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FUNNELWEB MANUAL WEB PAGE
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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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LAW THERE IS ABSOLUTELY NO WARRANTY.
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<TITLE>5.2 Wish List</TITLE>
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<A HREF="index.html"><FONT COLOR="#FFFFFF"><B>Developer</B></FONT></A><BR>
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<A HREF="compile.html"><FONT COLOR="#FFFFFF">1 Compile</FONT></A><BR>
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<A HREF="design.html"><FONT COLOR="#FFFFFF">2 Design</FONT></A><BR>
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<A HREF="implement.html"><FONT COLOR="#FFFFFF">3 Implement</FONT></A><BR>
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<A HREF="modify.html"><FONT COLOR="#FFFFFF">4 Modify</FONT></A><BR>
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<A HREF="misc.html"><FONT COLOR="#FFFFFF">5 Misc</FONT></A><BR>
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<A HREF="gpl.html"><FONT COLOR="#FFFFFF">6 Licence</FONT></A><BR>
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<A HREF="search.html"><FONT COLOR="#FFFFFF"><B>SEARCH</B></FONT></A><BR>
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<P><FONT SIZE="5">5.2 Wish List</FONT><BR>
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<P>This page contains the wish list that was included in
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the original 1992 FunnelWeb Hacker's Manual. As hardly any
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changes have been made since then, I thought I'd just
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include it here verbatim.
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<P><BR><FONT SIZE="4"><STRONG>Documentation</STRONG></FONT><BR>
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<P><B>An official example:</B> A official example
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program written using FunnelWeb should be constructed and
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<P><B>Index program:</B> In order to typeset the
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documentation, a portable index sorting program is required.
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One should be written and added to the distribution
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kit. Perhaps this could be the
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<P><BR><FONT SIZE="4"><STRONG>Command Line Interface</STRONG></FONT><BR>
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<P><B>Buffer length:</B> Currently the FunnelWeb
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shell uses the <SAMP>COMLINE_MAX</SAMP> constant to size its
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internal command line buffers. This is untenable. The
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maximum length of a shell command line should not be machine
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<P><B>Antiquated Features:</B> As the FunnelWeb
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language develops, it is likely that some changes will have
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to be made that will render one or more language constructs
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obsolete. When this happens, it may be necessary to add a
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command line option that has the power to turn on and off
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warnings or errors flagging antiquated
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<P><BR><FONT SIZE="4"><STRONG>Shell Interpreter</STRONG></FONT><BR>
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<P><B>SETALL command:</B> When writing FunnelWeb
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scripts, it is sometimes desirable to set <I>all</I> of
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FunnelWeb's options to some particular value
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so that the script is not vulnerable to changes in
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FunnelWeb's default values which might occur from time to
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time. To this end, it may be worth creating a
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"<TT>SETALL</TT>" command that is identical to the
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"<TT>SET</TT>" command except that it will generate an error
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if the value of an option is not specified
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<P><B>Recursion test:</B> A test should be added to
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test for recursive invocation in a
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<P><B>Diagnostic counting:</B> The code for counting
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diagnostics in the script interpreter is rather messy and
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perhaps even buggy. It should be cleaned up and
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<P><B>Argument counting:</B> In the
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<SAMP>command.c</SAMP> module, there is a variable that counts
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the arguments to a command. Currently it takes the value of
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the number of parameters including the command verb. This
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has turned out to make the code less readable. It should be
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changed to be the number of arguments to the command verb.
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<P><B>Make facility:</B> It may be worth building
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some sort of make facility into the script language so as to
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support machines such as the Macintosh that do not already
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<P><B>Signature file:</B> One problem with using
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FunnelWeb in conjunction with an external <SAMP>Make</SAMP>
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facility is that a user might change a FunnelWeb source file
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without making changes that will affect the files that it
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generates. If FunnelWeb is then run and the "<TT>+D</TT>"
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option is on, then the output files will be deleted (to
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avoid further <SAMP>Make</SAMP> propagations). If
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<SAMP>Make</SAMP> then has a production linking the
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<SAMP>.fw</SAMP> file to its output files, then it may conclude
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that the output files are still out of date. To solve the
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problem, FunnelWeb could be changed to write a
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<SAMP>.sig</SAMP> file whenever it processes a <SAMP>.fw</SAMP>
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file. The <SAMP>Make</SAMP> production could then be wired up
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to link the <SAMP>.fw</SAMP> file to the <SAMP>.sig</SAMP> file
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instead of to the output files.
