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>3.7 Destructive Operations | Common Lisp Nova Spec</TITLE
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><DIV CLASS="matter"
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><SECTION
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><H2 ID="sec_3_7" CLASS="HeadII"
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>3.7 Destructive Operations</H2
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><UL CLASS="subtoc"
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><LI
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><A HREF="3_7_Destructive_Operations.html#sec_3_7_1"
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>3.7.1 Modification of Literal Objects</A
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></LI
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><LI
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><A HREF="3_7_Destructive_Operations.html#sec_3_7_2"
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>3.7.2 Transfer of Control during a Destructive Operation</A
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></LI
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><LI
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><A HREF="3_7_Destructive_Operations.html#sec_3_7_2_1"
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>3.7.2.1 Examples of Transfer of Control during a Destructive Operation</A
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></LI
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></UL
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><H3 ID="sec_3_7_1" CLASS="HeadIII"
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>3.7.1 Modification of Literal Objects</H3
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><P CLASS="j"
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>The consequences are undefined if <A HREF="26_1_Glossary.html#literal"
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><EM CLASS="term"
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>literal</EM
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></A
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> <A HREF="26_1_Glossary.html#object"
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><EM CLASS="term"
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>objects</EM
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></A
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> are destructively modified. For this purpose, the following operations are considered <A HREF="26_1_Glossary.html#destructive"
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><EM CLASS="term"
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>destructive</EM
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></A
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>:</P
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><DL
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><DT
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><A HREF="t_random-state.html" CLASS="typeref"
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><B
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>random-state</B
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></A
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></DT
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><DD
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><P CLASS="j"
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>Using it as an <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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> to the <A HREF="26_1_Glossary.html#function"
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><EM CLASS="term"
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>function</EM
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></A
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> <A HREF="f_random.html" CLASS="funref"
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><B
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>random</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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><A HREF="t_cons.html" CLASS="typeref"
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><B
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>cons</B
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></A
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></DT
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><DD
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><P CLASS="j"
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>Changing the <A HREF="26_1_Glossary.html#car"
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><EM CLASS="term"
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>car</EM
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></A
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><SPAN CLASS="meaning"
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><SUB CLASS="sub"
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><SPAN CLASS="cmr"
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>1</SPAN
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></SUB
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></SPAN
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> or <A HREF="26_1_Glossary.html#cdr"
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><EM CLASS="term"
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>cdr</EM
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></A
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><SPAN CLASS="meaning"
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><SUB CLASS="sub"
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><SPAN CLASS="cmr"
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>1</SPAN
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></SUB
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></SPAN
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> of the <A HREF="26_1_Glossary.html#cons"
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><EM CLASS="term"
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>cons</EM
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></A
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>, or performing a <A HREF="26_1_Glossary.html#destructive"
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><EM CLASS="term"
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>destructive</EM
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></A
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> operation on an <A HREF="26_1_Glossary.html#object"
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><EM CLASS="term"
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>object</EM
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></A
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> which is either the <A HREF="26_1_Glossary.html#car"
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><EM CLASS="term"
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>car</EM
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></A
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><SPAN CLASS="meaning"
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><SUB CLASS="sub"
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><SPAN CLASS="cmr"
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>2</SPAN
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></SUB
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></SPAN
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> or the <A HREF="26_1_Glossary.html#cdr"
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><EM CLASS="term"
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>cdr</EM
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></A
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><SPAN CLASS="meaning"
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><SUB CLASS="sub"
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><SPAN CLASS="cmr"
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>2</SPAN
