Update documentation

[lyx.git] / lib / examples / Modules / Noweb2LyX.lyx

#LyX 2.4 created this file. For more info see https://www.lyx.org/
\lyxformat 600
\begin_document
\begin_header
\save_transient_properties true
\origin /systemlyxdir/examples/Modules/
\textclass 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
\use_default_options false
\begin_modules
noweb
\end_modules
\maintain_unincluded_children no
\language english
\language_package default
\inputencoding utf8
\fontencoding auto
\font_roman "lmodern" "default"
\font_sans "default" "default"
\font_typewriter "default" "default"
\font_math "auto" "auto"
\font_default_family default
\use_non_tex_fonts false
\font_sc false
\font_sans_osf false
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\font_sf_scale 100 100
\font_tt_scale 100 100
\use_microtype false
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\graphics default
\default_output_format default
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\bibtex_command default
\index_command default
\paperfontsize default
\spacing single
\use_hyperref false
\papersize default
\use_geometry false
\use_package amsmath 1
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\use_package cancel 1
\use_package esint 1
\use_package mathdots 1
\use_package mathtools 1
\use_package mhchem 1
\use_package stackrel 1
\use_package stmaryrd 1
\use_package undertilde 1
\cite_engine basic
\cite_engine_type default
\biblio_style plain
\use_bibtopic false
\use_indices false
\paperorientation portrait
\suppress_date false
\justification true
\use_refstyle 0
\use_minted 0
\use_lineno 0
\index Index
\shortcut idx
\color #008000
\end_index
\secnumdepth 3
\tocdepth 3
\paragraph_separation indent
\paragraph_indentation default
\is_math_indent 0
\math_numbering_side default
\quotes_style english
\dynamic_quotes 0
\papercolumns 1
\papersides 1
\paperpagestyle default
\tracking_changes false
\postpone_fragile_content false
\output_changes false
\html_math_output 0
\html_css_as_file 0
\html_be_strict false
\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 \SpecialChar 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, \SpecialChar LyX
 now supports Literate Programming using 
\noun on
noweb
\noun default
.
 This addition to \SpecialChar 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 \SpecialChar 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 \SpecialChar LyX
.
\end_layout

\begin_layout Standard
\begin_inset Flex Chunk
status open

\begin_layout Plain Layout

\begin_inset Argument 1
status open

\begin_layout Plain Layout

noweb2lyx.in
\end_layout

\end_inset

#!@PERL@
\end_layout

\begin_layout Plain Layout

# 
\end_layout

\begin_layout Plain Layout

# Copyright (C) 1999 Kayvan A.
 Sylvan <kayvan@sylvan.com>
\end_layout

\begin_layout Plain Layout

# You are free to use and modify this code under the terms of
\end_layout

\begin_layout Plain Layout

# the GNU General Public Licence version 2 or later.
\end_layout

\begin_layout Plain Layout

#
\end_layout

\begin_layout Plain Layout

# Written with assistance from:
\end_layout

\begin_layout Plain Layout

#   Edmar Wienskoski Jr.
 <edmar-w-jr@technologist.com>
\end_layout

\begin_layout Plain Layout

#   Amir Karger <karger@post.harvard.edu>
\end_layout

\begin_layout Plain Layout

#
\end_layout

\begin_layout Plain Layout

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

\begin_layout Plain Layout

#
\end_layout

\begin_layout Plain Layout

# NOTE: This file was automatically generated from noweb2lyx.lyx using noweb.
\end_layout

\begin_layout Plain Layout

#
\end_layout

\begin_layout Plain Layout

<<Setup variables from user supplied args>>
\end_layout

\begin_layout Plain Layout

<<Subroutines>>
\end_layout

\begin_layout Plain Layout

<<Convert noweb to LyX>>
\end_layout

\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.
\end_layout

\begin_layout Standard
\begin_inset ERT
status open

\begin_layout Plain Layout

We can do arbitrary LaTeX code here.
\end_layout

\begin_layout Plain Layout

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

\end_inset


\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 \SpecialChar LyX
 team that
 knew about the literate programming extensions and re\SpecialChar LyX
 (the \SpecialChar LaTeX
 importing code).
\end_layout

