm#form"><I>form</I></A>. <P>
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Those are the only two places where <A REL=DEFINITION HREF="#make-method"><B>make-method</B></A> can be used. The <A REL=DEFINITION HREF="26_glo_f.htm#form"><I>form</I></A> used with <A REL=DEFINITION HREF="#make-method"><B>make-method</B></A> is evaluated in the <A REL=DEFINITION HREF="26_glo_n.htm#null_lexical_environment"><I>null lexical environment</I></A> augmented with a local macro definition for <A REL=DEFINITION HREF="#call-method"><B>call-method</B></A> and with bindings named by symbols not <A REL=DEFINITION HREF="26_glo_a.htm#accessible"><I>accessible</I></A> from the <TT>COMMON-LISP-USER</TT> package. <P>
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The <A REL=DEFINITION HREF="f_call_n.htm#call-next-method"><B>call-next-method</B></A> function available to <I>method</I> will call the first <A REL=DEFINITION HREF="26_glo_m.htm#method"><I>method</I></A> in <I>next-method-list</I>. The <A REL=DEFINITION HREF="f_call_n.htm#call-next-method"><B>call-next-method</B></A> function available in that <A REL=DEFINITION HREF="26_glo_m.htm#method"><I>method</I></A>, in turn, will call the second <A REL=DEFINITION HREF="26_glo_m.htm#method"><I>method</I></A> in <I>next-method-list</I>, and so on, until the list of next <A REL=DEFINITION HREF="26_glo_m.htm#method"><I>methods</I></A> is exhausted. <P>
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If <I>next-method-list</I> is not supplied, the <A REL=DEFINITION HREF="f_call_n.htm#call-next-method"><B>call-next-method</B></A> function available to <I>method</I> signals an error of <A REL=DEFINITION HREF="26_glo_t.htm#type"><I>type</I></A> <A REL=DEFINITION HREF="e_contro.htm#control-error"><B>control-error</B></A> and the <A REL=DEFINITION HREF="f_next_m.htm#next-method-p"><B>next-method-p</B></A> function available to <I>method</I> returns <A REL=DEFINITION HREF="a_nil.htm#nil"><B>nil</B></A>. <P>
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<P><B>Examples:</B><P>
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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> None.
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<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_call_n.htm#call-next-method"><B>call-next-method</B></A>, <A REL=DEFINITION HREF="m_defi_4.htm#define-method-combination"><B>define-method-combination</B></A>, <A REL=DEFINITION HREF="f_next_m.htm#next-method-p"><B>next-method-p</B></A> <P>
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<P><B>Notes:</B> None.
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<P>
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<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/iss211.htm">LEXICAL-CONSTRUCT-GLOBAL-DEFINITION:UNDEFINED</A><P></UL><HR>
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