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41 lines
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<TITLE>CLHS: Section 9.1.4.1</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_ad.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_adaa.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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9.1.4.1 Signaling</H2> <P>
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When a <A REL=DEFINITION HREF="26_glo_c.htm#condition"><I>condition</I></A> is signaled, the most recent applicable <A REL=DEFINITION HREF="26_glo_a.htm#active"><I>active</I></A> <A REL=DEFINITION HREF="26_glo_h.htm#handler"><I>handler</I></A> is invoked. Sometimes a handler will decline by simply returning without a transfer of control. In such cases, the next most recent applicable active handler is invoked. <P>
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If there are no applicable handlers for a <A REL=DEFINITION HREF="26_glo_c.htm#condition"><I>condition</I></A> that has been signaled, or if all applicable handlers decline, the <A REL=DEFINITION HREF="26_glo_c.htm#condition"><I>condition</I></A> is unhandled. <P>
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The functions <A REL=DEFINITION HREF="f_cerror.htm#cerror"><B>cerror</B></A> and <A REL=DEFINITION HREF="f_error.htm#error"><B>error</B></A> invoke the interactive <A REL=DEFINITION HREF="26_glo_c.htm#condition"><I>condition</I></A> handler (the debugger) rather than return if the <A REL=DEFINITION HREF="26_glo_c.htm#condition"><I>condition</I></A> being signaled, regardless of its <A REL=DEFINITION HREF="26_glo_t.htm#type"><I>type</I></A>, is unhandled. In contrast, <A REL=DEFINITION HREF="f_signal.htm#signal"><B>signal</B></A> returns <A REL=DEFINITION HREF="a_nil.htm#nil"><B>nil</B></A> if the <A REL=DEFINITION HREF="26_glo_c.htm#condition"><I>condition</I></A> being signaled, regardless of its <A REL=DEFINITION HREF="26_glo_t.htm#type"><I>type</I></A>, is unhandled. <P>
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The <A REL=DEFINITION HREF="26_glo_v.htm#variable"><I>variable</I></A> <A REL=DEFINITION HREF="v_break_.htm#STbreak-on-signalsST"><B>*break-on-signals*</B></A> can be used to cause the debugger to be entered before the signaling process begins. <P>
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The next figure shows <A REL=DEFINITION HREF="26_glo_d.htm#defined_name"><I>defined names</I></A> relating to the <I>signaling</I> of <A REL=DEFINITION HREF="26_glo_c.htm#condition"><I>conditions</I></A>. <P>
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<PRE>
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<A REL=DEFINITION HREF="v_break_.htm#STbreak-on-signalsST">*break-on-signals*</A> <A REL=DEFINITION HREF="a_error.htm#error">error</A> <A REL=DEFINITION HREF="f_warn.htm#warn">warn</A>
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<A REL=DEFINITION HREF="f_cerror.htm#cerror">cerror</A> <A REL=DEFINITION HREF="f_signal.htm#signal">signal</A>
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</PRE>
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<P><B>Figure 9-5. Defined names relating to signaling conditions.</B> <P>
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<A REL=CHILD HREF="09_adaa.htm"><H2>
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9.1.4.1.1 Resignaling a Condition</H2></A><P><HR>
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