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>remove-duplicates, delete-duplicates | Common Lisp Nova Spec</TITLE
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>Common Lisp Nova Spec</A
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> <SPAN CLASS="breadcrumb-item"
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>→ <A HREF="17_Sequences.html"
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>17. Sequences</A
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> <SPAN CLASS="breadcrumb-item"
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>→ <A HREF="17_3_Sequences_Dictionary.html"
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>17.3 Sequences Dictionary</A
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>→ <A HREF="f_remove-duplicates.html"
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>remove-duplicates, delete-duplicates</A
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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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><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="remove-duplicates, delete-duplicates"
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></SPAN
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><B
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>remove-duplicates, delete-duplicates</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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><TABLE CELLPADDING="0" CELLSPACING="0"
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><TR
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><TD VALIGN="BASELINE" ALIGN="LEFT" NOWRAP="NOWRAP"
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><B
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>remove-duplicates</B
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><SPAN CLASS="cmssi"
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> </SPAN
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><SPAN CLASS="cmssi"
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>sequence</SPAN
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><SPAN CLASS="cmtt"
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> </SPAN
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><SPAN CLASS="cmtt"
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>&key</SPAN
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><SPAN CLASS="cmssi"
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> </SPAN
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></TD
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><TD VALIGN="BASELINE" ALIGN="LEFT"
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><SPAN CLASS="cmssi"
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>from-end</SPAN
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> <SPAN CLASS="cmssi"
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>test</SPAN
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> <SPAN CLASS="cmssi"
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>test-not</SPAN
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><BR
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><SPAN CLASS="cmssi"
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>start</SPAN
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> <SPAN CLASS="cmssi"
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>end</SPAN
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> <SPAN CLASS="cmssi"
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>key</SPAN
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></TD
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></TR
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></TABLE
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><DIV
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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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> <SPAN CLASS="cmssi"
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>result-sequence</SPAN
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></DIV
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><TABLE CELLPADDING="0" CELLSPACING="0"
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><TR
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><TD VALIGN="BASELINE" ALIGN="LEFT" NOWRAP="NOWRAP"
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><B
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>delete-duplicates</B
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><SPAN CLASS="cmssi"
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> </SPAN
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><SPAN CLASS="cmssi"
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>sequence</SPAN
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><SPAN CLASS="cmtt"
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> </SPAN
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><SPAN CLASS="cmtt"
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>&key</SPAN
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><SPAN CLASS="cmssi"
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> </SPAN
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></TD
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><TD VALIGN="BASELINE" ALIGN="LEFT"
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><SPAN CLASS="cmssi"
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>from-end</SPAN
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> <SPAN CLASS="cmssi"
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>test</SPAN
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> <SPAN CLASS="cmssi"
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>test-not</SPAN
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><BR
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><SPAN CLASS="cmssi"
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>start</SPAN
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> <SPAN CLASS="cmssi"
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>end</SPAN
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> <SPAN CLASS="cmssi"
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>key</SPAN
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></TD
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></TR
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></TABLE
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><DIV
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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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> <SPAN CLASS="cmssi"
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>result-sequence</SPAN
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></DIV
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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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>sequence</VAR
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> — a <A HREF="26_1_Glossary.html#proper_sequence"
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><EM CLASS="term"
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>proper sequence</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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>from-end</VAR
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> — a <A HREF="26_1_Glossary.html#generalized_boolean"
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><EM CLASS="term"