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<P><BR><FONT SIZE="4"><STRONG>Language Design</STRONG></FONT><BR>
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<P>Some proposed changes to FunnelWeb do not correspond to
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any particular component of FunnelWeb and are really to do
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with the design of the input language.
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<P><B>Output or file?:</B> The "<TT>@O</TT>" special
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sequence for defining an output file is somewhat
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non-mnemonic and can be confused with zero ("<TT>0</TT>").
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Perhaps it should be replaced by the "<TT>@F</TT>"
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<P><B>Syntax of section names:</B> Currently section
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names use the same syntax as macro names. For example
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"<TT>@<Sloth@></TT>". It can be argued that angle brackets
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should be reserved only for macro names and that some other
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syntax should be found for delimiting section names. This is
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not a clear issue. It could also be argued that they are
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both names, and that because sections can inherit their
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names from the macros they contain, that the names are of
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<P><B>One macro per section:</B> One particular style
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of using FunnelWeb is to have at most one macro definition
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per section. It may be worth adding a pragma that instructs
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FunnelWeb to enforce this.
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<P><B>Should @\{ suppress EOL?:</B> When defining a
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macro in FunnelWeb, it seems to be rule rather than the
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exception that the "<TT>@\{</TT>" be followed by
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"<TT>@-</TT>". This suppresses the EOL on the definition
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line, allowing the first line of the macro to be placed
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immediately above and in line with the other lines without
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introducing an EOL at the start of the macro text. One
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option is to introduce a pragma to determine whether to
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suppress EOLs following "<TT>@\{</TT>".
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<P><B>Pragma syntax:</B> It is not clear how
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"loose" the syntax of pragmas should be. Perhaps
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they should be case insensitive.
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<P><B>Conditionals:</B> Depending on demand, it may
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be worth reintroducing some sort of conditional feature into
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FunnelWeb. However, it would have to be very simple to
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compete with the various ways in which conditionals can
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already be fudged within FunnelWeb as it
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<P><B>File markers:</B> It might be worth modifying
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the language so that a special syntactical marker is
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required at the start and end of files. This will assist in
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detecting truncations and other
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<P><B>Formal parameter lists:</B> It might be worth
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changing over to a syntax for formal parameter lists that
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does not require the <SAMP>@(</SAMP> and <SAMP>@)</SAMP>.
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However, they could be retained as optional for backward
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<P><BR><FONT SIZE="4"><STRONG>Scanner/Mapper</STRONG></FONT><BR>
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<P><B>All non-contiguous mappings:</B> Currently
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FunnelWeb requires that all input files be mapped into a
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contiguous lump of memory. This caused problems for two
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reasons. First, to do this, one has to allocate the memory
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first, and to do that, you have to know how long the file
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is, and it turns out that finding out the length of a file
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in a portable manner is very inefficient. Second, although
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IBM PC compatibles may have megabytes of memory, it is
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segmented into blocks of at most 64K. This means that
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FunnelWeb currently cannot read a file longer than 64K on a
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These problems could be avoided if the mapper and scanner
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were reorganized to allow input files to be read in and
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stored as a linked list of chunks of text rather than a
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<P><B>EOL is unspecifiable:</B> FunnelWeb uses ASCII
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character decimal ten (10) internally to represent logical
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end-of-line and is currently organized so that if one of
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these is inserted into the text by the user using a
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"<TT>@^D(10)</TT>", it will be written out as
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a logical end of line, rather than as a single ASCII
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character 10. This should be
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<P><B>Allow mnemonics for unprintables:</B> FunnelWeb
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allows users to insert unprintable characters into the
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output using the "<TT>@^D(ddd)</TT>" special
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sequence. Perhaps it would be changed so that it understands
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ASCII standard mnemonics such as "<TT>LF</TT>" as well as
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<P><B>Version pragma:</B> A "<TT>version</TT>" pragma
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should be added that allows the user to specify in the input
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file the version of FunnelWeb that was around when the input
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file was created. At a later date, such a construct would be
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very useful for determining how an input file should be
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updated if the FunnelWeb language has changed between
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<P><BR><FONT SIZE="4"><STRONG>Parser</STRONG></FONT><BR>
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<P>There are no proposals to change the parser except as a
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consequence of other proposals.
