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<!DOCTYPE HTML>
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<HTML LANG="en-us"
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>signal | Common Lisp Nova Spec</TITLE
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><A HREF="index.html"
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>Common Lisp Nova Spec</A
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> <SPAN CLASS="breadcrumb-item"
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>→ <A HREF="9_Conditions.html"
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>9. Conditions</A
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> <SPAN CLASS="breadcrumb-item"
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>→ <A HREF="9_2_Conditions_Dictionary.html"
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>9.2 Conditions Dictionary</A
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> <SPAN CLASS="breadcrumb-item"
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>→ <A HREF="f_signal.html"
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>signal</A
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><DIV CLASS="apropos"
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><DIV CLASS="apropos-io"
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><A HREF="f_method-combination-error.html" CLASS="prev"
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>←</A
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><SPAN ID="apropos-label"
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>Apropos </SPAN
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><INPUT ID="apropos" AUTOFOCUS="AUTOFOCUS" PLACEHOLDER="Type here to search" ONINPUT="aproposInput(this);" ONKEYUP="aproposKeyup(event);" ONCHANGE="aproposChange(this);" ONFOCUS="aproposFocus(this);" ONFOCUSOUT="aproposFocusout(this);"
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></DIV
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><DIV CLASS="matter"
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><DIV CLASS="com"
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><DIV CLASS="begincom"
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><HR
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><TABLE WIDTH="100%" CELLSPACING="0" CELLPADDING="0"
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><TR
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><TD ALIGN="LEFT" VALIGN="BASELINE" WIDTH="100%" CLASS="name"
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><SPAN CLASS="idx" DATA-KIND="idxref" DATA-TERM="signal"
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></SPAN
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><B
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>signal</B
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></TD
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><TD ALIGN="RIGHT" VALIGN="BASELINE" WIDTH="0" NOWRAP="NOWRAP" CLASS="ftype"
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><I
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>Function</I
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></TD
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></TR
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></TABLE
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><HR
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></DIV
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><UL CLASS="subtoc"
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></UL
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><DL
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><DT
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><B
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>Syntax</B
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></DT
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><DD
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><P CLASS="j"
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><B
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>signal</B
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> <SPAN CLASS="cmssi"
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>datum</SPAN
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> <SPAN CLASS="cmtt"
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>&rest</SPAN
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> <SPAN CLASS="cmssi"
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>arguments</SPAN
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> <SPAN CLASS="arrow"
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>→</SPAN
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> <SPAN CLASS="misc"
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><B
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>nil</B
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></SPAN
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></P
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></DD
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><DT
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><B
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>Arguments and Values</B
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></DT
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><DD
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><P CLASS="j"
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><VAR CLASS="param"
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>datum</VAR
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>, <VAR CLASS="param"
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>arguments</VAR
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> — <A HREF="26_1_Glossary.html#designator"
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><EM CLASS="term"
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>designators</EM
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></A
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> for a <A HREF="26_1_Glossary.html#condition"
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><EM CLASS="term"
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>condition</EM
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></A
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> of default type <A HREF="t_simple-condition.html" CLASS="typeref"
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><B
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>simple-condition</B
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></A
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>.</P
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></DD
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><DT
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><B
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>Description</B
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></DT
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><DD
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><P CLASS="j"
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><A HREF="26_1_Glossary.html#signal"
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><EM CLASS="term"
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>Signals</EM
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></A
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> the <A HREF="26_1_Glossary.html#condition"
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><EM CLASS="term"
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>condition</EM
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></A
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> denoted by the given <VAR CLASS="param"
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>datum</VAR
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> and <VAR CLASS="param"
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>arguments</VAR
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>. If the <A HREF="26_1_Glossary.html#condition"
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><EM CLASS="term"
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>condition</EM
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></A
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> is not handled, <A HREF="f_signal.html" CLASS="funref"
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><B
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>signal</B
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></A
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> returns <SPAN CLASS="misc"
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><B
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>nil</B
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></SPAN
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>.</P
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></DD
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><DT
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><B
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>Examples</B
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></DT
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><DD
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><PRE CLASS="screen"
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> (defun handle-division-conditions (condition)
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(format t "Considering condition for division condition handling~%")
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(when (and (typep condition 'arithmetic-error)
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(eq '/ (arithmetic-error-operation condition)))
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(invoke-debugger condition)))
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HANDLE-DIVISION-CONDITIONS
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(defun handle-other-arithmetic-errors (condition)