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>generalized boolean</EM
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></A
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>. The default is <A HREF="26_1_Glossary.html#false"
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><EM CLASS="term"
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>false</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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>test</VAR
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> — a <A HREF="26_1_Glossary.html#designator"
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><EM CLASS="term"
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>designator</EM
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></A
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> for a <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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> of two <A HREF="26_1_Glossary.html#argument"
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><EM CLASS="term"
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>arguments</EM
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></A
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> that returns a <A HREF="26_1_Glossary.html#generalized_boolean"
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><EM CLASS="term"
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>generalized boolean</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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>test-not</VAR
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> — a <A HREF="26_1_Glossary.html#designator"
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><EM CLASS="term"
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>designator</EM
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></A
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> for a <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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> of two <A HREF="26_1_Glossary.html#argument"
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><EM CLASS="term"
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>arguments</EM
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></A
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> that returns a <A HREF="26_1_Glossary.html#generalized_boolean"
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><EM CLASS="term"
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>generalized boolean</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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>start</VAR
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>, <VAR CLASS="param"
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>end</VAR
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> — <A HREF="26_1_Glossary.html#bounding_index_designator"
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><EM CLASS="term"
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>bounding index designators</EM
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></A
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> of <VAR CLASS="param"
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>sequence</VAR
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>. The defaults for <VAR CLASS="param"
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>start</VAR
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> and <VAR CLASS="param"
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>end</VAR
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> are <CODE CLASS="f"
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>0</CODE
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> and <SPAN CLASS="misc"
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><B
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>nil</B
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></SPAN
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>, respectively. </P
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><P CLASS="j"
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><VAR CLASS="param"
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>key</VAR
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> — a <A HREF="26_1_Glossary.html#designator"
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><EM CLASS="term"
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>designator</EM
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></A
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> for a <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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> of one argument, or <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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><P CLASS="j"
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><VAR CLASS="param"
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>result-sequence</VAR
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> — a <A HREF="26_1_Glossary.html#sequence"
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><EM CLASS="term"
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>sequence</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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><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_remove-duplicates.html" CLASS="funref"
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><B
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>remove-duplicates</B
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></A
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> returns a modified copy of <VAR CLASS="param"
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>sequence</VAR
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> from which any element that matches another element occurring in <VAR CLASS="param"
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>sequence</VAR
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> has been removed. </P
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><P CLASS="j"
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>If <VAR CLASS="param"
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>sequence</VAR
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> is a <A HREF="26_1_Glossary.html#vector"
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><EM CLASS="term"
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>vector</EM
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></A
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>, the result is a <A HREF="26_1_Glossary.html#vector"
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><EM CLASS="term"
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>vector</EM
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></A
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> that has the same <A HREF="26_1_Glossary.html#actual_array_element_type"
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><EM CLASS="term"
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|
>actual array element type</EM
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></A
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|
> as <VAR CLASS="param"
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>sequence</VAR
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>. If <VAR CLASS="param"