\begin_layout Standard
One of the first ideas was to extend the re\SpecialChar LyX
 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 re\SpecialChar LyX
 contains a very useful literal
 quoting mechanism.
 If the input file contains the construct
\end_layout

\begin_layout LyX-Code

\backslash
begin{re\SpecialChar LyX
skip}
\begin_inset Newline newline
\end_inset

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


\backslash
end{re\SpecialChar LyX
skip}
\end_layout

\begin_layout Standard
then re\SpecialChar LyX
 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{re\SpecialChar LyX
skip}
\family default
 and 
\family typewriter

\backslash
end{re\SpecialChar LyX
skip}
\family default
.
\end_layout

\begin_layout Standard
Once re\SpecialChar LyX
 is done with the input file, the problem is reduced to changing
 the code chunks from \SpecialChar LyX
's \SpecialChar LaTeX
 layout to the Chunk 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 re\SpecialChar LyX
.
 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 Standard
\begin_inset Flex Chunk
status open

\begin_layout Plain Layout

\begin_inset Argument 1
status open

\begin_layout Plain Layout

Convert noweb to \SpecialChar LyX

\end_layout

\end_inset

if (!$post_only) {
\end_layout

\begin_layout Plain Layout

  <<Transform noweb for reLyX>>
\end_layout

\begin_layout Plain Layout

}
\end_layout

\begin_layout Plain Layout

if ((!$pre_only) && (!$post_only)) {
\end_layout

\begin_layout Plain Layout

  <<Run reLyX on intermediate file>>
\end_layout

\begin_layout Plain Layout

}
\end_layout

\begin_layout Plain Layout

if (!$pre_only) {
\end_layout

\begin_layout Plain Layout

  <<Fix up LyX file>>
\end_layout

\begin_layout Plain Layout

}
\end_layout

\begin_layout Plain Layout

<<Clean up>>
\end_layout

\end_inset


\end_layout

\begin_layout Section
Making a file that re\SpecialChar LyX
 can process
\end_layout

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

\begin_layout Standard
\begin_inset Flex Chunk
status open

\begin_layout Plain Layout

\end_layout

\begin_layout Plain Layout

<<Transform noweb for reLyX>>=
\end_layout

\begin_layout Plain Layout

<<Setup INPUT and OUTPUT>>
\end_layout

\begin_layout Plain Layout

inputline: while(<INPUT>)
\end_layout

\begin_layout Plain Layout

{
\end_layout

\begin_layout Plain Layout

  if (/^
\backslash
s*
\backslash
<
\backslash
<.*
\backslash
>
\backslash
>=/) { # Beginning of a noweb chunk
\end_layout

\begin_layout Plain Layout

    <<Read in and output the noweb code chunk>>
\end_layout

\begin_layout Plain Layout

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

\begin_layout Plain Layout

    print OUTPUT $1; # We do not need the ``@'' part
\end_layout

\begin_layout Plain Layout

  } elsif (/
\backslash
[
\backslash
[.+
\backslash
]
\backslash
]/) { # noweb quoted code
\end_layout

\begin_layout Plain Layout

    <<Perform special input quoting of [[var]]>>
\end_layout

\begin_layout Plain Layout

  } else {
\end_layout

\begin_layout Plain Layout

    print OUTPUT; # Just let the line pass through
\end_layout

\begin_layout Plain Layout

  }
\end_layout

\begin_layout Plain Layout

}
\end_layout

\begin_layout Plain Layout

<<Close INPUT and OUTPUT>>
\end_layout

\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 re\SpecialChar LyX
 confusing lists composed of ``[[...]]''
 constructs.
\end_layout

\begin_layout Standard
\begin_inset ERT
status open

\begin_layout Plain Layout

<<Perform special input quoting of [[var]]>>=
\end_layout

\begin_layout Plain Layout

s/
\backslash
[
\backslash
[.+?
\backslash
]{2,}/{$&}/g;
\end_layout

\begin_layout Plain Layout

print OUTPUT;
\end_layout

\begin_layout Plain Layout

@
\end_layout

\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 re\SpecialChar LyX
.
\end_layout