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(format t "Considering condition for arithmetic condition handling~%")
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(when (typep condition 'arithmetic-error)
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(abort)))
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HANDLE-OTHER-ARITHMETIC-ERRORS
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(define-condition a-condition-with-no-handler (condition) ())
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A-CONDITION-WITH-NO-HANDLER
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(signal 'a-condition-with-no-handler)
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NIL
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(handler-bind ((condition #'handle-division-conditions)
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(condition #'handle-other-arithmetic-errors))
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(signal 'a-condition-with-no-handler))
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Considering condition for division condition handling
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Considering condition for arithmetic condition handling
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NIL
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(handler-bind ((arithmetic-error #'handle-division-conditions)
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(arithmetic-error #'handle-other-arithmetic-errors))
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(signal 'arithmetic-error :operation '* :operands '(1.2 b)))
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Considering condition for division condition handling
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Considering condition for arithmetic condition handling
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Back to Lisp Toplevel</PRE
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></DD
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><DT
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><B
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>Side Effects</B
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></DT
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><DD
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><P CLASS="j"
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>The debugger might be entered due to <A HREF="v_break-on-signals.html" CLASS="varref"
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><B
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>*break-on-signals*</B
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></A
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>. </P
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><P CLASS="j"
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>Handlers for the condition being signaled might transfer control.</P
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></DD
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><DT
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><B
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>Affected By</B
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></DT
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><DD
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><P CLASS="j"
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>Existing handler bindings. </P
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><P CLASS="j"
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><A HREF="v_break-on-signals.html" CLASS="varref"
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><B
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>*break-on-signals*</B
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></A
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></P
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></DD
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><DT
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><B
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>See Also</B
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></DT
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><DD
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><P CLASS="j"
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><A HREF="v_break-on-signals.html" CLASS="varref"
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><B
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>*break-on-signals*</B
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></A
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>, <A HREF="f_error.html" CLASS="funref"
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><B
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>error</B
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></A
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>, <A HREF="t_simple-condition.html" CLASS="typeref"
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><B
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>simple-condition</B
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></A
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>, <A HREF="9_1_Condition_System_Concepts.html#sec_9_1_4" CLASS="secref"
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><SPAN CLASS="cmr"
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>Section</SPAN
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> <SPAN CLASS="cmr"
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>9.1.4</SPAN
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> <SPAN CLASS="cmr"
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>(Signaling</SPAN
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> <SPAN CLASS="cmr"
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>and</SPAN
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> <SPAN CLASS="cmr"
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>Handling</SPAN
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> <SPAN CLASS="cmr"
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>Conditions)</SPAN
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></A
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></P
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></DD
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><DT
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><B
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>Notes</B
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></DT
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><DD
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><P CLASS="j"
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>If <CODE CLASS="f"
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>(typep <VAR CLASS="param"
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>datum</VAR
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> *break-on-signals*)</CODE
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> <A HREF="26_1_Glossary.html#yield"
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><EM CLASS="term"
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>yields</EM
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></A
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> <A HREF="26_1_Glossary.html#true"
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><EM CLASS="term"
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>true</EM
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></A
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>, the debugger is entered prior to beginning the signaling process. The <SPAN CLASS="misc"
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><B
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>continue</B
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></SPAN
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> <A HREF="26_1_Glossary.html#restart"
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><EM CLASS="term"
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>restart</EM
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></A
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> can be used to continue with the signaling process. This is also true for all other <A HREF="26_1_Glossary.html#function"
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><EM CLASS="term"
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>functions</EM
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></A
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> and <A HREF="26_1_Glossary.html#macro"
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><EM CLASS="term"
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>macros</EM
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></A
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> that should, might, or must <A HREF="26_1_Glossary.html#signal"
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><EM CLASS="term"
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>signal</EM
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></A
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> <A HREF="26_1_Glossary.html#condition"
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><EM CLASS="term"
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>conditions</EM
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></A
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>.</P
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></DD
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></DL
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></DIV
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></DIV
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><DIV CLASS="footer"
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><DIV CLASS="btmnav"
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>Conversion to HTML copyright 2023 by Gilbert Baumann</DIV
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