#LyX 1.6.0 created this file. For more info see http://www.lyx.org/
\lyxformat 345
\begin_document
\begin_header
\use_default_options false
\textclass literate-article
\begin_preamble
%
% This relaxes the noweb constraint that chunks are
% never broken across pages.
%
% This is from the noweb FAQ
%
\def\nwendcode{\endtrivlist \endgroup}
\let\nwdocspar=\smallbreak
\end_preamble
\language english
\inputencoding default
\font_roman default
\font_sans default
\font_typewriter default
\font_default_family default
\font_sc false
\font_osf false
\font_sf_scale 100
\font_tt_scale 100
\graphics default
\paperfontsize default
\spacing single
\use_hyperref false
\papersize default
\use_geometry false
\use_amsmath 0
\use_esint 0
\cite_engine basic
\use_bibtopic false
\paperorientation portrait
\secnumdepth 3
\tocdepth 3
\paragraph_separation indent
\defskip medskip
\quotes_language english
\papercolumns 1
\papersides 1
\paperpagestyle default
\tracking_changes false
\output_changes false
\author ""
\end_header

\begin_body

\begin_layout Title

\noun on
noweb2lyx
\end_layout

\begin_layout Author
Kayvan A.
 Sylvan <kayvan@sylvan.com>
\end_layout

\begin_layout Date
May 6, 1999
\end_layout

\begin_layout Abstract
This document describes and implements a perl script for importing noweb
 files into LyX
\end_layout

\begin_layout Standard
\begin_inset CommandInset toc
LatexCommand tableofcontents

\end_inset


\end_layout

\begin_layout Standard
\begin_inset Newpage newpage
\end_inset


\end_layout

\begin_layout Section
Introduction
\end_layout

\begin_layout Standard
Since version 1.0.1, LyX now supports Literate Programming using 
\noun on
noweb
\noun default
.
 This addition to LyX made it very pleasant to write programs in the literate
 style (like this one).
 In addition to being able to write new literate programs, it would be quite
 useful if old 
\noun on
noweb
\noun default
 code could be imported into LyX in some fashion.
 That's where this program comes in.
\end_layout

\begin_layout Standard
The purpose of 
\noun on
noweb2lyx
\noun default
 is to convert a 
\noun on
noweb
\noun default
 file to LyX.
\end_layout

\begin_layout Scrap
<<noweb2lyx.in>>=
\begin_inset Newline newline
\end_inset

#!@PERL@
\begin_inset Newline newline
\end_inset

# 
\begin_inset Newline newline
\end_inset

# Copyright (C) 1999 Kayvan A.
 Sylvan <kayvan@sylvan.com>
\begin_inset Newline newline
\end_inset

# You are free to use and modify this code under the terms of
\begin_inset Newline newline
\end_inset

# the GNU General Public Licence version 2 or later.
\begin_inset Newline newline
\end_inset

#
\begin_inset Newline newline
\end_inset

# Written with assistance from:
\begin_inset Newline newline
\end_inset

#   Edmar Wienskoski Jr.
 <edmar-w-jr@technologist.com>
\begin_inset Newline newline
\end_inset

#   Amir Karger <karger@post.harvard.edu>
\begin_inset Newline newline
\end_inset

#
\begin_inset Newline newline
\end_inset

# $Id: noweb2lyx.lyx,v 1.5 2005/07/18 09:42:27 jamatos Exp $
\begin_inset Newline newline
\end_inset

#
\begin_inset Newline newline
\end_inset

# NOTE: This file was automatically generated from noweb2lyx.lyx using noweb.
\begin_inset Newline newline
\end_inset

#
\begin_inset Newline newline
\end_inset

<<Setup variables from user supplied args>>
\begin_inset Newline newline
\end_inset

<<Subroutines>>
\begin_inset Newline newline
\end_inset

<<Convert noweb to LyX>>
\begin_inset Newline newline
\end_inset

@
\end_layout

\begin_layout Section
The Noweb file defined
\end_layout

\begin_layout Standard
A 
\noun on
noweb
\noun default
 file is a collection of documentation and code chunks.
 Documentation chunks simply start with an ``@'' and have no name:
\end_layout

\begin_layout LyX-Code
@ Here is some documentation.
\begin_inset Newline newline
\end_inset