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></SUB
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></SPAN
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> of the <A HREF="26_1_Glossary.html#cons"
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><EM CLASS="term"
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>cons</EM
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></A
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>.</P
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></DD
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><DT
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><A HREF="t_array.html" CLASS="typeref"
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><B
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>array</B
|
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></A
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></DT
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><DD
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><P CLASS="j"
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>Storing a new value into some element of the <A HREF="26_1_Glossary.html#array"
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><EM CLASS="term"
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>array</EM
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></A
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>, or performing a <A HREF="26_1_Glossary.html#destructive"
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><EM CLASS="term"
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>destructive</EM
|
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></A
|
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> operation on an <A HREF="26_1_Glossary.html#object"
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><EM CLASS="term"
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>object</EM
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></A
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> that is already such an <A HREF="26_1_Glossary.html#element"
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><EM CLASS="term"
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>element</EM
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></A
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>. </P
|
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><P CLASS="j"
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>Changing the <A HREF="26_1_Glossary.html#fill_pointer"
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><EM CLASS="term"
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>fill pointer</EM
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></A
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>, <A HREF="26_1_Glossary.html#dimension"
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><EM CLASS="term"
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>dimensions</EM
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></A
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>, or displacement of the <A HREF="26_1_Glossary.html#array"
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><EM CLASS="term"
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>array</EM
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></A
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> (regardless of whether the <A HREF="26_1_Glossary.html#array"
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><EM CLASS="term"
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>array</EM
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></A
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> is <A HREF="26_1_Glossary.html#actually_adjustable"
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><EM CLASS="term"
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>actually adjustable</EM
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></A
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>). </P
|
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><P CLASS="j"
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>Performing a <A HREF="26_1_Glossary.html#destructive"
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><EM CLASS="term"
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>destructive</EM
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></A
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> operation on another <A HREF="26_1_Glossary.html#array"
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><EM CLASS="term"
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>array</EM
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></A
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> that is displaced to the <A HREF="26_1_Glossary.html#array"
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><EM CLASS="term"
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>array</EM
|
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></A
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> or that otherwise shares its contents with the <A HREF="26_1_Glossary.html#array"
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><EM CLASS="term"
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>array</EM
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></A
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>.</P
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></DD
|
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><DT
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><A HREF="t_hash-table.html" CLASS="typeref"
|
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><B
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>hash-table</B
|
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></A
|
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></DT
|
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><DD
|
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><P CLASS="j"
|
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>Performing a <A HREF="26_1_Glossary.html#destructive"
|
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><EM CLASS="term"
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>destructive</EM
|
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></A
|
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> operation on any <A HREF="26_1_Glossary.html#key"
|
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><EM CLASS="term"
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>key</EM
|
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></A
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>. </P
|
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><P CLASS="j"
|
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>Storing a new <A HREF="26_1_Glossary.html#value"
|
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><EM CLASS="term"
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>value</EM
|
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></A
|
|
><SPAN CLASS="meaning"
|
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><SUB CLASS="sub"
|
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><SPAN CLASS="cmr"
|
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>4</SPAN
|
|
></SUB
|
|
></SPAN
|
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> for any <A HREF="26_1_Glossary.html#key"
|
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><EM CLASS="term"
|
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>key</EM
|
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></A
|
|
>, or performing a <A HREF="26_1_Glossary.html#destructive"
|
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><EM CLASS="term"
|
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>destructive</EM
|
|
></A
|
|
> operation on any <A HREF="26_1_Glossary.html#object"
|
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><EM CLASS="term"
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>object</EM
|
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></A
|
|
> that is such a <A HREF="26_1_Glossary.html#value"