\begin_layout Standard
\begin_inset Flex Chunk
status open

\begin_layout Plain Layout

\begin_inset Argument 1
status open

\begin_layout Plain Layout

Read in and output the noweb code chunk
\end_layout

\end_inset

<<Save the beginning of the chunk to savedchunk>>
\end_layout

\begin_layout Plain Layout

<<Concatenate the rest of the chunk>>
\end_layout

\begin_layout Plain Layout

<<print out the chunk in a reLyXskip block>>
\end_layout

\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 re\SpecialChar LyX
.
 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 Standard
\begin_inset Flex Chunk
status open

\begin_layout Plain Layout

\begin_inset Argument 1
status open

\begin_layout Plain Layout

Setup INPUT and OUTPUT
\end_layout

\end_inset

if ($pre_only) {
\end_layout

\begin_layout Plain Layout

  &setup_files($input_file, $output_file);
\end_layout

\begin_layout Plain Layout

} else {
\end_layout

\begin_layout Plain Layout

  $relyx_file = "temp$$";
\end_layout

\begin_layout Plain Layout

  &setup_files($input_file, $relyx_file);
\end_layout

\begin_layout Plain Layout

}
\end_layout

\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 Standard
\begin_inset ERT
status open

\begin_layout Plain Layout

<<Subroutines>>=
\end_layout

\begin_layout Plain Layout

sub setup_files {
\end_layout

\begin_layout Plain Layout

  my($in, $out) = @_;
\end_layout

\begin_layout Plain Layout

  open(INPUT, "<$in") || die "Cannot read $in: $!
\backslash
n";
\end_layout

\begin_layout Plain Layout

  open(OUTPUT, ">$out") || die "Cannot write $out: $!
\backslash
n";
\end_layout

\begin_layout Plain Layout

}
\end_layout

\begin_layout Plain Layout

@ %def setup_files
\end_layout

\end_inset


\end_layout

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

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

\begin_layout Standard
\begin_inset Flex Chunk
status open

\begin_layout Plain Layout

\begin_inset Argument 1
status open

\begin_layout Plain Layout

Save the beginning of the chunk to savedchunk
\end_layout

\end_inset

$savedchunk = $_;
\end_layout

\begin_layout Plain Layout

$endLine = "";
\end_layout

\end_inset


\end_layout

\begin_layout Standard
\begin_inset ERT
status open

\begin_layout Plain Layout

<<Concatenate the rest of the chunk>>=
\end_layout

\begin_layout Plain Layout

chunkline: while (<INPUT>) {
\end_layout

\begin_layout Plain Layout

 last chunkline if /^@
\backslash
s+/;
\end_layout

\begin_layout Plain Layout

 $savedchunk .= $_;
\end_layout

\begin_layout Plain Layout

};
\end_layout

\begin_layout Plain Layout

switch: {
\end_layout

\begin_layout Plain Layout

 if (/^@
\backslash
s+$/) {$savedchunk .= $_; last switch; }
\end_layout

\begin_layout Plain Layout

 if (/^@
\backslash
s+%def.*$/) {$savedchunk .= $_; last switch; }
\end_layout

\begin_layout Plain Layout

 if (/^@
\backslash
s+(.*)$/) {$savedchunk .= "@
\backslash
n"; $endLine = "$1
\backslash
n"; }
\end_layout

\begin_layout Plain Layout

}
\end_layout

\begin_layout Plain Layout

@
\end_layout

\end_inset


\end_layout

\begin_layout Subsection
Printing out the chunk
\end_layout

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

\begin_layout Standard
\begin_inset Flex Chunk
status open

\begin_layout Plain Layout

\begin_inset Argument 1
status open

\begin_layout Plain Layout

print out the chunk in a re\SpecialChar LyX
skip block
\end_layout

\end_inset

print OUTPUT "
\backslash

\backslash
begin{reLyXskip}
\backslash
n";
\end_layout

\begin_layout Plain Layout

print OUTPUT $savedchunk;
\end_layout

\begin_layout Plain Layout

print OUTPUT "
\backslash

\backslash
end{reLyXskip}
\backslash
n
\backslash
n";
\end_layout

\begin_layout Plain Layout

print OUTPUT "$endLine";
\end_layout

\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 Standard
\begin_inset Flex Chunk
status open