We can do arbitrary LaTeX code here.
\begin_inset Newline newline
\end_inset

[...
 blah blah blah ...]
\end_layout

\begin_layout Standard
Code chunks look like this:
\end_layout

\begin_layout LyX-Code
<
\begin_inset ERT
status collapsed

\begin_layout Plain Layout

{}
\end_layout

\end_inset

<Name of chunk here>
\begin_inset ERT
status collapsed

\begin_layout Plain Layout

{}
\end_layout

\end_inset

>=
\begin_inset Newline newline
\end_inset

{...
 code for the chunk goes here ...}
\begin_inset Newline newline
\end_inset

@ 
\end_layout

\begin_layout Standard
The ``@'' is a necessary delimiter to end the code chunk.
 The other form that the ``@'' line takes is as follows:
\end_layout

\begin_layout LyX-Code
<
\begin_inset ERT
status collapsed

\begin_layout Plain Layout

{}
\end_layout

\end_inset

<Name of chunk here>
\begin_inset ERT
status collapsed

\begin_layout Plain Layout

{}
\end_layout

\end_inset

>=
\begin_inset Newline newline
\end_inset

{...
 code for the chunk ...}
\begin_inset Newline newline
\end_inset

@ %def identifier1 identifier2
\end_layout

\begin_layout Standard
In the latter form, we are declaring to 
\noun on
noweb
\noun default
 that this code chunk defines identifier1, identifier2, etc.
\end_layout

\begin_layout Standard
When first tackling this problem, I spoke with members of the LyX team that
 knew about the literate programming extensions and reLyX (the LaTeX importing
 code).
\end_layout

\begin_layout Standard
One of the first ideas was to extend the reLyX code to understand the 
\noun on
noweb
\noun default
 code chunks.
 This proved to be too hard and presents other problems
\begin_inset Foot
status collapsed

\begin_layout Plain Layout
Not the least of these problems is the fact that << is a quote in French.
\end_layout

\end_inset

.
 On the other hand, it turns out that reLyX contains a very useful literal
 quoting mechanism.
 If the input file contains the construct
\end_layout

\begin_layout LyX-Code

\backslash
begin{reLyXskip}
\begin_inset Newline newline
\end_inset

{...
 LaTeX stuff ...}
\begin_inset Newline newline
\end_inset


\backslash
end{reLyXskip}
\end_layout

\begin_layout Standard
then reLyX will copy the surrounded code to the output file verbatim.
 Given this, the first part of the translation is easy; we simply have to
 copy the code chunks into an intermediate file that surrounds them with
 
\family typewriter

\backslash
begin{reLyXskip}
\family default
 and 
\family typewriter

\backslash
end{reLyXskip}
\family default
.
\end_layout

\begin_layout Standard
Once reLyX is done with the input file, the problem is reduced to changing
 the code chunks from LyX's LaTeX layout to the Scrap layout.
\end_layout

\begin_layout Standard
There is one final constraint on 
\noun on
noweb2lyx
\noun default
.
 We want to be able to run it as a simple pre-processor and post-processor
 from within reLyX.
 We can accomplish this by setting the flags 
\family roman
\series medium
\shape up
\size normal
\emph off
\bar no
\noun off
\color none

\begin_inset ERT
status collapsed

\begin_layout Plain Layout

[[pre_only]]
\end_layout

\end_inset


\family default
\series default
\shape default
\size default
\emph default
\bar default
\noun default
 
\color inherit
and
\color none
 
\family roman
\series medium
\shape up
\size normal
\emph off
\bar no
\noun off

\begin_inset ERT
status collapsed

\begin_layout Plain Layout

[[post_only]]
\end_layout

\end_inset


\family default
\series default
\shape default
\size default
\emph default
\bar default
\noun default
 
\color inherit
before we reach the main conversion code.
\end_layout

\begin_layout Standard
With all that preamble out of the way, we now have the basic high-level
 outline for our code:
\end_layout