|
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><EM CLASS="term"
|
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>value</EM
|
|
></A
|
|
>. </P
|
|
><P CLASS="j"
|
|
>Adding or removing entries from the <A HREF="26_1_Glossary.html#hash_table"
|
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><EM CLASS="term"
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>hash table</EM
|
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></A
|
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>.</P
|
|
></DD
|
|
><DT
|
|
><A HREF="t_structure-object.html" CLASS="typeref"
|
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><B
|
|
>structure-object</B
|
|
></A
|
|
></DT
|
|
><DD
|
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><P CLASS="j"
|
|
>Storing a new value into any slot, or performing a <A HREF="26_1_Glossary.html#destructive"
|
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><EM CLASS="term"
|
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>destructive</EM
|
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></A
|
|
> operation on an <A HREF="26_1_Glossary.html#object"
|
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><EM CLASS="term"
|
|
>object</EM
|
|
></A
|
|
> that is the value of some slot.</P
|
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></DD
|
|
><DT
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><A HREF="t_standard-object.html" CLASS="typeref"
|
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><B
|
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>standard-object</B
|
|
></A
|
|
></DT
|
|
><DD
|
|
><P CLASS="j"
|
|
>Storing a new value into any slot, or performing a <A HREF="26_1_Glossary.html#destructive"
|
|
><EM CLASS="term"
|
|
>destructive</EM
|
|
></A
|
|
> operation on an <A HREF="26_1_Glossary.html#object"
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><EM CLASS="term"
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>object</EM
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></A
|
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> that is the value of some slot. </P
|
|
><P CLASS="j"
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|
>Changing the class of the <A HREF="26_1_Glossary.html#object"
|
|
><EM CLASS="term"
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|
>object</EM
|
|
></A
|
|
> (<I CLASS="i"
|
|
><I
|
|
>e.g.</I
|
|
></I
|
|
>, using the <A HREF="26_1_Glossary.html#function"
|
|
><EM CLASS="term"
|
|
>function</EM
|
|
></A
|
|
> <A HREF="f_change-class.html" CLASS="funref"
|
|
><B
|
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>change-class</B
|
|
></A
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>).</P
|
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></DD
|
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><DT
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><A HREF="t_readtable.html" CLASS="typeref"
|
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><B
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>readtable</B
|
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></A
|
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></DT
|
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><DD
|
|
><P CLASS="j"
|
|
>Altering the <A HREF="26_1_Glossary.html#readtable_case"
|
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><EM CLASS="term"
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>readtable case</EM
|
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></A
|
|
>. </P
|
|
><P CLASS="j"
|
|
>Altering the syntax type of any character in this readtable. </P
|
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><P CLASS="j"
|
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>Altering the <A HREF="26_1_Glossary.html#reader_macro_function"
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><EM CLASS="term"
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>reader macro function</EM
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></A
|
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> associated with any <A HREF="26_1_Glossary.html#character"
|
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><EM CLASS="term"
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>character</EM
|
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></A
|
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> in the <A HREF="26_1_Glossary.html#readtable"
|
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><EM CLASS="term"
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>readtable</EM
|
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></A
|
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>, or altering the <A HREF="26_1_Glossary.html#reader_macro_function"
|
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><EM CLASS="term"
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>reader macro functions</EM
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></A
|
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> associated with <A HREF="26_1_Glossary.html#character"
|
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><EM CLASS="term"
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>characters</EM
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></A
|
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> defined as <A HREF="26_1_Glossary.html#dispatching_macro_character"
|
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><EM CLASS="term"
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>dispatching macro characters</EM
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></A
|
|
> in the <A HREF="26_1_Glossary.html#readtable"
|
|
><EM CLASS="term"
|
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>readtable</EM
|
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></A
|
|
>.</P
|
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></DD
|
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><DT
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><A HREF="t_stream.html" CLASS="typeref"
|
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><B
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>stream</B
|
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></A
|
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></DT
|
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><DD
|
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><P CLASS="j"
|
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>Performing I/O operations on the <A HREF="26_1_Glossary.html#stream"
|
|
><EM CLASS="term"
|
|
>stream</EM
|
|
></A
|
|
>, or <A HREF="26_1_Glossary.html#close"
|
|
><EM CLASS="term"
|
|
>closing</EM
|
|
></A
|
|
> the <A HREF="26_1_Glossary.html#stream"
|
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><EM CLASS="term"
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>stream</EM
|
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></A
|
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>.</P
|
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></DD
|
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><DT
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><SPAN CLASS="cmr"
|
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>All</SPAN
|
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> <SPAN CLASS="cmr"
|
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>other</SPAN
|
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> <SPAN CLASS="cmr"
|
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>standardized</SPAN
|
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> <SPAN CLASS="cmr"
|
|
>types</SPAN
|
|
></DT
|
|
><DD
|
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><P CLASS="j"
|
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>[This category includes, for example, <A HREF="t_character.html" CLASS="typeref"
|
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><B
|
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>character</B
|
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></A
|
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>, <A HREF="t_condition.html" CLASS="typeref"
