79 lines
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79 lines
5.7 KiB
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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: Accessor VALUES</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="m_mult_2.htm"><IMG WIDTH=40 HEIGHT=40 ALT="[Previous]" SRC="../Graphics/Prev.gif" ALIGN=Bottom></A><A REL=UP HREF="c_data_a.htm"><IMG WIDTH=40 HEIGHT=40 ALT="[Up]" SRC="../Graphics/Up.gif" ALIGN=Bottom></A><A REL=NEXT HREF="f_vals_l.htm"><IMG WIDTH=40 HEIGHT=40 ALT="[Next]" SRC="../Graphics/Next.gif" ALIGN=Bottom></A></H1>
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<A NAME="values"><I>Accessor</I> <B>VALUES</B></A> <P>
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<P><B>Syntax:</B><P>
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<P>
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<B>values</B> <I><TT>&rest</TT> object</I> => <I><I>object</I><B>*</B></I><P>
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<TT>(setf (</TT><B>values</B> <I><TT>&rest</TT> place</I><TT>) </TT><I>new-values</I><TT>)</TT><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>object</I>---an <A REL=DEFINITION HREF="26_glo_o.htm#object"><I>object</I></A>. <P>
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<I>place</I>---a <A REL=DEFINITION HREF="26_glo_p.htm#place"><I>place</I></A>. <P>
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<I>new-value</I>---an <A REL=DEFINITION HREF="26_glo_o.htm#object"><I>object</I></A>. <P>
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<P><B>Description:</B><P>
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<P>
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<A REL=DEFINITION HREF="#values"><B>values</B></A> returns the <I>objects</I> as <A REL=DEFINITION HREF="26_glo_m.htm#multiple_values"><I>multiple values</I></A>[2]. <P>
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<A REL=DEFINITION HREF="m_setf_.htm#setf"><B>setf</B></A> of <A REL=DEFINITION HREF="#values"><B>values</B></A> is used to store the <A REL=DEFINITION HREF="26_glo_m.htm#multiple_values"><I>multiple values</I></A>[2] <I>new-values</I> into the <I>places</I>. See <A REL=CHILD HREF="05_abc.htm">Section 5.1.2.3 (VALUES Forms as Places)</A>. <P>
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<P><B>Examples:</B><P>
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<P>
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<PRE>
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(values) => <no values>
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(values 1) => 1
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(values 1 2) => 1, 2
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(values 1 2 3) => 1, 2, 3
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(values (values 1 2 3) 4 5) => 1, 4, 5
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(defun polar (x y)
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(values (sqrt (+ (* x x) (* y y))) (atan y x))) => POLAR
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(multiple-value-bind (r theta) (polar 3.0 4.0)
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(vector r theta))
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=> #(5.0 0.927295)
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</PRE>
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</TT> <P>
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Sometimes it is desirable to indicate explicitly that a function returns exactly one value. For example, the function <P>
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<PRE>
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(defun foo (x y)
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(floor (+ x y) y)) => FOO
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</PRE>
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</TT> returns two values because <A REL=DEFINITION HREF="f_floorc.htm#floor"><B>floor</B></A> returns two values. It may be that the second value makes no sense, or that for efficiency reasons it is desired not to compute the second value. <A REL=DEFINITION HREF="#values"><B>values</B></A> is the standard idiom for indicating that only one value is to be returned: <P>
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<PRE>
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(defun foo (x y)
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(values (floor (+ x y) y))) => FOO
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</PRE>
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</TT> This works because <A REL=DEFINITION HREF="#values"><B>values</B></A> returns exactly one value for each of <I>args</I>; as for any function call, if any of <I>args</I> produces more than one value, all but the first are discarded. <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_vals_l.htm#values-list"><B>values-list</B></A>, <A REL=DEFINITION HREF="m_multip.htm#multiple-value-bind"><B>multiple-value-bind</B></A>, <A REL=DEFINITION HREF="v_multip.htm#multiple-values-limit"><B>multiple-values-limit</B></A>, <A REL=CHILD HREF="03_a.htm">Section 3.1 (Evaluation)</A> <P>
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<P><B>Notes:</B><P>
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<P>
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Since <A REL=DEFINITION HREF="#values"><B>values</B></A> is a <A REL=DEFINITION HREF="26_glo_f.htm#function"><I>function</I></A>, not a <A REL=DEFINITION HREF="26_glo_m.htm#macro"><I>macro</I></A> or <A REL=DEFINITION HREF="26_glo_s.htm#special_form"><I>special form</I></A>, it receives as <A REL=DEFINITION HREF="26_glo_a.htm#argument"><I>arguments</I></A> only the <A REL=DEFINITION HREF="26_glo_p.htm#primary_value"><I>primary values</I></A> of its <A REL=DEFINITION HREF="26_glo_a.htm#argument"><I>argument</I></A> <A REL=DEFINITION HREF="26_glo_f.htm#form"><I>forms</I></A>. <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/iss311.htm">SETF-OF-VALUES:ADD</A><P></UL><HR>
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