72 lines
4.3 KiB
HTML
72 lines
4.3 KiB
HTML
|
<!-- Common Lisp HyperSpec (TM), version 7.0 generated by Kent M. Pitman on Mon, 11-Apr-2005 2:31am EDT -->
|
||
|
|
<HTML>
|
||
|
|
<HEAD>
|
||
|
|
<TITLE>CLHS: Macro NTH-VALUE</TITLE>
|
||
|
|
<LINK HREF="../Data/clhs.css" REL="stylesheet" TYPE="text/css" />
|
||
|
|
<META HTTP-EQUIV="Author" CONTENT="Kent M. Pitman">
|
||
|
|
<META HTTP-EQUIV="Organization" CONTENT="LispWorks Ltd.">
|
||
|
|
<LINK REL=TOP HREF="../Front/index.htm">
|
||
|
|
<LINK REL=COPYRIGHT HREF="../Front/Help.htm#Legal">
|
||
|
|
<LINK REL=DISCLAIMER HREF="../Front/Help.htm#Disclaimer">
|
||
|
|
<LINK REL=PREV HREF="v_multip.htm">
|
||
|
|
<LINK REL=UP HREF="c_data_a.htm">
|
||
|
|
<LINK REL=NEXT HREF="m_prog_.htm">
|
||
|
|
</HEAD>
|
||
|
|
<BODY>
|
||
|
|
<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="v_multip.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="m_prog_.htm"><IMG WIDTH=40 HEIGHT=40 ALT="[Next]" SRC="../Graphics/Next.gif" ALIGN=Bottom></A></H1>
|
||
|
|
|
||
|
|
<HR>
|
||
|
|
|
||
|
|
<A NAME="nth-value"><I>Macro</I> <B>NTH-VALUE</B></A> <P>
|
||
|
|
<P>
|
||
|
|
<P><B>Syntax:</B><P>
|
||
|
|
<P>
|
||
|
|
|
||
|
|
<B>nth-value</B> <I>n form</I> => <I>object</I><P>
|
||
|
|
<P>
|
||
|
|
<P><B>Arguments and Values:</B><P>
|
||
|
|
<P>
|
||
|
|
<I>n</I>---a non-negative <A REL=DEFINITION HREF="26_glo_i.htm#integer"><I>integer</I></A>; evaluated. <P>
|
||
|
|
<I>form</I>---a <A REL=DEFINITION HREF="26_glo_f.htm#form"><I>form</I></A>; evaluated as described below. <P>
|
||
|
|
<I>object</I>---an <A REL=DEFINITION HREF="26_glo_o.htm#object"><I>object</I></A>. <P>
|
||
|
|
<P><B>Description:</B><P>
|
||
|
|
<P>
|
||
|
|
Evaluates <I>n</I> and then <I>form</I>, returning as its only value the <I>n</I>th value <I>yielded</I> by <I>form</I>, or <A REL=DEFINITION HREF="a_nil.htm#nil"><B>nil</B></A> if <I>n</I> is greater than or equal to the number of <A REL=DEFINITION HREF="26_glo_v.htm#value"><I>values</I></A> returned by <I>form</I>. (The first returned value is numbered <TT>0</TT>.) <P>
|
||
|
|
<P><B>Examples:</B><P>
|
||
|
|
<P>
|
||
|
|
<PRE>
|
||
|
|
(nth-value 0 (values 'a 'b)) => A
|
||
|
|
(nth-value 1 (values 'a 'b)) => B
|
||
|
|
(nth-value 2 (values 'a 'b)) => NIL
|
||
|
|
(let* ((x 83927472397238947423879243432432432)
|
||
|
|
(y 32423489732)
|
||
|
|
(a (nth-value 1 (floor x y)))
|
||
|
|
(b (mod x y)))
|
||
|
|
(values a b (= a b)))
|
||
|
|
=> 3332987528, 3332987528, <A REL=DEFINITION HREF="26_glo_t.htm#true">true</A>
|
||
|
|
</PRE>
|
||
|
|
</TT> <P>
|
||
|
|
<P><B>Side Effects:</B> None.
|
||
|
|
<P>
|
||
|
|
<P><B>Affected By:</B> None.
|
||
|
|
<P>
|
||
|
|
<P><B>Exceptional Situations:</B> None.
|
||
|
|
<P>
|
||
|
|
<P><B>See Also:</B><P>
|
||
|
|
<P>
|
||
|
|
<A REL=DEFINITION HREF="m_mult_1.htm#multiple-value-list"><B>multiple-value-list</B></A>, <A REL=DEFINITION HREF="f_nth.htm#nth"><B>nth</B></A> <P>
|
||
|
|
<P><B>Notes:</B><P>
|
||
|
|
<P>
|
||
|
|
Operationally, the following relationship is true, although <A REL=DEFINITION HREF="#nth-value"><B>nth-value</B></A> might be more efficient in some <A REL=DEFINITION HREF="26_glo_i.htm#implementation"><I>implementations</I></A> because, for example, some <I>consing</I> might be avoided. <P>
|
||
|
|
<PRE>
|
||
|
|
(nth-value n form) == (nth n (multiple-value-list form))
|
||
|
|
</PRE>
|
||
|
|
</TT> <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/iss250.htm">NTH-VALUE:ADD</A><P></UL><HR>
|
||
|
|
|
||
|
|
<A REL=NAVIGATOR HREF="../Front/StartPts.htm"><IMG WIDTH=80 HEIGHT=40 ALT="[Starting Points]" SRC="../Graphics/StartPts.gif" ALIGN=Bottom></A><A REL=TOC HREF="../Front/Contents.htm"><IMG WIDTH=80 HEIGHT=40 ALT="[Contents]" SRC="../Graphics/Contents.gif" ALIGN=Bottom></A><A REL=INDEX HREF="../Front/X_Master.htm"><IMG WIDTH=80 HEIGHT=40 ALT="[Index]" SRC="../Graphics/Index.gif" ALIGN=Bottom></A><A REL=INDEX HREF="../Front/X_Symbol.htm"><IMG WIDTH=80 HEIGHT=40 ALT="[Symbols]" SRC="../Graphics/Symbols.gif" ALIGN=Bottom></A><A REL=GLOSSARY HREF="../Body/26_a.htm"><IMG WIDTH=80 HEIGHT=40 ALT="[Glossary]" SRC="../Graphics/Glossary.gif" ALIGN=Bottom></A><A HREF="../Front/X3J13Iss.htm"><IMG WIDTH=80 HEIGHT=40 ALT="[Issues]" SRC="../Graphics/Issues.gif" ALIGN=Bottom></A><BR>
|
||
|
|
|
||
|
|
<A REL=COPYRIGHT HREF="../Front/Help.htm#Legal"><I>Copyright 1996-2005, LispWorks Ltd. All rights reserved.</I></A><P>
|
||
|
|
</BODY>
|
||
|
|
</HTML>
|