\begin_layout Scrap
<<Convert noweb to LyX>>=
\begin_inset Newline newline
\end_inset

if (!$post_only) {
\begin_inset Newline newline
\end_inset

  <<Transform noweb for reLyX>>
\begin_inset Newline newline
\end_inset

}
\begin_inset Newline newline
\end_inset

if ((!$pre_only) && (!$post_only)) {
\begin_inset Newline newline
\end_inset

  <<Run reLyX on intermediate file>>
\begin_inset Newline newline
\end_inset

}
\begin_inset Newline newline
\end_inset

if (!$pre_only) {
\begin_inset Newline newline
\end_inset

  <<Fix up LyX file>>
\begin_inset Newline newline
\end_inset

}
\begin_inset Newline newline
\end_inset

<<Clean up>>
\begin_inset Newline newline
\end_inset

@
\end_layout

\begin_layout Section
Making a file that reLyX can process
\end_layout

\begin_layout Standard
In this section, we present the code that performs the task of creating
 the intermediate file that reLyX can process, using the algorithm that
 we just outlined.
 This algorithm is outlined in the code that follows:
\end_layout

\begin_layout Scrap
<<Transform noweb for reLyX>>=
\begin_inset Newline newline
\end_inset

<<Setup INPUT and OUTPUT>>
\begin_inset Newline newline
\end_inset

inputline: while(<INPUT>)
\begin_inset Newline newline
\end_inset

{
\begin_inset Newline newline
\end_inset

  if (/^
\backslash
s*
\backslash
<
\backslash
<.*
\backslash
>
\backslash
>=/) { # Beginning of a noweb scrap
\begin_inset Newline newline
\end_inset

    <<Read in and output the noweb code chunk>>
\begin_inset Newline newline
\end_inset

  } elsif (/^@
\backslash
s+(.*)/) { # Beginning of a documentation chunk
\begin_inset Newline newline
\end_inset

    print OUTPUT $1; # We do not need the ``@'' part
\begin_inset Newline newline
\end_inset

  } elsif (/
\backslash
[
\backslash
[.+
\backslash
]
\backslash
]/) { # noweb quoted code
\begin_inset Newline newline
\end_inset

    <<Perform special input quoting of [[var]]>>
\begin_inset Newline newline
\end_inset

  } else {
\begin_inset Newline newline
\end_inset

    print OUTPUT; # Just let the line pass through
\begin_inset Newline newline
\end_inset

  }
\begin_inset Newline newline
\end_inset

}
\begin_inset Newline newline
\end_inset

<<Close INPUT and OUTPUT>>
\begin_inset Newline newline
\end_inset

@
\end_layout

\begin_layout Standard
In the code above, we do some pre-processing of the noweb ``[[...]]'' construct.
 This avoids some problems with reLyX confusing lists composed of ``[[...]]''
 constructs.
\end_layout

\begin_layout Scrap
<<Perform special input quoting of [[var]]>>=
\begin_inset Newline newline
\end_inset

s/
\backslash
[
\backslash
[.+?
\backslash
]{2,}/{$&}/g;
\begin_inset Newline newline
\end_inset

print OUTPUT;
\begin_inset Newline newline
\end_inset

@
\end_layout

\begin_layout Standard
While reading in the 
\family roman
\series medium
\shape up
\size normal
\emph off
\bar no
\noun off
\color none

\begin_inset ERT
status collapsed

\begin_layout Plain Layout

[[INPUT]]
\end_layout

\end_inset


\family default
\series default
\shape default
\size default
\emph default
\bar default
\noun default
 
\color inherit
file, once we have identified a 
\noun on
noweb
\noun default
 code chunk, we transform it into a form that is usable by reLyX.
\end_layout

\begin_layout Scrap
<<Read in and output the noweb code chunk>>= 
\begin_inset Newline newline
\end_inset

<<Save the beginning of the scrap to savedScrap>>
\begin_inset Newline newline
\end_inset

<<Concatenate the rest of the scrap>>
\begin_inset Newline newline
\end_inset

<<print out the scrap in a reLyXskip block>>
\begin_inset Newline newline
\end_inset

@
\end_layout

\begin_layout Subsection
File input and output for the pre-processing step
\end_layout

\begin_layout Standard
In 
\noun on
noweb2lyx
\noun default
, we will use 
\family roman
\series medium
\shape up
\size normal
\emph off
\bar no
\noun off
\color none

\begin_inset ERT
status collapsed

\begin_layout Plain Layout

[[INPUT]]
\end_layout

\end_inset


\family default
\series default
\shape default
\size default
\emph default
\bar default
\noun default
 
\color inherit
and
\color none
 
\family roman
\series medium
\shape up
\size normal
\emph off
\bar no
\noun off

\begin_inset ERT
status collapsed

\begin_layout Plain Layout

[[OUTPUT]]
\end_layout

\end_inset


\family default
\series default
\shape default
\size default
\emph default
\bar default
\noun default
 
