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51 lines
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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: Section 9.1.4.2</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="09_adaa.htm"><IMG WIDTH=40 HEIGHT=40 ALT="[Previous]" SRC="../Graphics/Prev.gif" ALIGN=Bottom></A><A REL=UP HREF="09_ad.htm"><IMG WIDTH=40 HEIGHT=40 ALT="[Up]" SRC="../Graphics/Up.gif" ALIGN=Bottom></A><A REL=NEXT HREF="09_adba.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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9.1.4.2 Restarts</H2> <P>
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The interactive condition handler returns only through non-local transfer of control to specially defined <A REL=DEFINITION HREF="26_glo_r.htm#restart"><I>restarts</I></A> that can be set up either by the system or by user code. Transferring control to a restart is called ``invoking'' the restart. Like handlers, active <A REL=DEFINITION HREF="26_glo_r.htm#restart"><I>restarts</I></A> are <I>established</I> dynamically, and only active <A REL=DEFINITION HREF="26_glo_r.htm#restart"><I>restarts</I></A> can be invoked. An active <A REL=DEFINITION HREF="26_glo_r.htm#restart"><I>restart</I></A> can be invoked by the user from the debugger or by a program by using <A REL=DEFINITION HREF="f_invo_1.htm#invoke-restart"><B>invoke-restart</B></A>. <P>
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A <A REL=DEFINITION HREF="26_glo_r.htm#restart"><I>restart</I></A> contains a <A REL=DEFINITION HREF="26_glo_f.htm#function"><I>function</I></A> to be <I>called</I> when the <A REL=DEFINITION HREF="26_glo_r.htm#restart"><I>restart</I></A> is invoked, an optional name that can be used to find or invoke the <A REL=DEFINITION HREF="26_glo_r.htm#restart"><I>restart</I></A>, and an optional set of interaction information for the debugger to use to enable the user to manually invoke a <A REL=DEFINITION HREF="26_glo_r.htm#restart"><I>restart</I></A>. <P>
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The name of a <A REL=DEFINITION HREF="26_glo_r.htm#restart"><I>restart</I></A> is used by <A REL=DEFINITION HREF="f_invo_1.htm#invoke-restart"><B>invoke-restart</B></A>. <A REL=DEFINITION HREF="26_glo_r.htm#restart"><I>Restarts</I></A> that can be invoked only within the debugger do not need names. <P>
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<A REL=DEFINITION HREF="26_glo_r.htm#restart"><I>Restarts</I></A> can be established by using <A REL=DEFINITION HREF="m_rst_bi.htm#restart-bind"><B>restart-bind</B></A>, <A REL=DEFINITION HREF="m_rst_ca.htm#restart-case"><B>restart-case</B></A>, and <A REL=DEFINITION HREF="m_w_smp_.htm#with-simple-restart"><B>with-simple-restart</B></A>. A <A REL=DEFINITION HREF="26_glo_r.htm#restart"><I>restart</I></A> function can itself invoke any other <A REL=DEFINITION HREF="26_glo_r.htm#restart"><I>restart</I></A> that was active at the time of establishment of the <A REL=DEFINITION HREF="26_glo_r.htm#restart"><I>restart</I></A> of which the <A REL=DEFINITION HREF="26_glo_f.htm#function"><I>function</I></A> is part. <P>
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The <A REL=DEFINITION HREF="26_glo_r.htm#restart"><I>restarts</I></A> <I>established</I> by a <A REL=DEFINITION HREF="m_rst_bi.htm#restart-bind"><B>restart-bind</B></A> <A REL=DEFINITION HREF="26_glo_f.htm#form"><I>form</I></A>, a <A REL=DEFINITION HREF="m_rst_ca.htm#restart-case"><B>restart-case</B></A> <A REL=DEFINITION HREF="26_glo_f.htm#form"><I>form</I></A>, or a <A REL=DEFINITION HREF="m_w_smp_.htm#with-simple-restart"><B>with-simple-restart</B></A> <A REL=DEFINITION HREF="26_glo_f.htm#form"><I>form</I></A> have <A REL=DEFINITION HREF="26_glo_d.htm#dynamic_extent"><I>dynamic extent</I></A> which extends for the duration of that <A REL=DEFINITION HREF="26_glo_f.htm#form"><I>form</I></A>'s execution. <P>
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<A REL=DEFINITION HREF="26_glo_r.htm#restart"><I>Restarts</I></A> of the same name can be ordered from least recent to most recent according to the following two rules: <P>
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<P><DL><P>
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<DT>1. Each <A REL=DEFINITION HREF="26_glo_r.htm#restart"><I>restart</I></A> in a set of active restarts R1 is more recent than every <A REL=DEFINITION HREF="26_glo_r.htm#restart"><I>restart</I></A> in a set R2 if the <A REL=DEFINITION HREF="26_glo_r.htm#restart"><I>restarts</I></A> in R2 were active when the <A REL=DEFINITION HREF="26_glo_r.htm#restart"><I>restarts</I></A> in R1 were established. <P><DD>
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<DT>2. Let r1 and r2 be two active <A REL=DEFINITION HREF="26_glo_r.htm#restart"><I>restarts</I></A> with the same name established by the same <A REL=DEFINITION HREF="26_glo_f.htm#form"><I>form</I></A>. Then r1 is more recent than r2 if r1 was defined to the left of r2 in the <A REL=DEFINITION HREF="26_glo_f.htm#form"><I>form</I></A> that established them. <P><DD>
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<P></DL><P>
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If a <A REL=DEFINITION HREF="26_glo_r.htm#restart"><I>restart</I></A> is invoked but does not transfer control, the values resulting from the <A REL=DEFINITION HREF="26_glo_r.htm#restart"><I>restart</I></A> function are returned by the function that invoked the restart, either <A REL=DEFINITION HREF="f_invo_1.htm#invoke-restart"><B>invoke-restart</B></A> or <A REL=DEFINITION HREF="f_invo_2.htm#invoke-restart-interactively"><B>invoke-restart-interactively</B></A>. <P>
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<A REL=CHILD HREF="09_adba.htm"><H2>
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9.1.4.2.1 Interactive Use of Restarts</H2></A><P>
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<A REL=CHILD HREF="09_adbb.htm"><H2>
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9.1.4.2.2 Interfaces to Restarts</H2></A><P>
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<A REL=CHILD HREF="09_adbc.htm"><H2>
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9.1.4.2.3 Restart Tests</H2></A><P>
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<A REL=CHILD HREF="09_adbd.htm"><H2>
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9.1.4.2.4 Associating a Restart with a Condition</H2></A><P><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/iss200.htm">JUN90-TRIVIAL-ISSUES:14</A><LI> <A REL=CHILD HREF="../Issues/iss076.htm">CONDITION-RESTARTS:PERMIT-ASSOCIATION</A><P></UL><HR>
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