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72 lines
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<!DOCTYPE HTML PUBLIC "-//W3O//DTD W3 HTML 2.0//EN">
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<!Converted with LaTeX2HTML 0.6.5 (Tue Nov 15 1994) by Nikos Drakos (nikos@cbl.leeds.ac.uk), CBLU, University of Leeds >
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<HEAD>
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<TITLE>A.3.3. Defining New Series Functions</TITLE>
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</HEAD>
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<BODY>
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<meta name="description" value=" Defining New Series Functions">
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<meta name="keywords" value="clm">
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<meta name="resource-type" value="document">
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<meta name="distribution" value="global">
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<P>
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<b>Common Lisp the Language, 2nd Edition</b>
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<BR> <HR><A NAME=tex2html6190 HREF="node360.html"><IMG ALIGN=BOTTOM ALT="next" SRC="icons/next_motif.gif"></A> <A NAME=tex2html6188 HREF="node356.html"><IMG ALIGN=BOTTOM ALT="up" SRC="icons/up_motif.gif"></A> <A NAME=tex2html6182 HREF="node358.html"><IMG ALIGN=BOTTOM ALT="previous" SRC="icons/previous_motif.gif"></A> <A NAME=tex2html6192 HREF="node1.html"><IMG ALIGN=BOTTOM ALT="contents" SRC="icons/contents_motif.gif"></A> <A NAME=tex2html6193 HREF="index.html"><IMG ALIGN=BOTTOM ALT="index" SRC="icons/index_motif.gif"></A> <BR>
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<B> Next:</B> <A NAME=tex2html6191 HREF="node360.html"> Declarations</A>
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<B>Up:</B> <A NAME=tex2html6189 HREF="node356.html"> Optimization</A>
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<B> Previous:</B> <A NAME=tex2html6183 HREF="node358.html"> Constraint Cycles</A>
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<HR> <P>
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<H2><A NAME=SECTION003433000000000000000>A.3.3. Defining New Series Functions</A></H2>
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<P>
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<img align=bottom alt="change_begin" src="gif/change_begin.gif"><br>
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New functions operating on series can be defined just as easily as new
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functions operating on any other data type. However, expressions
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containing these new functions cannot be transformed into loops unless a
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complete analysis of the functions is available. Among other things,
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this implies that the definition of a new series function must appear
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before its first use.
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<P>
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<BR><b>[Declaration specifier]</b><BR>
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<tt>optimizable-series-function</tt><P>The declaration specifier <tt>(optimizable-series-function <i>integer</i>)</tt> indicates
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that the function being defined is a series function that needs to be
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analyzed so that it can be optimized when it appears in series expressions.
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(A warning is issued if the function being defined neither takes a series
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as input nor produces a series as output.) <i>Integer</i> (default 1)
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specifies the number of values returned by the function being defined.
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(This cannot necessarily be determined by local analysis.) The only place
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<tt>optimizable-series-function</tt> is allowed to appear is in a declaration
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immediately inside a <tt>defun</tt>. As an example, the following shows how a
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simplified version of <tt>collect-sum</tt> could be defined.
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<P><pre>
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(defun simple-collect-sum (numbers)
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(declare (optimizable-series-function 1))
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(collect-fn 'number #'(lambda () 0) #'+ numbers))
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</pre><P>
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<P>
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<BR><b>[Declaration specifier]</b><BR>
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<tt>off-line-port</tt><P>The declaration specifier
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<tt>(off-line-port <i>port-spec1</i> <i>port-spec2</i> ...)</tt> specifies that the
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indicated inputs and outputs are off-line. This declaration
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specifier is only allowed in a <tt>defun</tt> that contains the declaration
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<tt>optimizable-series-function</tt>. Each <i>port-spec</i> must either be a symbol
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that is one of the inputs of the function or an integer <i>j</i> indicating the
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<i>j</i>th output (counting from zero). For example, <tt>(off-line-port x 1)</tt>
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indicates that the input <tt>x</tt> and the second output are off-line.
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Every port that is not mentioned in an <tt>off-line-port</tt>
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declaration is assumed to be on-line. A warning is issued whenever a
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port's actual on-line/off-line status does not agree with its declared
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status. This makes it easier to keep track of which ports are off-line and
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which are not. Note that off-line ports virtually never arise when
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defining scanners or reducers.
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<br><img align=bottom alt="change_end" src="gif/change_end.gif">
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<P>
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<BR> <HR><A NAME=tex2html6190 HREF="node360.html"><IMG ALIGN=BOTTOM ALT="next" SRC="icons/next_motif.gif"></A> <A NAME=tex2html6188 HREF="node356.html"><IMG ALIGN=BOTTOM ALT="up" SRC="icons/up_motif.gif"></A> <A NAME=tex2html6182 HREF="node358.html"><IMG ALIGN=BOTTOM ALT="previous" SRC="icons/previous_motif.gif"></A> <A NAME=tex2html6192 HREF="node1.html"><IMG ALIGN=BOTTOM ALT="contents" SRC="icons/contents_motif.gif"></A> <A NAME=tex2html6193 HREF="index.html"><IMG ALIGN=BOTTOM ALT="index" SRC="icons/index_motif.gif"></A> <BR>
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<B> Next:</B> <A NAME=tex2html6191 HREF="node360.html"> Declarations</A>
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<B>Up:</B> <A NAME=tex2html6189 HREF="node356.html"> Optimization</A>
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<B> Previous:</B> <A NAME=tex2html6183 HREF="node358.html"> Constraint Cycles</A>
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<HR> <P>
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<HR>
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<P><ADDRESS>
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AI.Repository@cs.cmu.edu
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</ADDRESS>
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