\color inherit
to read and write files.
 In the code fragment above, we need to read from the input file and write
 to a file that will be later transformed by reLyX.
 If we are being called only to pre-process the input file, then there is
 no need to create a temporary file.
\end_layout

\begin_layout Scrap
<<Setup INPUT and OUTPUT>>=
\begin_inset Newline newline
\end_inset

if ($pre_only) {
\begin_inset Newline newline
\end_inset

  &setup_files($input_file, $output_file);
\begin_inset Newline newline
\end_inset

} else {
\begin_inset Newline newline
\end_inset

  $relyx_file = "temp$$";
\begin_inset Newline newline
\end_inset

  &setup_files($input_file, $relyx_file);
\begin_inset Newline newline
\end_inset

}
\begin_inset Newline newline
\end_inset

@
\end_layout

\begin_layout Standard
This code uses a small perl subroutine, 
\family roman
\series medium
\shape up
\size normal
\emph off
\bar no
\noun off
\color none

\begin_inset ERT
status collapsed

\begin_layout Plain Layout

[[setup_files]]
\end_layout

\end_inset


\family default
\series default
\shape default
\size default
\emph default
\bar default
\noun default
\color inherit
, which we define below:
\end_layout

\begin_layout Scrap
<<Subroutines>>=
\begin_inset Newline newline
\end_inset

sub setup_files {
\begin_inset Newline newline
\end_inset

  my($in, $out) = @_;
\begin_inset Newline newline
\end_inset

  open(INPUT, "<$in") || die "Cannot read $in: $!
\backslash
n";
\begin_inset Newline newline
\end_inset

  open(OUTPUT, ">$out") || die "Cannot write $out: $!
\backslash
n";
\begin_inset Newline newline
\end_inset

}
\begin_inset Newline newline
\end_inset

@ %def setup_files   
\end_layout

\begin_layout Subsection
Reading in the 
\noun on
noweb
\noun default
 scrap
\end_layout

\begin_layout Standard
After we see the beginning of the scrap, we need to read in and save the
 rest of the scrap for output.
\end_layout

\begin_layout Scrap
<<Save the beginning of the scrap to savedScrap>>=
\begin_inset Newline newline
\end_inset

$savedScrap = $_;
\begin_inset Newline newline
\end_inset

$endLine = "";
\begin_inset Newline newline
\end_inset

@
\end_layout

\begin_layout Scrap
<<Concatenate the rest of the scrap>>=
\begin_inset Newline newline
\end_inset

scrapline: while (<INPUT>) {
\begin_inset Newline newline
\end_inset

  last scrapline if /^@
\backslash
s+/;
\begin_inset Newline newline
\end_inset

  $savedScrap .= $_;
\begin_inset Newline newline
\end_inset

};
\begin_inset Newline newline
\end_inset

switch: {
\begin_inset Newline newline
\end_inset

  if (/^@
\backslash
s+$/) {$savedScrap .= $_; last switch; }
\begin_inset Newline newline
\end_inset

  if (/^@
\backslash
s+%def.*$/) {$savedScrap .= $_; last switch; }
\begin_inset Newline newline
\end_inset

  if (/^@
\backslash
s+(.*)$/) {$savedScrap .= "@
\backslash
n"; $endLine = "$1
\backslash
n"; }
\begin_inset Newline newline
\end_inset

}
\begin_inset Newline newline
\end_inset

@
\end_layout

\begin_layout Subsection
Printing out the scrap
\end_layout

\begin_layout Standard
The final piece of the first pass of the conversion is done by this code.
\end_layout

\begin_layout Scrap
<<print out the scrap in a reLyXskip block>>=
\begin_inset Newline newline
\end_inset

print OUTPUT "
\backslash

\backslash
begin{reLyXskip}
\backslash
n";
\begin_inset Newline newline
\end_inset

print OUTPUT $savedScrap;
\begin_inset Newline newline
\end_inset

print OUTPUT "
\backslash

\backslash
end{reLyXskip}
\backslash
n
\backslash
n";
\begin_inset Newline newline
\end_inset

print OUTPUT "$endLine";
\begin_inset Newline newline
\end_inset

@
\end_layout

\begin_layout Standard
Finally, we need to close the 
\family roman
\series medium
\shape up
\size normal
\emph off
\bar no
\noun off
\color none

