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75 lines
4.5 KiB
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
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<TITLE>for - m4 FOR Macro</TITLE>
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<LINK HREF="../pool.css" REL="stylesheet" TYPE="text/css">
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<IMG SRC="../../../../c++boost.gif" WIDTH=276 HEIGHT=86 ALT="C++ Boost">
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<H1 ALIGN=CENTER>for - m4 FOR Macro</H1>
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<P>
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<H2>Introduction</H2>
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<P>
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detail/for.m4 provides <SPAN CLASS="code">BOOST_M4_FOR</SPAN>, an <STRONG>m4</STRONG> macro that provides the equivalent of a <SPAN CLASS="code">#for</SPAN> preprocessor instruction.
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<P>
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<H2>Usage</H2>
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<P>
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This macro must be used by an <STRONG>m4</STRONG> file. This file assumes that the option <SPAN CLASS="code">-P</SPAN> is used, to force an <SPAN CLASS="code">m4_</SPAN> prefix on all builtin symbols.
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<P>
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<H2>Arguments</H2>
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<OL>
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<LI>The name of a variable to hold the current value.</LI>
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<LI>The starting value of the variable.</LI>
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<LI>The ending value of the variable.</LI>
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<LI>The text to repeat. This text may contain references to the variable, which will be replaced with the variable's current value.</LI>
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<LI>The delimeter text (optional).</LI>
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</OL>
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<P>
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If called with the wrong number of arguments (less than 4 or more than 5), <SPAN CLASS="code">BOOST_M4_FOR</SPAN> will exit with an error. If the starting value (<SPAN CLASS="code">$2</SPAN>) is greater than or equal to the ending value (<SPAN CLASS="code">$3</SPAN>), <SPAN CLASS="code">BOOST_M4_FOR</SPAN> will do nothing. Otherwise, it will repeat the text (<SPAN CLASS="code">$4</SPAN>), binding the variable (<SPAN CLASS="code">$1</SPAN>) to the values in the range [starting value (<SPAN CLASS="code">$2</SPAN>), ending value (<SPAN CLASS="code">$3</SPAN>)), and repeat the delimeter text (<SPAN CLASS="code">$5</SPAN>) in-between each occurrence of the repeat text (<SPAN CLASS="code">$4</SPAN>).
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<P>
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<H2>Examples</H2>
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<P>
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Note of the quotation marks (<SPAN CLASS="m4">"</SPAN>) used in the table below are in the input or output; they are shown to delimit whitespace. All code within a pair of quotation marks is intended to be on one line.
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<P>
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<TABLE BORDER ALIGN="center">
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<TR><TH>Input<TH>Output</TR>
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<TR><TD CLASS="m4">"BOOST_M4_FOR(i, 1, 3)"<TD>Boost m4 script: BOOST_M4_FOR: Wrong number of arguments (3)</TR>
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<TR><TD CLASS="m4">"BOOST_M4_FOR(i, 1, 3, i, ` ', 13)"<TD>Boost m4 script: BOOST_M4_FOR: Wrong number of arguments (6)</TR>
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<TR><TD CLASS="m4">"BOOST_M4_FOR(i, 7, 0, i )"<TD>(nothing)</TR>
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<TR><TD CLASS="m4">"BOOST_M4_FOR(i, 0, 0, i )"<TD>(nothing)</TR>
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<TR><TD CLASS="m4">"BOOST_M4_FOR(i, 0, 7, i )"<TD CLASS="m4">"0 1 2 3 4 5 6 "</TR>
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<TR><TD CLASS="m4">"BOOST_M4_FOR(i, -13, -10, i )"<TD CLASS="m4">"-13 -12 -11 "</TR>
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<TR><TD CLASS="m4">"BOOST_M4_FOR(i, 0, 8, BOOST_M4_FOR(j, 0, 4, (i, j) )"<BR>")"<TD CLASS="m4">"(0, 0) (0, 1) (0, 2) (0, 3) "<BR>"(1, 0) (1, 1) (1, 2) (1, 3) "<BR>"(2, 0) (2, 1) (2, 2) (2, 3) "<BR>"(3, 0) (3, 1) (3, 2) (3, 3) "<BR>"(4, 0) (4, 1) (4, 2) (4, 3) "<BR>"(5, 0) (5, 1) (5, 2) (5, 3) "<BR>"(6, 0) (6, 1) (6, 2) (6, 3) "<BR>"(7, 0) (7, 1) (7, 2) (7, 3) "<BR>""</TR>
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<TR><TD CLASS="m4">"BOOST_M4_FOR(i, 7, 0, i, |)"<TD>(nothing)</TR>
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<TR><TD CLASS="m4">"BOOST_M4_FOR(i, 0, 0, i, |)"<TD>(nothing)</TR>
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<TR><TD CLASS="m4">"BOOST_M4_FOR(i, 0, 7, i, |)"<TD CLASS="m4">"0|1|2|3|4|5|6"</TR>
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<TR><TD CLASS="m4">"BOOST_M4_FOR(i, -13, -10, i, `, ')"<TD CLASS="m4">"-13, -12, -11"</TR>
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<TR><TD CLASS="m4">"BOOST_M4_FOR(i, 0, 8, `[BOOST_M4_FOR(j, 0, 4, (i, j), `, ')]', `,"<BR>"')"<TD CLASS="m4">"[(0, 0), (0, 1), (0, 2), (0, 3)],"<BR>"[(1, 0), (1, 1), (1, 2), (1, 3)],"<BR>"[(2, 0), (2, 1), (2, 2), (2, 3)],"<BR>"[(3, 0), (3, 1), (3, 2), (3, 3)],"<BR>"[(4, 0), (4, 1), (4, 2), (4, 3)],"<BR>"[(5, 0), (5, 1), (5, 2), (5, 3)],"<BR>"[(6, 0), (6, 1), (6, 2), (6, 3)],"<BR>"[(7, 0), (7, 1), (7, 2), (7, 3)]"</TR>
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</TABLE>
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<HR>
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<P>
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Copyright © 2000, 2001 Stephen Cleary (<A HREF="mailto:shammah@voyager.net">shammah@voyager.net</A>)
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This file can be redistributed and/or modified under the terms found in <A HREF="../copyright.html">copyright.html</A>
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This software and its documentation is provided "as is" without express or implied warranty, and with no claim as to its suitability for any purpose.
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