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32 lines
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<TITLE>CLHS: Section 6.1.7.2</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="06_agaa.htm"><IMG WIDTH=40 HEIGHT=40 ALT="[Previous]" SRC="../Graphics/Prev.gif" ALIGN=Bottom></A><A REL=UP HREF="06_ag.htm"><IMG WIDTH=40 HEIGHT=40 ALT="[Up]" SRC="../Graphics/Up.gif" ALIGN=Bottom></A><A REL=NEXT HREF="06_ah.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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6.1.7.2 Initial and Final Execution</H2> <P>
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The <TT>initially</TT> and <TT>finally</TT> constructs evaluate forms that occur before and after the loop body. <P>
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The <TT>initially</TT> construct causes the supplied <I>compound-forms</I> to be evaluated in the loop prologue, which precedes all loop code except for initial settings supplied by constructs <TT>with</TT>, <TT>for</TT>, or <TT>as</TT>. The code for any <TT>initially</TT> clauses is executed in the order in which the clauses appeared in the <A REL=DEFINITION HREF="m_loop.htm#loop"><B>loop</B></A>. <P>
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The <TT>finally</TT> construct causes the supplied <I>compound-forms</I> to be evaluated in the loop epilogue after normal iteration terminates. The code for any <TT>finally</TT> clauses is executed in the order in which the clauses appeared in the <A REL=DEFINITION HREF="m_loop.htm#loop"><B>loop</B></A>. The collected code is executed once in the loop epilogue before any implicit values are returned from the accumulation clauses. An explicit transfer of control (e.g., by <A REL=DEFINITION HREF="m_return.htm#return"><B>return</B></A>, <A REL=DEFINITION HREF="s_go.htm#go"><B>go</B></A>, or <A REL=DEFINITION HREF="s_throw.htm#throw"><B>throw</B></A>) from the loop body, however, will exit the <A REL=DEFINITION HREF="m_loop.htm#loop"><B>loop</B></A> without executing the epilogue code. <P>
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Clauses such as <TT>return</TT>, <TT>always</TT>, <TT>never</TT>, and <TT>thereis</TT> can bypass the <TT>finally</TT> clause. <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>, if the <TT>named</TT> option was supplied) can be used after <TT>finally</TT> to return values from a <A REL=DEFINITION HREF="m_loop.htm#loop"><B>loop</B></A>. Such an <A REL=DEFINITION HREF="26_glo_e.htm#explicit_return"><I>explicit return</I></A> inside the <TT>finally</TT> clause takes precedence over returning the accumulation from clauses supplied by such keywords as <TT>collect</TT>, <TT>nconc</TT>, <TT>append</TT>, <TT>sum</TT>, <TT>count</TT>, <TT>maximize</TT>, and <TT>minimize</TT>; the accumulation values for these preempted clauses are not returned by <A REL=DEFINITION HREF="m_loop.htm#loop"><B>loop</B></A> if <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> is used. <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/iss224.htm">LOOP-NAMED-BLOCK-NIL:OVERRIDE</A><P></UL><HR>
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<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>
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<A REL=COPYRIGHT HREF="../Front/Help.htm#Legal"><I>Copyright 1996-2005, LispWorks Ltd. All rights reserved.</I></A><P>
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