|
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><B
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>condition</B
|
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></A
|
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>, <A HREF="t_function.html" CLASS="typeref"
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><B
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>function</B
|
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></A
|
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>, <A HREF="t_method-combination.html" CLASS="typeref"
|
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><B
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>method-combination</B
|
|
></A
|
|
>, <A HREF="t_method.html" CLASS="typeref"
|
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><B
|
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>method</B
|
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></A
|
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>, <A HREF="t_number.html" CLASS="typeref"
|
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><B
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>number</B
|
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></A
|
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>, <A HREF="t_package.html" CLASS="typeref"
|
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><B
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>package</B
|
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></A
|
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>, <A HREF="t_pathname.html" CLASS="typeref"
|
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><B
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>pathname</B
|
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></A
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>, <A HREF="t_restart.html" CLASS="typeref"
|
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><B
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>restart</B
|
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></A
|
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>, and <A HREF="t_symbol.html" CLASS="typeref"
|
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><B
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>symbol</B
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></A
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>.] </P
|
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><P CLASS="j"
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>There are no <A HREF="26_1_Glossary.html#standardized"
|
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><EM CLASS="term"
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>standardized</EM
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></A
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> <A HREF="26_1_Glossary.html#destructive"
|
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><EM CLASS="term"
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>destructive</EM
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></A
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|
> operations defined on <A HREF="26_1_Glossary.html#object"
|
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><EM CLASS="term"
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>objects</EM
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></A
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> of these <A HREF="26_1_Glossary.html#type"
|
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><EM CLASS="term"
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>types</EM
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></A
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>.</P
|
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></DD
|
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></DL
|
|
><H3 ID="sec_3_7_2" CLASS="HeadIII"
|
|
>3.7.2 Transfer of Control during a Destructive Operation</H3
|
|
><P CLASS="j"
|
|
>Should a transfer of control out of a <A HREF="26_1_Glossary.html#destructive"
|
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><EM CLASS="term"
|
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>destructive</EM
|
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></A
|
|
> operation occur (<I CLASS="i"
|
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><I
|
|
>e.g.</I
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></I
|
|
>, due to an error) the state of the <VAR CLASS="param"
|
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>object</VAR
|
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> being modified is <A HREF="26_1_Glossary.html#implementation-dependent"
|
|
><EM CLASS="term"
|
|
>implementation-dependent</EM
|
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></A
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>.</P
|
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><H4 ID="sec_3_7_2_1" CLASS="HeadIV"
|
|
>3.7.2.1 Examples of Transfer of Control during a Destructive Operation</H4
|
|
><P CLASS="j"
|
|
>The following examples illustrate some of the many ways in which the <A HREF="26_1_Glossary.html#implementation-dependent"
|
|
><EM CLASS="term"
|
|
>implementation-dependent</EM
|
|
></A
|
|
> nature of the modification can manifest itself.</P
|
|
><PRE CLASS="screen"
|
|
> (let ((a (list 2 1 4 3 7 6 'five)))
|
|
(ignore-errors (sort a #'<))
|
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a)
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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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> (1 2 3 4 6 7 FIVE)
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<SPAN CLASS="sp"
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><SPAN CLASS="arrow withabove"
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><SPAN CLASS="above"
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>or </SPAN
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>→</SPAN
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></SPAN
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> (2 1 4 3 7 6 FIVE)
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<SPAN CLASS="sp"
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><SPAN CLASS="arrow withabove"
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><SPAN CLASS="above"
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>or </SPAN
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>→</SPAN
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></SPAN
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> (2)
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(prog foo ((a (list 1 2 3 4 5 6 7 8 9 10)))
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(sort a #'(lambda (x y) (if (zerop (random 5)) (return-from foo a) (> x y)))))
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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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> (1 2 3 4 5 6 7 8 9 10)
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<SPAN CLASS="sp"
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><SPAN CLASS="arrow withabove"
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><SPAN CLASS="above"
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>or </SPAN
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>→</SPAN
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></SPAN
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> (3 4 5 6 2 7 8 9 10 1)
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<SPAN CLASS="sp"
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><SPAN CLASS="arrow withabove"
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><SPAN CLASS="above"
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>or </SPAN
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>→</SPAN
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></SPAN
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> (1 2 4 3)</PRE
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