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>sequence</VAR
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> is a <A HREF="26_1_Glossary.html#list"
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><EM CLASS="term"
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|
>list</EM
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></A
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>, the result is a <A HREF="26_1_Glossary.html#list"
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><EM CLASS="term"
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>list</EM
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></A
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>. </P
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><P CLASS="j"
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><A HREF="f_remove-duplicates.html" CLASS="funref"
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><B
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>delete-duplicates</B
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></A
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> is like <A HREF="f_remove-duplicates.html" CLASS="funref"
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><B
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>remove-duplicates</B
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></A
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>, but <A HREF="f_remove-duplicates.html" CLASS="funref"
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><B
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>delete-duplicates</B
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></A
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> may modify <VAR CLASS="param"
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>sequence</VAR
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>. </P
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><P CLASS="j"
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>The elements of <VAR CLASS="param"
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>sequence</VAR
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> are compared <A HREF="26_1_Glossary.html#pairwise"
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><EM CLASS="term"
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>pairwise</EM
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></A
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>, and if any two match, then the one occurring earlier in <VAR CLASS="param"
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>sequence</VAR
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> is discarded, unless <VAR CLASS="param"
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>from-end</VAR
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> is <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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>, in which case the one later in <VAR CLASS="param"
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>sequence</VAR
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> is discarded. </P
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><P CLASS="j"
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><A HREF="f_remove-duplicates.html" CLASS="funref"
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><B
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>remove-duplicates</B
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></A
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> and <A HREF="f_remove-duplicates.html" CLASS="funref"
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><B
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>delete-duplicates</B
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></A
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> return a <A HREF="26_1_Glossary.html#sequence"
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><EM CLASS="term"
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>sequence</EM
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></A
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> of the same <A HREF="26_1_Glossary.html#type"
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><EM CLASS="term"
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>type</EM
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></A
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> as <VAR CLASS="param"
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>sequence</VAR
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> with enough elements removed so that no two of the remaining elements match. The order of the elements remaining in the result is the same as the order in which they appear in <VAR CLASS="param"
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>sequence</VAR
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>. </P
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><P CLASS="j"
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><A HREF="f_remove-duplicates.html" CLASS="funref"
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><B
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>remove-duplicates</B
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></A
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> returns a <A HREF="26_1_Glossary.html#sequence"
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><EM CLASS="term"
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>sequence</EM
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></A
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> that may share with <VAR CLASS="param"
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>sequence</VAR
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> or may be <A HREF="26_1_Glossary.html#identical"
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><EM CLASS="term"
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>identical</EM
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></A
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> to <VAR CLASS="param"
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>sequence</VAR
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> if no elements need to be removed. </P
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><P CLASS="j"
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><A HREF="f_remove-duplicates.html" CLASS="funref"
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><B
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>delete-duplicates</B
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></A
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>, when <VAR CLASS="param"
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>sequence</VAR
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> is a <A HREF="26_1_Glossary.html#list"
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><EM CLASS="term"
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>list</EM
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></A
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>, is permitted to <A HREF="f_setf.html" CLASS="macref"
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><B
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>setf</B
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></A
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> any part, <A HREF="f_car.html" CLASS="funref"
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><B
