78 lines
6.9 KiB
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78 lines
6.9 KiB
HTML
<!-- 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: Macro DOLIST</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_dotime.htm"><IMG WIDTH=40 HEIGHT=40 ALT="[Previous]" SRC="../Graphics/Prev.gif" ALIGN=Bottom></A><A REL=UP HREF="c_iterat.htm"><IMG WIDTH=40 HEIGHT=40 ALT="[Up]" SRC="../Graphics/Up.gif" ALIGN=Bottom></A><A REL=NEXT HREF="m_loop.htm"><IMG WIDTH=40 HEIGHT=40 ALT="[Next]" SRC="../Graphics/Next.gif" ALIGN=Bottom></A></H1>
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<HR>
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<A NAME="dolist"><I>Macro</I> <B>DOLIST</B></A> <P>
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<P>
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<P><B>Syntax:</B><P>
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<P>
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<B>dolist</B> <I>(var list-form [result-form]) <I>declaration</I><B>*</B> {tag | statement}*</I><P> => <I><I>result</I><B>*</B></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>var</I>---a <A REL=DEFINITION HREF="26_glo_s.htm#symbol"><I>symbol</I></A>. <P>
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<I>list-form</I>---a <A REL=DEFINITION HREF="26_glo_f.htm#form"><I>form</I></A>. <P>
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<I>result-form</I>---a <A REL=DEFINITION HREF="26_glo_f.htm#form"><I>form</I></A>. <P>
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<I>declaration</I>---a <A REL=DEFINITION HREF="s_declar.htm#declare"><B>declare</B></A> <A REL=DEFINITION HREF="26_glo_e.htm#expression"><I>expression</I></A>; not evaluated. <P>
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<I>tag</I>---a <A REL=DEFINITION HREF="26_glo_g.htm#go_tag"><I>go tag</I></A>; not evaluated. <P>
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<I>statement</I>---a <A REL=DEFINITION HREF="26_glo_c.htm#compound_form"><I>compound form</I></A>; evaluated as described below. <P>
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<I>results</I>---if a <A REL=DEFINITION HREF="m_return.htm#return"><B>return</B></A> or <A REL=DEFINITION HREF="s_ret_fr.htm#return-from"><B>return-from</B></A> form is executed, the <A REL=DEFINITION HREF="26_glo_v.htm#value"><I>values</I></A> passed from that <A REL=DEFINITION HREF="26_glo_f.htm#form"><I>form</I></A>; otherwise, the <A REL=DEFINITION HREF="26_glo_v.htm#value"><I>values</I></A> returned by the <I>result-form</I> or <A REL=DEFINITION HREF="a_nil.htm#nil"><B>nil</B></A> if there is no <I>result-form</I>. <P>
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<P><B>Description:</B><P>
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<P>
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<A REL=DEFINITION HREF="#dolist"><B>dolist</B></A> iterates over the elements of a <A REL=DEFINITION HREF="26_glo_l.htm#list"><I>list</I></A>. The body of <A REL=DEFINITION HREF="#dolist"><B>dolist</B></A> is like a <A REL=DEFINITION HREF="s_tagbod.htm#tagbody"><B>tagbody</B></A>. It consists of a series of <I>tags</I> and <I>statements</I>. <P>
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<A REL=DEFINITION HREF="#dolist"><B>dolist</B></A> evaluates <I>list-form</I>, which should produce a <A REL=DEFINITION HREF="26_glo_l.htm#list"><I>list</I></A>. It then executes the body once for each element in the <A REL=DEFINITION HREF="26_glo_l.htm#list"><I>list</I></A>, in the order in which the <I>tags</I> and <I>statements</I> occur, with <I>var</I> bound to the element. Then <I>result-form</I> is evaluated. <I>tags</I> label <I>statements</I>. <P>
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At the time <I>result-form</I> is processed, <I>var</I> is bound to <A REL=DEFINITION HREF="a_nil.htm#nil"><B>nil</B></A>. <P>
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An <A REL=DEFINITION HREF="26_glo_i.htm#implicit_block"><I>implicit block</I></A> named <A REL=DEFINITION HREF="a_nil.htm#nil"><B>nil</B></A> surrounds <A REL=DEFINITION HREF="#dolist"><B>dolist</B></A>. <A REL=DEFINITION HREF="m_return.htm#return"><B>return</B></A> may be used to terminate the loop immediately without performing any further iterations, returning zero or more <A REL=DEFINITION HREF="26_glo_v.htm#value"><I>values</I></A>. <P>
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The <A REL=DEFINITION HREF="26_glo_s.htm#scope"><I>scope</I></A> of the binding of <I>var</I> does not include the <I>list-form</I>, but the <I>result-form</I> is included. <P>
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It is <A REL=DEFINITION HREF="26_glo_i.htm#implementation-dependent"><I>implementation-dependent</I></A> whether <A REL=DEFINITION HREF="#dolist"><B>dolist</B></A> <A REL=DEFINITION HREF="26_glo_e.htm#establish"><I>establishes</I></A> a new <A REL=DEFINITION HREF="26_glo_b.htm#binding"><I>binding</I></A> of <I>var</I> on each iteration or whether it <A REL=DEFINITION HREF="26_glo_e.htm#establish"><I>establishes</I></A> a binding for <I>var</I> once at the beginning and then <I>assigns</I> it on any subsequent iterations. <P>
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<P><B>Examples:</B><P>
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<PRE>
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(setq temp-two '()) => NIL
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(dolist (temp-one '(1 2 3 4) temp-two) (push temp-one temp-two)) => (4 3 2 1)
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(setq temp-two 0) => 0
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(dolist (temp-one '(1 2 3 4)) (incf temp-two)) => NIL
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temp-two => 4
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(dolist (x '(a b c d)) (prin1 x) (princ " "))
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>> A B C D
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=> NIL
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</PRE>
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</TT> <P>
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<P><B>Side Effects:</B> None.
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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="m_do_do.htm#do"><B>do</B></A>, <A REL=DEFINITION HREF="m_dotime.htm#dotimes"><B>dotimes</B></A>, <A REL=DEFINITION HREF="s_tagbod.htm#tagbody"><B>tagbody</B></A>, <A REL=CHILD HREF="03_f.htm">Section 3.6 (Traversal Rules and Side Effects)</A> <P>
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<P><B>Notes:</B><P>
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<P>
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<A REL=DEFINITION HREF="s_go.htm#go"><B>go</B></A> may be used within the body of <A REL=DEFINITION HREF="#dolist"><B>dolist</B></A> to transfer control to a statement labeled by a <I>tag</I>. <P>
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<P>
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<P><HR>The following <A REL=META HREF="../Front/X3J13Iss.htm">X3J13 cleanup issues</A>, <I>not part of the specification</I>, apply to this section:<P><UL><LI> <A REL=CHILD HREF="../Issues/iss240.htm">MAPPING-DESTRUCTIVE-INTERACTION:EXPLICITLY-VAGUE</A><LI> <A REL=CHILD HREF="../Issues/iss097.htm">DECLS-AND-DOC</A><P></UL><HR>
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