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<P><BR><FONT SIZE="4"><STRONG>Analyser</STRONG></FONT><BR>
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<P><B>Recursion detection:</B> Currently the
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FunnelWeb analyser flags, with an error, all macros with an
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infinite expansion. This would be best changed to flagging
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all macros that are directly or indirectly recursive. To do
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this, Tarjan's algorithm<STRONG>[Tarjan72]</STRONG> for the detection of strong components
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<P><B>Once only macros:</B> By default FunnelWeb
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prevents a macro from being called more than once unless it
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has a "<TT>@M</TT>" associated with it. However, FunnelWeb
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does allow a macro that calls such a macro to be called more
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than once. Perhaps this "loophole" should be plugged
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<P><BR><FONT SIZE="4"><STRONG>Tangle</STRONG></FONT><BR>
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<P>The Tangler is one of the cleanest components of
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FunnelWeb, as basically all it has to do is expand some very
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<P><B>Text indentation:</B> Currently FunnelWeb
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supports <I>no indentation</I> and <I>blank
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indentation</I> . A third form could be added if it was
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considered necessary. <I>Text indentation</I> is the same
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as <I>blank indentation</I> except that instead of
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indenting with blanks, FunnelWeb would indent with the text
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to the left of the called macro. This facility could be
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useful for commenting out large bodies of text in languages
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that do not have multi-line comments (e.g. Ada). A
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discussion of the pros and cons of this form of indentation
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<P><BR><FONT SIZE="4"><STRONG>Weave</STRONG></FONT><BR>
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<P>Perhaps FunnelWeb's weakest aspect is its typesetting
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<P><B>Align table of contents:</B> When FunnelWeb
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generates a table of contents, the section numbers are not
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quite aligned with the start of the controlling heading
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<P><B>Typesetting strength:</B> It should be possible
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to specify the level of typesetting strength for headings so
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that short documents do not look overdone when typeset. A
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new pragma would be good for
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<P><B>Typeset a portion:</B> Sometimes it is
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desirable to typeset just a portion of a program. A command
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line option could be added to do this. The option could
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accept as its argument, a string containing a list of
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section numbers or heading names.
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<P><B>Generic typesetter option:</B> In addition to
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building in a number of different versions of Weave, one for
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each popular typesetter, it would be possible to add a
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special generic format where the typeset output is expressed
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in terms of <I>FunnelWeb macros</I> . The user could then
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specify macro definitions for a non-supported typesetter and
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run the output through FunnelWeb Tangle to get a typeset
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file in a format suitable for the unsupported
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<P><B>Suppression of include files:</B> It should be
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possible to specify in the input file that particular
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included files not appear in the typeset output. Currently,
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the fact that an inclusion has occurred is not even
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represented in the typeset output. Suppression of inclusions
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is particularly necessary where a library of macros has been
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included at the top of each of a group of source
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<P><B>Cross reference of identifiers:</B> WEB
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provides a list of identifiers and a list of all the
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definitions in which they are used. A similar feature could
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be added to FunnelWeb.
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<P><B>Support for non-printables:</B> Currently
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FunnelWeb does not provide support for typesetting the
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special "<TT>@\circumflex(num)</TT>" sequences. This should
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<P><B>Support for @+ sequences:</B> Currently Weave
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does not see "<TT>@+</TT>" sequences as such. Instead it
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perceives them as ordinary EOLs. However, there are
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arguments for typesetting them specially.
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<P><B>Typeset text in macro bodies:</B> One of the
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much-loved features of WEB is the way that it allows the
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user to switch recursively between document and program
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formats. FunnelWeb does not allow this, but should. In
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FunnelWeb, the delimiters "<TT>@{</TT>" and
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"<TT>@}</TT>" are already used consistently to delimit
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macro text. The "<TT>@[</TT>" and "<TT>@]</TT>" sequences
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have been reserved for the delimitation of documentation
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<P><B>Non-tt typesetting:</B> The current version of
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FunnelWeb sets all its macro text in <SAMP>tt font</SAMP>. This
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is both a blessing and a curse. It is a blessing because it
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connects the reader directly to the code, with no
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complicated intermediary. It is a curse because it looks
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ugly compared to the beautifully typeset programs produced
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by other literate programming tools.
