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39 lines
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<TITLE>CLHS: Section 3.1.7</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="03_af.htm"><IMG WIDTH=40 HEIGHT=40 ALT="[Previous]" SRC="../Graphics/Prev.gif" ALIGN=Bottom></A><A REL=UP HREF="03_a.htm"><IMG WIDTH=40 HEIGHT=40 ALT="[Up]" SRC="../Graphics/Up.gif" ALIGN=Bottom></A><A REL=NEXT HREF="03_b.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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3.1.7 Return Values</H2> <P>
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Ordinarily the result of calling a <A REL=DEFINITION HREF="26_glo_f.htm#function"><I>function</I></A> is a single <A REL=DEFINITION HREF="26_glo_o.htm#object"><I>object</I></A>. Sometimes, however, it is convenient for a function to compute several <A REL=DEFINITION HREF="26_glo_o.htm#object"><I>objects</I></A> and return them. <P>
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In order to receive other than exactly one value from a <A REL=DEFINITION HREF="26_glo_f.htm#form"><I>form</I></A>, one of several <A REL=DEFINITION HREF="26_glo_s.htm#special_form"><I>special forms</I></A> or <A REL=DEFINITION HREF="26_glo_m.htm#macro"><I>macros</I></A> must be used to request those values. If a <A REL=DEFINITION HREF="26_glo_f.htm#form"><I>form</I></A> produces <A REL=DEFINITION HREF="26_glo_m.htm#multiple_values"><I>multiple values</I></A> which were not requested in this way, then the first value is given to the caller and all others are discarded; if the <A REL=DEFINITION HREF="26_glo_f.htm#form"><I>form</I></A> produces zero values, then the caller receives <A REL=DEFINITION HREF="a_nil.htm#nil"><B>nil</B></A> as a value. <P>
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The next figure lists some <A REL=DEFINITION HREF="26_glo_o.htm#operator"><I>operators</I></A> for receiving <A REL=DEFINITION HREF="26_glo_m.htm#multiple_values"><I>multiple values</I></A>[2]. These <A REL=DEFINITION HREF="26_glo_o.htm#operator"><I>operators</I></A> can be used to specify one or more <A REL=DEFINITION HREF="26_glo_f.htm#form"><I>forms</I></A> to <A REL=DEFINITION HREF="26_glo_e.htm#evaluate"><I>evaluate</I></A> and where to put the <A REL=DEFINITION HREF="26_glo_v.htm#value"><I>values</I></A> returned by those <A REL=DEFINITION HREF="26_glo_f.htm#form"><I>forms</I></A>. <P>
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<PRE>
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<A REL=DEFINITION HREF="m_multip.htm#multiple-value-bind">multiple-value-bind</A> <A REL=DEFINITION HREF="s_mult_1.htm#multiple-value-prog1">multiple-value-prog1</A> <A REL=DEFINITION HREF="s_ret_fr.htm#return-from">return-from</A>
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<A REL=DEFINITION HREF="s_multip.htm#multiple-value-call">multiple-value-call</A> <A REL=DEFINITION HREF="m_mult_2.htm#multiple-value-setq">multiple-value-setq</A> <A REL=DEFINITION HREF="s_throw.htm#throw">throw</A>
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<A REL=DEFINITION HREF="m_mult_1.htm#multiple-value-list">multiple-value-list</A> <A REL=DEFINITION HREF="m_return.htm#return">return</A>
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</PRE>
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<P><B>Figure 3-5. Some operators applicable to receiving multiple values</B> <P>
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The <A REL=DEFINITION HREF="26_glo_f.htm#function"><I>function</I></A> <A REL=DEFINITION HREF="f_values.htm#values"><B>values</B></A> can produce <A REL=DEFINITION HREF="26_glo_m.htm#multiple_values"><I>multiple values</I></A>[2]. <TT>(values)</TT> returns zero values; <TT>(values </TT><I>form</I><TT>)</TT> returns the <A REL=DEFINITION HREF="26_glo_p.htm#primary_value"><I>primary value</I></A> returned by <I>form</I>; <TT>(values </TT><I>form1</I><TT> </TT><I>form2</I><TT>)</TT> returns two values, the <A REL=DEFINITION HREF="26_glo_p.htm#primary_value"><I>primary value</I></A> of <I>form1</I> and the <A REL=DEFINITION HREF="26_glo_p.htm#primary_value"><I>primary value</I></A> of <I>form2</I>; and so on. <P>
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See <A REL=DEFINITION HREF="v_multip.htm#multiple-values-limit"><B>multiple-values-limit</B></A> and <A REL=DEFINITION HREF="f_vals_l.htm#values-list"><B>values-list</B></A>. <P>
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