\begin_inset ERT
status collapsed

\begin_layout Plain Layout

[[INPUT]]
\end_layout

\end_inset


\family default
\series default
\shape default
\size default
\emph default
\bar default
\noun default
 
\color inherit
and
\color none
 
\family roman
\series medium
\shape up
\size normal
\emph off
\bar no
\noun off

\begin_inset ERT
status collapsed

\begin_layout Plain Layout

[[OUTPUT]]
\end_layout

\end_inset


\family default
\series default
\shape default
\size default
\emph default
\bar default
\noun default
 
\color inherit
files.
\end_layout

\begin_layout Scrap
<<Close INPUT and OUTPUT>>=
\begin_inset Newline newline
\end_inset

close(INPUT);
\begin_inset Newline newline
\end_inset

close(OUTPUT);
\begin_inset Newline newline
\end_inset

@
\end_layout

\begin_layout Section
Running reLyX
\end_layout

\begin_layout Standard
In this section, we describe and implement the code that runs reLyX on the
 intermediate file 
\family roman
\series medium
\shape up
\size normal
\emph off
\bar no
\noun off
\color none

\begin_inset ERT
status collapsed

\begin_layout Plain Layout

[[relyx_file]]
\end_layout

\end_inset


\family default
\series default
\shape default
\size default
\emph default
\bar default
\noun default
\color inherit
.
 
\end_layout

\begin_layout Subsection
Selecting the document class
\end_layout

\begin_layout Standard
In order to run reLyX, we need to know the article class of the input document
 (to choose the corresponding literate document layout).
 For this, we need to parse the intermediate file.
\end_layout

\begin_layout Scrap
<<Run reLyX on intermediate file>>=
\begin_inset Newline newline
\end_inset

<<Parse for document class>>
\begin_inset Newline newline
\end_inset

<<Run reLyX with document class>>
\begin_inset Newline newline
\end_inset

@
\end_layout

\begin_layout Standard
In the code below, you'll see a strange regular expression to search for
 the document class.
 The reason for this kludge is that without it, we can't run 
\noun on
noweb2lyx
\noun default
 on the 
\emph on
noweb2lyx.nw
\emph default
 file that is generated by LyX
\begin_inset Foot
status collapsed

\begin_layout Plain Layout
reLyX searches for 
\backslash

\backslash
doc
\family roman
\series medium
\shape up
\size normal
\emph off
\bar no
\noun off
\color none

\begin_inset ERT
status collapsed

\begin_layout Plain Layout

{}
\end_layout

\end_inset


\family default
\series default
\shape default
\size default
\emph default
\bar default
\noun default
\color inherit
ument
\family roman
\series medium
\shape up
\size normal
\emph off
\bar no
\noun off
\color none

\begin_inset ERT
status collapsed

\begin_layout Plain Layout

{}
\end_layout

\end_inset


\family default
\series default
\shape default
\size default
\emph default
\bar default
\noun default
\color inherit
class and gets confused, so we have to obfuscate it slightly.
\end_layout

\end_inset

.
 With the regular expression as it is, we can actually run 
\noun on
noweb2lyx
\noun default
 on itself and a produce a quite reasonable LyX file.
\end_layout

\begin_layout Scrap
<<Parse for document class>>=
\begin_inset Newline newline
\end_inset

open(INPUT, "<$relyx_file") ||
\begin_inset Newline newline
\end_inset

  die "Cannot read $relyx_file: $!
\backslash
n";
\begin_inset Newline newline
\end_inset

$class = "article"; # default if none found
\begin_inset Newline newline
\end_inset

parse: while(<INPUT>) {
\begin_inset Newline newline
\end_inset

  if (/
\backslash

\backslash
docu[m]entclass{(.*)}/) {
\begin_inset Newline newline
\end_inset

    $class = $1;
\begin_inset Newline newline
\end_inset

    last parse;
\begin_inset Newline newline
\end_inset

  }
\begin_inset Newline newline
\end_inset

}
\begin_inset Newline newline
\end_inset

close(INPUT);
\begin_inset Newline newline
\end_inset

@
\end_layout

\begin_layout Subsection
Running reLyX with the corresponding literate document layout
\end_layout

\begin_layout Standard
Now that we know what the document class ought to be, we do:
\end_layout

