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62 lines
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<!DOCTYPE HTML PUBLIC "-//W3O//DTD W3 HTML 2.0//EN">
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<!Converted with LaTeX2HTML 0.6.5 (Tue Nov 15 1994) by Nikos Drakos (nikos@cbl.leeds.ac.uk), CBLU, University of Leeds >
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<HEAD>
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<TITLE>26.3.3. Loop Syntax</TITLE>
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<meta name="description" value=" Loop Syntax">
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<meta name="distribution" value="global">
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<P>
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<b>Common Lisp the Language, 2nd Edition</b>
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<BR> <HR><A NAME=tex2html4580 HREF="node242.html"><IMG ALIGN=BOTTOM ALT="next" SRC="icons/next_motif.gif"></A> <A NAME=tex2html4578 HREF="node238.html"><IMG ALIGN=BOTTOM ALT="up" SRC="icons/up_motif.gif"></A> <A NAME=tex2html4574 HREF="node240.html"><IMG ALIGN=BOTTOM ALT="previous" SRC="icons/previous_motif.gif"></A> <A NAME=tex2html4582 HREF="node1.html"><IMG ALIGN=BOTTOM ALT="contents" SRC="icons/contents_motif.gif"></A> <A NAME=tex2html4583 HREF="index.html"><IMG ALIGN=BOTTOM ALT="index" SRC="icons/index_motif.gif"></A> <BR>
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<B> Next:</B> <A NAME=tex2html4581 HREF="node242.html"> User Extensibility</A>
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<B>Up:</B> <A NAME=tex2html4579 HREF="node238.html"> Parsing Loop Clauses</A>
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<B> Previous:</B> <A NAME=tex2html4575 HREF="node240.html"> Kinds of Loop </A>
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<HR> <P>
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<H2><A NAME=SECTION003033000000000000000>26.3.3. Loop Syntax</A></H2>
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<P>
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<img align=bottom alt="change_begin" src="gif/change_begin.gif"><br>
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The following syntax description provides an overview of the syntax
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for loop clauses. Detailed syntax descriptions of individual clauses
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appear in sections <A HREF="node244.html#LOOPITERATIONSECTION">26.6</A> through <A HREF="node250.html#LOOPMISCSECTION">26.12</A>.
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A loop consists of the
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following types of clauses:
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<P>
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<PRE>
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<i>initial-final</i> ::= <i>initially</i> | <i>finally</i>
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<i>variables</i> ::= <i>with</i> | <i>initial-final</i> | <i>for-as</i> | <i>repeat</i>
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<i>main</i> ::= <i>unconditional</i> | <i>accumulation</i> | <i>conditional</i>
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| <i>termination</i> | <i>initial-final</i>
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<i>loop</i> ::= (loop [named <i>name</i>] {<i>variables</i>}* {<i>main</i>}*)
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</PRE>
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<P>
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Note that a loop must have at least one clause; however, for
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backward compatibility, the following format is also supported:
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<P><pre>
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(loop {<i>tag</i> | <i>expr</i>}*)
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</pre><P>
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where <i>expr</i> is any Common Lisp expression that can be evaluated, and
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<i>tag</i> is any symbol not identifiable as a loop keyword. Such a format
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is roughly equivalent to the following one:
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<P>
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<P><pre>
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(loop do {<i>tag</i> | <i>expr</i>}*)
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</pre><P>
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<P>
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A loop prologue consists of any automatic variable initializations prescribed
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by the <i>variable</i> clauses, along with any <i>initially</i> clauses
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in the order they appear in the source.
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<P>
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A loop epilogue consists of <i>finally</i> clauses, if any, along
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with any implicit return value from an <i>accumulation</i> clause or
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an <i>end-test</i> clause.
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<P>
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<br><img align=bottom alt="change_end" src="gif/change_end.gif">
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<HR>
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<P><ADDRESS>
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AI.Repository@cs.cmu.edu
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</ADDRESS>
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