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>car</B
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></A
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> or <A HREF="f_car.html" CLASS="funref"
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><B
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>cdr</B
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></A
|
|
>, of the top-level list structure in that <VAR CLASS="param"
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>sequence</VAR
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>. When <VAR CLASS="param"
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>sequence</VAR
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> is a <A HREF="26_1_Glossary.html#vector"
|
|
><EM CLASS="term"
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>vector</EM
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></A
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>, <A HREF="f_remove-duplicates.html" CLASS="funref"
|
|
><B
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>delete-duplicates</B
|
|
></A
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> is permitted to change the dimensions of the <A HREF="26_1_Glossary.html#vector"
|
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><EM CLASS="term"
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|
>vector</EM
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|
></A
|
|
> and to slide its elements into new positions without permuting them to produce the resulting <A HREF="26_1_Glossary.html#vector"
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><EM CLASS="term"
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>vector</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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><B
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|
>Examples</B
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|
></DT
|
|
><DD
|
|
><PRE CLASS="screen"
|
|
>(remove-duplicates "aBcDAbCd" :test #'char-equal :from-end t) <SPAN CLASS="cmsy"
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><SPAN CLASS="arrow"
|
|
>→</SPAN
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|
></SPAN
|
|
> "aBcD"
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(remove-duplicates '(a b c b d d e)) <SPAN CLASS="cmsy"
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><SPAN CLASS="arrow"
|
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>→</SPAN
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></SPAN
|
|
> (A C B D E)
|
|
(remove-duplicates '(a b c b d d e) :from-end t) <SPAN CLASS="cmsy"
|
|
><SPAN CLASS="arrow"
|
|
>→</SPAN
|
|
></SPAN
|
|
> (A B C D E)
|
|
(remove-duplicates '((foo #\a) (bar #\%) (baz #\A))
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:test #'char-equal :key #'cadr) <SPAN CLASS="cmsy"
|
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><SPAN CLASS="arrow"
|
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>→</SPAN
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|
></SPAN
|
|
> ((BAR #\%) (BAZ #\A))
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(remove-duplicates '((foo #\a) (bar #\%) (baz #\A))
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:test #'char-equal :key #'cadr :from-end t) <SPAN CLASS="cmsy"
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><SPAN CLASS="arrow"
|
|
>→</SPAN
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></SPAN
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|
> ((FOO #\a) (BAR #\%))
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|
(setq tester (list 0 1 2 3 4 5 6))
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(delete-duplicates tester :key #'oddp :start 1 :end 6) <SPAN CLASS="cmsy"
|
|
><SPAN CLASS="arrow"
|
|
>→</SPAN
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></SPAN
|
|
> (0 4 5 6)</PRE
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></DD
|
|
><DT
|
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><B
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|
>Side Effects</B
|
|
></DT
|
|
><DD
|
|
><P CLASS="j"
|
|
><A HREF="f_remove-duplicates.html" CLASS="funref"
|
|
><B
|
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>delete-duplicates</B
|
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></A
|
|
> might destructively modify <VAR CLASS="param"
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|
>sequence</VAR
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|
>.</P
|
|
></DD
|
|
><DT
|
|
><B
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|
>Exceptional Situations</B
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></DT
|
|
><DD
|
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><P CLASS="j"
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|
>Should signal an error of <A HREF="26_1_Glossary.html#type"
|
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><EM CLASS="term"
|
|
>type</EM
|
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></A
|
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> <A HREF="t_type-error.html" CLASS="typeref"
|
|
><B
|
|
>type-error</B
|
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></A
|
|
> if <VAR CLASS="param"
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|
>sequence</VAR
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> is not a <A HREF="26_1_Glossary.html#proper_sequence"
|
|
><EM CLASS="term"
|
|
>proper sequence</EM
|
|
></A
|
|
>.</P
|
|
></DD
|
|
><DT
|
|
><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="3_2_Compilation.html#sec_3_2_1" CLASS="secref"
|
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><SPAN CLASS="cmr"
|
|
>Section</SPAN
|
|
> <SPAN CLASS="cmr"
|
|
>3.2.1</SPAN
|
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> <SPAN CLASS="cmr"
|
|
>(Compiler</SPAN
|
|
> <SPAN CLASS="cmr"
|
|
>Terminology)</SPAN
|
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></A
|
|
>, <A HREF="3_6_Traversal_Rules_and_Side_Effects.html#sec_3_6" CLASS="secref"
|
|
><SPAN CLASS="cmr"
|
|
>Section</SPAN
|
|
> <SPAN CLASS="cmr"
|
|
>3.6</SPAN
|
|
> <SPAN CLASS="cmr"
|
|
>(Traversal</SPAN
|
|
> <SPAN CLASS="cmr"
|
|
>Rules</SPAN
|
|
> <SPAN CLASS="cmr"
|
|
>and</SPAN
|
|
> <SPAN CLASS="cmr"
|
|
>Side</SPAN
|
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> <SPAN CLASS="cmr"
|
|
>Effects)</SPAN
|
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></A
|
|
></P
|
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></DD
|
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><DT
|
|
><B
|
|
>Notes</B
|
|
></DT
|
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><DD
|
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><P CLASS="j"
|
|
>If <VAR CLASS="param"
|
|
>sequence</VAR
|
|
> is a <A HREF="26_1_Glossary.html#vector"
|
|
><EM CLASS="term"
|
|
>vector</EM
|
|
></A
|
|
>, the result might or might not be simple, and might or might not be <A HREF="26_1_Glossary.html#identical"
|
|
><EM CLASS="term"
|
|
>identical</EM
|
|
></A
|
|
> to <VAR CLASS="param"
|
|
>sequence</VAR
|
|
>. </P
|
|
><P CLASS="j"
|
|
>The <SPAN CLASS="kwd"
|
|
><SPAN CLASS="cmtt"
|
|
>:test-not</SPAN
|
|
></SPAN
|
|
> <A HREF="26_1_Glossary.html#argument"
|
|
><EM CLASS="term"
|
|
>argument</EM
|
|
></A
|
|
> is deprecated. </P
|
|
><P CLASS="j"
|
|
>These functions are useful for converting <VAR CLASS="param"
|
|
>sequence</VAR
|
|
> into a canonical form suitable for representing a set.</P
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