345 lines
7.2 KiB
HTML
345 lines
7.2 KiB
HTML
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<!DOCTYPE HTML>
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<HTML LANG="en-us"
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>break | Common Lisp Nova Spec</TITLE
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><SPAN CLASS="breadcrumb-item"
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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_break.html"
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>break</A
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><DIV CLASS="apropos-io"
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><A HREF="f_invoke-debugger.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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><A HREF="v_debugger-hook.html" CLASS="next"
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>→</A
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></DIV
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><DIV ID="apropos-res"
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></DIV
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></DIV
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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="break"
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></SPAN
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><B
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>break</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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>break</B
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> <SPAN CLASS="cmtt"
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>&optional</SPAN
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> <SPAN CLASS="cmssi"
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>format-control</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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>format-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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>format-control</VAR
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> — a <A HREF="26_1_Glossary.html#format_control"
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><EM CLASS="term"
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>format control</EM
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></A
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>. The default is <A HREF="26_1_Glossary.html#implementation-dependent"
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><EM CLASS="term"
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>implementation-dependent</EM
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></A
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>. </P
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><P CLASS="j"
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><VAR CLASS="param"
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>format-arguments</VAR
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> — <A HREF="26_1_Glossary.html#format_argument"
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><EM CLASS="term"
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>format arguments</EM
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></A
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> for the <VAR CLASS="param"
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>format-control</VAR
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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="f_break.html" CLASS="funref"
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><B
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>break</B
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></A
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> <A HREF="26_1_Glossary.html#format"
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><EM CLASS="term"
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>formats</EM
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></A
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> <VAR CLASS="param"
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>format-control</VAR
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> and <VAR CLASS="param"
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>format-arguments</VAR
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> and then goes directly into the debugger without allowing any possibility of interception by programmed error-handling facilities. </P
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><P CLASS="j"
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>If 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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> is used while in the debugger, <A HREF="f_break.html" CLASS="funref"
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><B
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>break</B
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></A
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> immediately returns <SPAN CLASS="misc"
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><B
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>nil</B
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></SPAN
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> without taking any unusual recovery action. </P
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><P CLASS="j"
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><A HREF="f_break.html" CLASS="funref"
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><B
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>break</B
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></A
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> binds <A HREF="v_debugger-hook.html" CLASS="varref"
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><B
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>*debugger-hook*</B
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></A
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> to <SPAN CLASS="misc"
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><B
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>nil</B
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></SPAN
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> before attempting to enter the debugger.</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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> (break "You got here with arguments: ~:S." '(FOO 37 A))
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<SPAN CLASS="cmr"
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>⊳</SPAN
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> BREAK: You got here with these arguments: FOO, 37, A.
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<SPAN CLASS="cmr"
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>⊳</SPAN
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> To continue, type :CONTINUE followed by an option number:
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<SPAN CLASS="cmr"
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>⊳</SPAN
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> 1: Return from BREAK.
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<SPAN CLASS="cmr"
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>⊳</SPAN
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> 2: Top level.
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<SPAN CLASS="cmr"
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>⊳</SPAN
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> Debug> :CONTINUE 1
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<SPAN CLASS="cmr"
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>⊳</SPAN
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> Return from BREAK.
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<SPAN CLASS="cmsy"
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><SPAN CLASS="arrow"
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>→</SPAN
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></SPAN
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> NIL</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 is entered.</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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><A HREF="v_debug-io.html" CLASS="varref"
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><B
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>*debug-io*</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="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="f_invoke-debugger.html" CLASS="funref"
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><B
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>invoke-debugger</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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>Notes</B
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></DT
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><DD
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><P CLASS="j"
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><A HREF="f_break.html" CLASS="funref"
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><B
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>break</B
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></A
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> is used as a way of inserting temporary debugging “breakpoints” in a program, not as a way of signaling errors. For this reason, <A HREF="f_break.html" CLASS="funref"
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><B
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>break</B
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></A
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> does not take the <VAR CLASS="param"
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>continue-format-control</VAR
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> <A HREF="26_1_Glossary.html#argument"
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><EM CLASS="term"
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>argument</EM
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></A
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> that <A HREF="f_cerror.html" CLASS="funref"
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><B
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>cerror</B
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></A
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> takes. This and the lack of any possibility of interception by <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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> <A HREF="26_1_Glossary.html#handle"
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><EM CLASS="term"
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>handling</EM
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></A
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> are the only program-visible differences between <A HREF="f_break.html" CLASS="funref"
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><B
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>break</B
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></A
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> and <A HREF="f_cerror.html" CLASS="funref"
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><B
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>cerror</B
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></A
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>. </P
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><P CLASS="j"
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>The user interface aspects of <A HREF="f_break.html" CLASS="funref"
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><B
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>break</B
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></A
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> and <A HREF="f_cerror.html" CLASS="funref"
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><B
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>cerror</B
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></A
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> are permitted to vary more widely, in order to accomodate the interface needs of the <A HREF="26_1_Glossary.html#implementation"
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><EM CLASS="term"
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>implementation</EM
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></A
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>. For example, it is permissible for a <A HREF="26_1_Glossary.html#Lisp_read-eval-print_loop"
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><EM CLASS="term"
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>Lisp read-eval-print loop</EM
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></A
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> to be entered by <A HREF="f_break.html" CLASS="funref"
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><B
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>break</B
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></A
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> rather than the conventional debugger. </P
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><P CLASS="j"
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><A HREF="f_break.html" CLASS="funref"
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><B
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>break</B
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></A
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> could be defined by:</P
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><PRE CLASS="screen"
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>(defun break (&optional (format-control "Break") &rest format-arguments)
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(with-simple-restart (continue "Return from BREAK.")
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(let ((*debugger-hook* nil))
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(invoke-debugger
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(make-condition 'simple-condition
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:format-control format-control
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:format-arguments format-arguments))))
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nil)</PRE
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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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><A HREF="f_invoke-debugger.html" CLASS="prev"
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>←</A
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><A HREF="v_debugger-hook.html" CLASS="next"
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>→</A
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></DIV
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><DIV CLASS="trail"
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>Conversion to HTML copyright 2023 by Gilbert Baumann</DIV
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>
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