\begin_layout Plain Layout

\begin_inset Argument 1
status open

\begin_layout Plain Layout

Close INPUT and OUTPUT
\end_layout

\end_inset

close(INPUT);
\end_layout

\begin_layout Plain Layout

close(OUTPUT);
\end_layout

\end_inset


\end_layout

\begin_layout Section
Running re\SpecialChar LyX

\end_layout

\begin_layout Standard
In this section, we describe and implement the code that runs re\SpecialChar LyX
 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 re\SpecialChar LyX
, 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 Standard
\begin_inset Flex Chunk
status open

\begin_layout Plain Layout

\begin_inset Argument 1
status open

\begin_layout Plain Layout

Run re\SpecialChar LyX
 on intermediate file
\end_layout

\end_inset

<<Parse for document class>>
\end_layout

\begin_layout Plain Layout

<<Run reLyX with document class>>
\end_layout

\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 \SpecialChar LyX

\begin_inset Foot
status collapsed

\begin_layout Plain Layout
re\SpecialChar LyX
 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 \SpecialChar LyX
 file.
\end_layout

\begin_layout Standard
\begin_inset Flex Chunk
status open

\begin_layout Plain Layout

\begin_inset Argument 1
status open

\begin_layout Plain Layout

Parse for document class
\end_layout

\end_inset

open(INPUT, "<$relyx_file") ||
\end_layout

\begin_layout Plain Layout

  die "Cannot read $relyx_file: $!
\backslash
n";
\end_layout

\begin_layout Plain Layout

$class = "article"; # default if none found
\end_layout

\begin_layout Plain Layout

parse: while(<INPUT>) {
\end_layout

\begin_layout Plain Layout

  if (/
\backslash

\backslash
docu[m]entclass{(.*)}/) {
\end_layout

\begin_layout Plain Layout

    $class = $1;
\end_layout

\begin_layout Plain Layout

    last parse;
\end_layout

\begin_layout Plain Layout

  }
\end_layout

\begin_layout Plain Layout

}
\end_layout

\begin_layout Plain Layout

close(INPUT);
\end_layout

\end_inset


\end_layout

\begin_layout Subsection
Running re\SpecialChar LyX
 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 Standard
\begin_inset ERT
status open

\begin_layout Plain Layout

<<Run reLyX with document class>>= 
\end_layout

\begin_layout Plain Layout

$doc_class = "literate-" .
 $class;
\end_layout

\begin_layout Plain Layout

die "reLyX returned non-zero: $!
\backslash
n"
\end_layout

\begin_layout Plain Layout

  if (system("reLyX -c $doc_class $relyx_file"));
\end_layout

\begin_layout Plain Layout

@
\end_layout

\end_inset


\end_layout

\begin_layout Standard
re\SpecialChar LyX
 performs the main bulk of the translation work.
 Note that if the ``literate-
\emph on
class
\emph default
'' document layout is not found, then re\SpecialChar LyX
 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 re\SpecialChar LyX
 output
\end_layout

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

\begin_layout Standard
\begin_inset Flex Chunk
status open

\begin_layout Plain Layout

\begin_inset Argument 1
status open

\begin_layout Plain Layout

Fix up \SpecialChar LyX
 file
\end_layout

\end_inset

<<Setup INPUT and OUTPUT for the final output>>
\end_layout

\begin_layout Plain Layout

line: while(<INPUT>)
\end_layout

\begin_layout Plain Layout

{
\end_layout

\begin_layout Plain Layout

  <<Fix code chunks in latex layout>>
\end_layout

\begin_layout Plain Layout

  <<Fix [[var]] noweb construct>>
\end_layout

\begin_layout Plain Layout

  print OUTPUT; # default
\end_layout

\begin_layout Plain Layout

} 
\end_layout

\begin_layout Plain Layout

<<Close INPUT and OUTPUT>>
\end_layout

\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
 re\SpecialChar LyX
 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 Standard
\begin_inset Flex Chunk
status open