\begin_layout Scrap
<<Run reLyX with document class>>= 
\begin_inset Newline newline
\end_inset

$doc_class = "literate-" .
 $class;
\begin_inset Newline newline
\end_inset

die "reLyX returned non-zero: $!
\backslash
n"
\begin_inset Newline newline
\end_inset

  if (system("reLyX -c $doc_class $relyx_file"));
\begin_inset Newline newline
\end_inset

@
\end_layout

\begin_layout Standard
reLyX performs the main bulk of the translation work.
 Note that if the ``literate-
\emph on
class
\emph default
'' document layout is not found, then reLyX will fail with an error.
 In that case, you may need to modify your 
\noun on
noweb
\noun default
 input file to a supported document type.
\end_layout

\begin_layout Section
Fixing the reLyX output
\end_layout

\begin_layout Standard
We need to perform some post-processing of what reLyX produces in order
 to have the best output for our literate document.
 The outline of the post-processing steps are:
\end_layout

\begin_layout Scrap
<<Fix up LyX file>>=
\begin_inset Newline newline
\end_inset

<<Setup INPUT and OUTPUT for the final output>>
\begin_inset Newline newline
\end_inset

line: while(<INPUT>)
\begin_inset Newline newline
\end_inset

{
\begin_inset Newline newline
\end_inset

  <<Fix code chunks in latex layout>>
\begin_inset Newline newline
\end_inset

  <<Fix [[var]] noweb construct>>
\begin_inset Newline newline
\end_inset

  print OUTPUT; # default
\begin_inset Newline newline
\end_inset

} 
\begin_inset Newline newline
\end_inset

<<Close INPUT and OUTPUT>>
\begin_inset Newline newline
\end_inset

@
\end_layout

\begin_layout Standard
Note that in the perl code that is contained in the 
\family roman
\series medium
\shape up
\size normal
\emph off
\bar no
\noun off
\color none

\begin_inset ERT
status collapsed

\begin_layout Plain Layout

[[while(<INPUT>)]]
\end_layout

\end_inset


\family default
\series default
\shape default
\size default
\emph default
\bar default
\noun default
 
\color inherit
loop above, the perl construct
\color none
 
\family roman
\series medium
\shape up
\size normal
\emph off
\bar no
\noun off

\begin_inset ERT
status collapsed

\begin_layout Plain Layout

[[next line]]
\end_layout

\end_inset


\family default
\series default
\shape default
\size default
\emph default
\bar default
\noun default
 
\color inherit
is sufficient to restart the loop.
 We can use this construct to do some relatively complex parsing of the
 reLyX generated file.
\end_layout

\begin_layout Subsection
File input and output for the post-processing
\end_layout

\begin_layout Standard
Setting up the 
\family roman
\series medium
\shape up
\size normal
\emph off
\bar no
\noun off
\color none

\begin_inset ERT
status collapsed

\begin_layout Plain Layout

[[INPUT]]
\end_layout

\end_inset


\family default
\series default
\shape default
\size default
\emph default
\bar default
\noun default
 
\color inherit
and
\color none
 
\family roman
\series medium
\shape up
\size normal
\emph off
\bar no
\noun off

\begin_inset ERT
status collapsed

\begin_layout Plain Layout

[[OUTPUT]]
\end_layout

\end_inset


\family default
\series default
\shape default
\size default
\emph default
\bar default
\noun default
 
\color inherit
is taken care of by this code:
\end_layout

\begin_layout Scrap
<<Setup INPUT and OUTPUT for the final output>>=
\begin_inset Newline newline
\end_inset

if ($post_only) {
\begin_inset Newline newline
\end_inset

  &setup_files("$input_file", "$output_file");
\begin_inset Newline newline
\end_inset

} else {
\begin_inset Newline newline
\end_inset

  &setup_files("$relyx_file.lyx", "$output_file");
\begin_inset Newline newline
\end_inset

}
\begin_inset Newline newline
\end_inset

@
\end_layout

\begin_layout Subsection
Making sure the code chunks are in the Scrap layout
\end_layout

\begin_layout Standard
Now, as we outlined before, the final step is transforming the code-chunks
 which have been put into a LaTeX layout by LyX into the scrap layout.
\end_layout