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<P>The difficulty with adding such beautiful typesetting is
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that it is necessarily language-specific. Keywords and
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syntax differ from language to language and it would not be
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easy to come up with a set of language independent rules.
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<P>One approach is to write a set of Weave back-ends, one for
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each language. Another approach is to <I>generate</I> back
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ends. This is the approach taken in the <I>Spider</I>
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system<STRONG>[Ramsey89]</STRONG>. In the
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<I>Spider</I> system, the programmer writes production
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rules for converting lexical components of the program text
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into typesetter instructions. The <I>Spider</I> program
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reads these rules and generates a new version of WEB suited
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for the target language.
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<P>For FunnelWeb a slightly different system is proposed in
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which Spider-like rules appear in the input file and are
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used directly by Weave to perform the typesetting. An
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intermediate abstract typesetting language could be used so
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that the productions can be made language specific, but not
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<P><BR><FONT SIZE="4"><STRONG>Lister</STRONG></FONT><BR>
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<P><B>Glue factor:</B> A glue factor could be added
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that determines how many lines can be in between two
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diagnostics in the listing before the two groups of lines
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are joined together in the listing with no intervening
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<P><BR><FONT SIZE="4"><STRONG>Diagnostics</STRONG></FONT><BR>
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<P><B>Advisory information:</B> Some of FunnelWeb's
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diagnostics provide a detailed explanatory paragraph. While
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this information might be useful the first time, it has the
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capacity to clog up a listing file if the user has made the
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same error many times. To solve this problem, FunnelWeb
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could be modified so that such explanations are only
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displayed the first time the error occurs.
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<P><B>Abort after n errors:</B> A facility could be
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added to prevent FunnelWeb's scanning, parsing, and
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analysing phases from continuing if a certain number of
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errors have already been issued.
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<P><BR><FONT SIZE="4"><STRONG>Speed</STRONG></FONT><BR>
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<P><B>Measurement of speed:</B> Although FunnelWeb
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can generate a breakdown of where it is spending its time,
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it does not give a final rating in lines per minute. This
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<P><B>Find the hot spots:</B> Although FunnelWeb has
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been designed to allow high speed, not much effort has so
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far been made to make it fast. This should be done.
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<P><B>Change some declarations:</B> FunnelWeb is full
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of variable declarations where the variables are wider than
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they need be. Replacing these might speed it up.
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<P><BR><FONT SIZE="4"><STRONG>Correctness</STRONG></FONT><BR>
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<P><B>Bounds analysis:</B> Not much effort has gone
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into the design of FunnelWeb's input boundaries. An analysis
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should be made of FunnelWeb's behaviour when the following
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quantities are stretched:
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<LI> Input line length.
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<LI> Input file size.
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<LI> Number of macros.
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<LI> Length of macro.
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<P>In particular, FunnelWeb's behaviour at 32K and 64K
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boundaries should be observed.
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<P><B>Stack detection:</B> Macintosh THINK-C provides
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just 6K of memory for the stack. It might be worth adding
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checks to make sure that the stack is not being blown.
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<P><BR><FONT SIZE="4"><STRONG>Test Suite</STRONG></FONT><BR>
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<P>The following tests should be added to the test suite:
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LR01: Test with a full listing with no diagnostics.
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LR02: Test with a full listing with diagnostics.
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LR03: Test abbreviated listing with no diagnostics.
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LR04: Test abbreviated listing with diagnostics.
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LR05: Test error context with nearby diagnostics.
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Static analysis might preclude the need for
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BC01: Test what happens when memory runs out.
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BC02: File with a single line of a megabyte.
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BC03: File of a megabyte of EOLs.
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BC04: Output file with an extremely long line.
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BC05: Output file with one million lines.
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BC06: Test on a file with very many macros.
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GN01: A large legal input file exercising
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as many features as possible.
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1. Test listing file.
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2. Test output files.
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3. Test typeset file.
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GN... A selection of ten real-life FunnelWeb files.
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<P><BR><FONT SIZE="4"><STRONG>Platform-Specific Changes</STRONG></FONT><BR>
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<P><B>Icon for the Macintosh:</B> Currently no icon
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is supplied for the Macintosh version of FunnelWeb. An icon
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depicting a spider or a funnelled web of some kind would
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<A HREF="copyright.html">Copyright © Ross N. Williams 1992,1999. All rights reserved.</A><BR>
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