\begin_layout Plain Layout

\begin_inset Argument 1
status open

\begin_layout Plain Layout

Setup INPUT and OUTPUT for the final output
\end_layout

\end_inset

if ($post_only) {
\end_layout

\begin_layout Plain Layout

  &setup_files("$input_file", "$output_file");
\end_layout

\begin_layout Plain Layout

} else {
\end_layout

\begin_layout Plain Layout

  &setup_files("$relyx_file.lyx", "$output_file");
\end_layout

\begin_layout Plain Layout

}
\end_layout

\end_inset


\end_layout

\begin_layout Subsection
Making sure the code chunks are in the Chunk 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 \SpecialChar LaTeX
 layout by \SpecialChar LyX
 into the Chunk layout.
\end_layout

\begin_layout Standard
\begin_inset Flex Chunk
status open

\begin_layout Plain Layout

\begin_inset Argument 1
status open

\begin_layout Plain Layout

Fix code chunks in latex layout
\end_layout

\end_inset

if (/
\backslash

\backslash
latex latex/) { # Beginning of some latex code
\end_layout

\begin_layout Plain Layout

  if (($line = <INPUT>) =~ /^
\backslash
s*<</) { # code chunk
\end_layout

\begin_layout Plain Layout

    <<Transform this chunk into layout chunk>>
\end_layout

\begin_layout Plain Layout

  } else {
\end_layout

\begin_layout Plain Layout

    # print the 
\backslash
latex latex line + next line
\end_layout

\begin_layout Plain Layout

    print OUTPUT "$_$line";
\end_layout

\begin_layout Plain Layout

  }
\end_layout

\begin_layout Plain Layout

  next line;
\end_layout

\begin_layout Plain Layout

}
\end_layout

\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 chunk layout for it:
\end_layout

\begin_layout Standard
\begin_inset ERT
status open

\begin_layout Plain Layout

<<Transform this chunk into layout chunk>>=
\end_layout

\begin_layout Plain Layout

\end_layout

\begin_layout Plain Layout

$savedchunk = "
\backslash

\backslash
layout Chunk
\backslash
n
\backslash
n$line";
\end_layout

\begin_layout Plain Layout

codeline: while (<INPUT>) {
\end_layout

\begin_layout Plain Layout

 $savedchunk .= $_;
\end_layout

\begin_layout Plain Layout

 last codeline if /^@
\backslash
s+/;
\end_layout

\begin_layout Plain Layout

};
\end_layout

\begin_layout Plain Layout

print OUTPUT $savedchunk;
\end_layout

\begin_layout Plain Layout

<<Slurp up to the end of the latex layout>>
\end_layout

\begin_layout Plain Layout

@
\end_layout

\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 Standard
\begin_inset Flex Chunk
status open

\begin_layout Plain Layout

\begin_inset Argument 1
status open

\begin_layout Plain Layout

Slurp up to the end of the latex layout
\end_layout

\end_inset

slurp: while (<INPUT>) {
\end_layout

\begin_layout Plain Layout

  last slurp if /
\backslash

\backslash
latex /;
\end_layout

\begin_layout Plain Layout

  next slurp if /
\backslash

\backslash
newline/;
\end_layout

\begin_layout Plain Layout

  next slurp if /^
\backslash
s*$/;
\end_layout

\begin_layout Plain Layout

  warn "confused by line: $_";
\end_layout

\begin_layout Plain Layout

}
\end_layout

\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 \SpecialChar LaTeX
 layout in the \SpecialChar LyX
 file.
 Otherwise, \SpecialChar 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 \SpecialChar LaTeX
 code.
\end_layout

