331 lines
6.3 KiB
HTML
331 lines
6.3 KiB
HTML
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<!DOCTYPE HTML>
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<HTML LANG="en-us"
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><HEAD
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><TITLE
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>rotatef | Common Lisp Nova Spec</TITLE
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><META CHARSET="US-ASCII"
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><LINK REL="canonical" HREF="f_rotatef.html"
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><LINK REL="next" HREF="t_control-error.html" TYPE="text/html" TITLE="control-error"
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><LINK REL="prev" HREF="f_shiftf.html" TYPE="text/html" TITLE="shiftf"
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><LINK REL="up" HREF="5_3_Data_and_Control_Flow_Dictionary.html" TYPE="text/html" TITLE="5.3 Data and Control Flow Dictionary"
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><LINK REL="start" HREF="index.html" TYPE="text/html" TITLE="Common Lisp Nova Spec"
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><BODY
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><DIV
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><DIV CLASS="topnav"
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><DIV CLASS="breadcrumb"
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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
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> <SPAN CLASS="breadcrumb-item"
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>→ <A HREF="5_Data_and_Control_Flow.html"
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>5. Data and Control Flow</A
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></SPAN
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> <SPAN CLASS="breadcrumb-item"
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>→ <A HREF="5_3_Data_and_Control_Flow_Dictionary.html"
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>5.3 Data and Control Flow Dictionary</A
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></SPAN
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> <SPAN CLASS="breadcrumb-item"
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>→ <A HREF="f_rotatef.html"
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>rotatef</A
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></SPAN
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></DIV
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><DIV CLASS="apropos"
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><DIV CLASS="apropos-io"
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><A HREF="f_shiftf.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="t_control-error.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="rotatef"
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></SPAN
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><B
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>rotatef</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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>Macro</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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>rotatef</B
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> {<VAR CLASS="param"
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>place</VAR
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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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>place</VAR
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> — a <A HREF="26_1_Glossary.html#place"
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><EM CLASS="term"
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>place</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_rotatef.html" CLASS="macref"
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><B
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>rotatef</B
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></A
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> modifies the values of each <VAR CLASS="param"
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>place</VAR
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> by rotating values from one <VAR CLASS="param"
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>place</VAR
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> into another. </P
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><P CLASS="j"
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>If a <VAR CLASS="param"
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>place</VAR
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> produces more values than there are store variables, the extra values are ignored. If a <VAR CLASS="param"
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>place</VAR
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> produces fewer values than there are store variables, the missing values are set to <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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>In the form <CODE CLASS="f"
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>(rotatef <I CLASS="i"
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><I
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>place1</I
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></I
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> <I CLASS="i"
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><I
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>place2</I
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></I
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> ... <I CLASS="i"
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><I
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>placen</I
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></I
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>)</CODE
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>, the values in <I CLASS="i"
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><I
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>place1</I
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></I
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> through <I CLASS="i"
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><I
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>placen</I
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></I
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> are <A HREF="26_1_Glossary.html#read"
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><EM CLASS="term"
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>read</EM
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></A
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> and <EM CLASS="term"
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>written</EM
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>. Values 2 through <I CLASS="i"
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><I
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>n</I
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></I
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> and value 1 are then stored into <I CLASS="i"
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><I
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>place1</I
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></I
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> through <I CLASS="i"
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><I
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>placen</I
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></I
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>. It is as if all the places form an end-around shift register that is rotated one place to the left, with the value of <I CLASS="i"
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><I
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>place1</I
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></I
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> being shifted around the end to <I CLASS="i"
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><I
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>placen</I
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></I
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>. </P
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><P CLASS="j"
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>For information about the <A HREF="26_1_Glossary.html#evaluation"
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><EM CLASS="term"
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>evaluation</EM
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></A
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> of <A HREF="26_1_Glossary.html#subform"
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><EM CLASS="term"
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>subforms</EM
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></A
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> of <VAR CLASS="param"
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>places</VAR
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>, see <A HREF="5_1_Generalized_Reference.html#sec_5_1_1_1" 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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>5.1.1.1</SPAN
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> <SPAN CLASS="cmr"
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>(Evaluation</SPAN
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> <SPAN CLASS="cmr"
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>of</SPAN
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> <SPAN CLASS="cmr"
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>Subforms</SPAN
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> <SPAN CLASS="cmr"
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>to</SPAN
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> <SPAN CLASS="cmr"
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>Places)</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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>Examples</B
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></DT
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><DD
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><PRE CLASS="screen"
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>(let ((n 0)
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(x (list 'a 'b 'c 'd 'e 'f 'g)))
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(rotatef (nth (incf n) x)
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(nth (incf n) x)
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(nth (incf n) x))
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x) <SPAN CLASS="cmsy"
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><SPAN CLASS="arrow"
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>→</SPAN
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></SPAN
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> (A C D B E F G)</PRE
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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_define-setf-expander.html" CLASS="macref"
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><B
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>define-setf-expander</B
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></A
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>, <A HREF="f_defsetf.html" CLASS="macref"
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><B
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>defsetf</B
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></A
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>, <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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>, <A HREF="f_shiftf.html" CLASS="macref"
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><B
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>shiftf</B
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></A
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>, <A HREF="v_macroexpand-hook.html" CLASS="varref"
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><B
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>*macroexpand-hook*</B
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></A
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>, <A HREF="5_1_Generalized_Reference.html#sec_5_1" 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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>5.1</SPAN
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> <SPAN CLASS="cmr"
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>(Generalized</SPAN
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> <SPAN CLASS="cmr"
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>Reference)</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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>The effect of <CODE CLASS="f"
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>(rotatef <VAR CLASS="param"
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>place1</VAR
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> <VAR CLASS="param"
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>place2</VAR
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> ... <VAR CLASS="param"
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>placen</VAR
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>)</CODE
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> is roughly equivalent to</P
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><PRE CLASS="screen"
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>(psetf <VAR CLASS="param"
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>place1</VAR
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> <VAR CLASS="param"
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>place2</VAR
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>
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<VAR CLASS="param"
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>place2</VAR
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> <VAR CLASS="param"
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>place3</VAR
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>
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...
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<VAR CLASS="param"
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>placen</VAR
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> <VAR CLASS="param"
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>place1</VAR
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>)</PRE
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><P CLASS="j"
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>except that the latter would evaluate any <A HREF="26_1_Glossary.html#subform"
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><EM CLASS="term"
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>subforms</EM
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></A
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> of each <CODE CLASS="f"
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>place</CODE
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> twice, whereas <A HREF="f_rotatef.html" CLASS="macref"
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><B
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>rotatef</B
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></A
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> evaluates them once.</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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><A HREF="f_shiftf.html" CLASS="prev"
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>←</A
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><A HREF="t_control-error.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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></DIV
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></DIV
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><SCRIPT
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>domReady();</SCRIPT
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></BODY
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>
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