\begin_layout Scrap
<<Fix code chunks in latex layout>>=
\begin_inset Newline newline
\end_inset

if (/
\backslash

\backslash
latex latex/) { # Beginning of some latex code
\begin_inset Newline newline
\end_inset

  if (($line = <INPUT>) =~ /^
\backslash
s*<</) { # code scrap
\begin_inset Newline newline
\end_inset

    <<Transform this chunk into layout scrap>>
\begin_inset Newline newline
\end_inset

  } else {
\begin_inset Newline newline
\end_inset

    # print the 
\backslash
latex latex line + next line
\begin_inset Newline newline
\end_inset

    print OUTPUT "$_$line";
\begin_inset Newline newline
\end_inset

  }
\begin_inset Newline newline
\end_inset

  next line;
\begin_inset Newline newline
\end_inset

}
\begin_inset Newline newline
\end_inset

@
\end_layout

\begin_layout Standard
When we are sure that we are in a code chunk, we must read in the rest of
 the code chunk and output a scrap layout for it:
\end_layout

\begin_layout Scrap
<<Transform this chunk into layout scrap>>=
\begin_inset Newline newline
\end_inset

$savedScrap = "
\backslash

\backslash
layout Scrap
\backslash
n
\backslash
n$line";
\begin_inset Newline newline
\end_inset

codeline: while (<INPUT>) {
\begin_inset Newline newline
\end_inset

  $savedScrap .= $_;
\begin_inset Newline newline
\end_inset

  last codeline if /^@
\backslash
s+/;
\begin_inset Newline newline
\end_inset

};
\begin_inset Newline newline
\end_inset

print OUTPUT $savedScrap;
\begin_inset Newline newline
\end_inset

<<Slurp up to the end of the latex layout>>
\begin_inset Newline newline
\end_inset

@
\end_layout

\begin_layout Standard
Okay, now we just need to eat the rest of the latex layout.
 There should only be a few different types of lines for us to match:
\end_layout

\begin_layout Scrap
<<Slurp up to the end of the latex layout>>=
\begin_inset Newline newline
\end_inset

slurp: while (<INPUT>) {
\begin_inset Newline newline
\end_inset

  last slurp if /
\backslash

\backslash
latex /;
\begin_inset Newline newline
\end_inset

  next slurp if /
\backslash

\backslash
newline/;
\begin_inset Newline newline
\end_inset

  next slurp if /^
\backslash
s*$/;
\begin_inset Newline newline
\end_inset

  warn "confused by line: $_";
\begin_inset Newline newline
\end_inset

}
\begin_inset Newline newline
\end_inset

@
\end_layout

\begin_layout Subsection
Taking care of the 
\noun on
noweb
\noun default
 
\emph on
[[quoted code]]
\emph default
 construct
\end_layout

\begin_layout Standard

\noun on
noweb
\noun default
 allows the user to use a special code quoting mechanism in documentation
 chunks.
 Fixing this ``[[quoted-code]]'' 
\noun on
noweb
\noun default
 syntax means putting the ``[[quoted-code]]'' in a LaTeX layout in the LyX
 file.
 Otherwise, LyX will backslash-quote the brackets, creating ugly output.
 The quoted-code is transformed by 
\noun on
noweb
\noun default
 when it generates the final LaTeX code.
\end_layout

\begin_layout Scrap
<<Fix [[var]] noweb construct>>=
\begin_inset Newline newline
\end_inset

if (/
\backslash
[
\backslash
[.+
\backslash
]
\backslash
]/) { # special code for [[var]]
\begin_inset Newline newline
\end_inset

  s/
\backslash
[
\backslash
[.+?
\backslash
]{2,}/
\backslash
n
\backslash

\backslash
latex latex
\backslash
n$&
\backslash
n
\backslash

\backslash
latex default
\backslash
n/g;
\begin_inset Newline newline
\end_inset

  print OUTPUT;
\begin_inset Newline newline
\end_inset

  next line;
\begin_inset Newline newline
\end_inset

}
\begin_inset Newline newline
\end_inset

@
\end_layout

\begin_layout Section
Cleaning up intermediate files
\end_layout

\begin_layout Standard
The cleanup code is very simple:
\end_layout

\begin_layout Scrap
<<Clean up>>=
\begin_inset Newline newline
\end_inset

system("rm -f $relyx_file*") unless ($post_only || $pre_only);
\begin_inset Newline newline
\end_inset