\begin_layout Standard
\begin_inset Flex Chunk
status open

\begin_layout Plain Layout

\begin_inset Argument 1
status open

\begin_layout Plain Layout

Fix [[var]] noweb construct
\end_layout

\end_inset

if (/
\backslash
[
\backslash
[.+
\backslash
]
\backslash
]/) { # special code for [[var]]
\end_layout

\begin_layout Plain Layout

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

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

\backslash
latex default
\backslash
n/g;
\end_layout

\begin_layout Plain Layout

  print OUTPUT;
\end_layout

\begin_layout Plain Layout

  next line;
\end_layout

\begin_layout Plain Layout

}
\end_layout

\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 Standard
\begin_inset Flex Chunk
status open

\begin_layout Plain Layout

\begin_inset Argument 1
status open

\begin_layout Plain Layout

Clean up
\end_layout

\end_inset

system("rm -f $relyx_file*") unless ($post_only || $pre_only);
\end_layout

\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 re\SpecialChar LyX
 to pre-process or postprocess
 files in the import pipeline.
\end_layout

\begin_layout Standard
\begin_inset ERT
status open

\begin_layout Plain Layout

<<Setup variables from user supplied args>>=
\end_layout

\begin_layout Plain Layout

&usage() if ($#ARGV < 1); # zero or one argument 
\end_layout

\begin_layout Plain Layout

if ($ARGV[0] eq "-pre") {
\end_layout

\begin_layout Plain Layout

  &usage unless ($#ARGV == 2);
\end_layout

\begin_layout Plain Layout

  $input_file = $ARGV[1]; $output_file = $ARGV[2]; $pre_only = 1;
\end_layout

\begin_layout Plain Layout

} elsif ($ARGV[0] eq "-post") {
\end_layout

\begin_layout Plain Layout

  &usage unless ($#ARGV == 2);
\end_layout

\begin_layout Plain Layout

  $input_file = $ARGV[1]; $output_file = $ARGV[2]; $post_only = 1;
\end_layout

\begin_layout Plain Layout

} else {
\end_layout

\begin_layout Plain Layout

  &usage unless ($#ARGV == 1);
\end_layout

\begin_layout Plain Layout

  $input_file = $ARGV[0]; $output_file = $ARGV[1];
\end_layout

\begin_layout Plain Layout

  $pre_only = 0; $post_only = 0;
\end_layout

\begin_layout Plain Layout

}
\end_layout

\begin_layout Plain Layout

@ %def input_file output_file pre_only post_only
\end_layout

\begin_layout Plain Layout

<<Subroutines>>=
\end_layout

\begin_layout Plain Layout

sub usage() {
\end_layout

\begin_layout Plain Layout

  print "Usage: noweb2lyx [-pre | -post] input-file output-file
\end_layout

\begin_layout Plain Layout

\end_layout

\begin_layout Plain Layout

If -pre is specified, only pre-processes the input-file for reLyX.
\end_layout

\begin_layout Plain Layout

Similarly, in the case of -post, post-processes reLyX output.
\end_layout

\begin_layout Plain Layout

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

\begin_layout Plain Layout

  exit;
\end_layout

\begin_layout Plain Layout

}
\end_layout

\begin_layout Plain Layout

@ %def usage
\end_layout

\end_inset


\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 \SpecialChar LyX
 if you set 
\family typewriter

\backslash
build_command
\family default
 to call a generic script that always extracts a chunk 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 | env NOWEB_SOURCE=$1 NOWEB_OUTPUT_DIR=$2 sh
\end_layout

\begin_layout Standard
\begin_inset Flex Chunk
status open

\begin_layout Plain Layout

\begin_inset Argument 1
status open

\begin_layout Plain Layout

build-script
\end_layout

\end_inset

PREFIX=/usr
\end_layout

\begin_layout Plain Layout

notangle -Rnoweb2lyx.in noweb2lyx.nw > noweb2lyx.in
\end_layout

\begin_layout Plain Layout

sed -e "s=@PERL@=$PREFIX/bin/perl=" noweb2lyx.in > noweb2lyx
\end_layout

\begin_layout Plain Layout

chmod +x noweb2lyx
\end_layout

\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