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FUNNELWEB MANUAL WEB PAGE
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=========================
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Copyright (c) Ross N. Williams 1992,1999. All rights reserved.
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Permission is granted to redistribute and use this manual in
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any medium, with or without modification, provided that all
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notices (including, without limitation, the copyright
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notice, this permission notice, any record of modification,
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and all legal notices) are preserved on all copies, that all
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modifications are clearly marked, and that modified versions
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are not represented as the original version unless all the
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modifications since the manual's original release by Ross N.
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Williams (www.ross.net) consist of translations or other
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transformations that alter only the manual's form, not its
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content. THIS MANUAL IS PROVIDED "AS IS" AND WITHOUT ANY
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EXPRESS OR IMPLIED WARRANTIES, INCLUDING, WITHOUT
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LIMITATION, THE IMPLIED WARRANTIES OF MERCHANTIBILITY AND
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FITNESS FOR A PARTICULAR PURPOSE. TO THE EXTENT PERMITTED BY
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<TITLE>6 Tangle</TITLE>
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<A HREF="index.html"><FONT COLOR="#FFFFFF"><B>Reference</B></FONT></A><BR>
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<A HREF="intro.html"><FONT COLOR="#FFFFFF">1 Introduction</FONT></A><BR>
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<A HREF="interface.html"><FONT COLOR="#FFFFFF">2 Interface</FONT></A><BR>
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<A HREF="scanner.html"><FONT COLOR="#FFFFFF">3 Scanner</FONT></A><BR>
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<A HREF="parser.html"><FONT COLOR="#FFFFFF">4 Parser</FONT></A><BR>
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<A HREF="analyser.html"><FONT COLOR="#FFFFFF">5 Analyser</FONT></A><BR>
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<A HREF="tangle.html"><FONT COLOR="#FFFFFF">6 Tangle</FONT></A><BR>
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<A HREF="weave.html"><FONT COLOR="#FFFFFF">7 Weave</FONT></A><BR>
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<A HREF="shell.html"><FONT COLOR="#FFFFFF">8 Shell</FONT></A><BR>
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<A HREF="commands.html"><FONT COLOR="#FFFFFF">9 Commands</FONT></A><BR>
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<A HREF="glossary.html"><FONT COLOR="#FFFFFF">10 Glossary</FONT></A><BR>
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<A HREF="references.html"><FONT COLOR="#FFFFFF">11 References</FONT></A><BR>
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<P><FONT SIZE="5">6 Tangle</FONT><BR>
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<P>If the scanner, parser, and analyser have successfully
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(i.e. with no errors, severe errors, or fatal errors)
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completed, and the Tangle option (<SAMP>+O</SAMP>) is turned on
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(it is by default), then the Tangle component of FunnelWeb
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is invoked to generate the product files specified in the
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<SAMP>@O</SAMP> macros of the input file.
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<P>The operation of Tangle is very simple. Each
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<SAMP>@O</SAMP> macro is expanded and written to a file of the
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same name. As there are a finite number of macros, and the
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analyser guarantees that the macro structure is
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non-recursive, Tangle is guaranteed to terminate.
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<P>Three remaining points are worth mentioning.
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<LI> Tangle expands macros using blank indentation unless
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the user has specified otherwise in an indentation pragma in
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<LI> Tangle keeps track of the length of the lines that
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it is writing and issues an error if any line of any product
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file that it generates is longer than the maximum. The
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maximum is the minimum of a value defaulted or specified in
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the input file, and the value (if any) provided by the
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<SAMP>+w</SAMP> command line argument.
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<LI> If there is more than one macro definition of the
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same name, then each such definition must have a different
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library level (<SAMP>@L</SAMP>). Tangle uses the macro
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definition that has the lowest library level and ignores
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the others completely.
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<P><BR><FONT SIZE="4"><STRONG>Memory Use During Tangling</STRONG></FONT><BR>
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<P>When FunnelWeb executes, it reads each input file (the
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main input file and any include files) into memory where
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they are kept for the duration of the run. This means that
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there must be room in memory for all of the input files.
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This approach is necessary to support FunnelWeb's
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unrestricted forward referencing.
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<P>In contrast, there is no requirement that there be
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enough memory to hold the product files, as these are
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written to disk sequentially during their expansion.
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Furthermore, FunnelWeb does not expand the values of actual
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parameters in memory.
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<P>This means that, so long as the input files fit in
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memory, your product files can be arbitrarily large. You can
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also pass arbitrary large arguments to FunnelWeb macros.
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<A HREF="copyright.html">Copyright © Ross N. Williams 1992,1999. All rights reserved.</A><BR>
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