@
\end_layout

\begin_layout Section
User supplied arguments
\end_layout

\begin_layout Standard
The 
\noun on
noweb2lyx
\noun default
 script understands two arguments, input-file and output-file.
 It is also set up to be used internally by reLyX to pre-process or postprocess
 files in the import pipeline.
\end_layout

\begin_layout Scrap
<<Setup variables from user supplied args>>=
\begin_inset Newline newline
\end_inset

&usage() if ($#ARGV < 1); # zero or one argument 
\begin_inset Newline newline
\end_inset

if ($ARGV[0] eq "-pre") {
\begin_inset Newline newline
\end_inset

  &usage unless ($#ARGV == 2);
\begin_inset Newline newline
\end_inset

  $input_file = $ARGV[1]; $output_file = $ARGV[2]; $pre_only = 1;
\begin_inset Newline newline
\end_inset

} elsif ($ARGV[0] eq "-post") {
\begin_inset Newline newline
\end_inset

  &usage unless ($#ARGV == 2);
\begin_inset Newline newline
\end_inset

  $input_file = $ARGV[1]; $output_file = $ARGV[2]; $post_only = 1;
\begin_inset Newline newline
\end_inset

} else {
\begin_inset Newline newline
\end_inset

  &usage unless ($#ARGV == 1);
\begin_inset Newline newline
\end_inset

  $input_file = $ARGV[0]; $output_file = $ARGV[1];
\begin_inset Newline newline
\end_inset

  $pre_only = 0; $post_only = 0;
\begin_inset Newline newline
\end_inset

}
\begin_inset Newline newline
\end_inset

@ %def input_file output_file pre_only post_only
\end_layout

\begin_layout Scrap
<<Subroutines>>=
\begin_inset Newline newline
\end_inset

sub usage() {
\begin_inset Newline newline
\end_inset

  print "Usage: noweb2lyx [-pre | -post] input-file output-file
\begin_inset Newline newline
\end_inset


\begin_inset Newline newline
\end_inset

If -pre is specified, only pre-processes the input-file for reLyX.
\begin_inset Newline newline
\end_inset

Similarly, in the case of -post, post-processes reLyX output.
\begin_inset Newline newline
\end_inset

In case of bugs, Email Kayvan Sylvan <kayvan
\backslash
@sylvan.com>.
\backslash
n";
\begin_inset Newline newline
\end_inset

  exit;
\begin_inset Newline newline
\end_inset

}
\begin_inset Newline newline
\end_inset

@ %def usage
\end_layout

\begin_layout Section
Generating the 
\noun on
noweb2lyx
\noun default
 script
\end_layout

\begin_layout Standard
The noweb2lyx script can be tangled from LyX if you set 
\family typewriter

\backslash
build_command
\family default
 to call a generic script that always extracts a scrap named 
\family typewriter
build-script
\family default
 and executes it.
 Here is an example of such a script:
\end_layout

\begin_layout LyX-Code
#!/bin/sh
\begin_inset Newline newline
\end_inset

notangle -Rbuild-script $1 | sh
\end_layout

\begin_layout Scrap
<<build-script>>=
\begin_inset Newline newline
\end_inset

PREFIX=/usr
\begin_inset Newline newline
\end_inset

notangle -Rnoweb2lyx.in noweb2lyx.nw > noweb2lyx.in
\begin_inset Newline newline
\end_inset

sed -e "s=@PERL@=$PREFIX/bin/perl=" noweb2lyx.in > noweb2lyx
\begin_inset Newline newline
\end_inset

chmod +x noweb2lyx
\begin_inset Newline newline
\end_inset

@
\end_layout

\begin_layout Standard
\begin_inset Newpage newpage
\end_inset


\end_layout

\begin_layout Section*
Macros
\end_layout

\begin_layout Standard

\family roman
\series medium
\shape up
\size normal
\emph off
\bar no
\noun off
\color none
\begin_inset ERT
status collapsed

\begin_layout Plain Layout


\backslash
nowebchunks
\end_layout

\end_inset


\end_layout

\begin_layout Section*
Identifiers
\end_layout

\begin_layout Standard

\family roman
\series medium
\shape up
\size normal
\emph off
\bar no
\noun off
\color none
\begin_inset ERT
status collapsed

\begin_layout Plain Layout


\backslash
nowebindex
\end_layout

\end_inset


\end_layout

\end_body
\end_document
