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List:       lyx-users
Subject:    alternate code scrap definition
From:       "Sam Liddicott" <sam () liddicott ! com>
Date:       2009-07-28 14:17:29
Message-ID: 4A6F0879.8050808 () liddicott ! com
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This is a long post, but quite exciting to anyone who uses or wants to
improve literate programming with Lyx.

Along with using a literate module instead of a literate class
(attached), I've got a suggestion for an alternate code scrap definition.

Instead of using LatexType Paragraph with LabelType Static, (which
requires literal <<label>>= and @) I suggest these changes:

LatexType Environment
LatextName CodeScrap
LabelType Manual

It means that the first line which normally contains:
<<scrap-name>>=

will be the environment's label, shown in a different colour and we can
do without the << >>= because it will still have semantic meaning with
Lyx as the label.

So far, the Latex would come out like this:

\begin{CodeScrap}
[{scrap-name}]
int x=2;
int y=3;
\end{CodeScrap}

Which is not right, but some sed can turn:
  \begin{CodeScrap}\n[{scrap-name}]
into
  \n<<scrap-name>>=
and turn
  \end{CodeScrap}
into
  @

before we pass to notangle or noweave.

Such sed is:

sed -e '/\\begin{xdummy}/{s/^.*//;n;
        s/^\[{/<</;s/}\] *$/>>=/;};/\\end{xdummy}/s/^.*/@\n/'

Further-more, we can use optional non-label text on the same line as the
label to contain a cross-reference definition such as would be used by:
  \nextchunklabel{LABEL-NAME}

This means that to add a cross-reference label to a code chunk you would:
1. select "Scrap" from the drop-down
2. type in the scrap name
3. press space
3a. press space again and type the xref label
4. press ctrl enter and start typeing code.

just miss out step 3a if you don't want a cross-reference label.

This sed will do all of that (makes use of the hold space to detect the
CodeScrap environment):

sed -e '/\\begin{CodeScrap}/{h;s/^.*//};/\\end{CodeScrap}/s/^.*/@\n/;
/^\[{/{
  x;/\\begin{CodeScrap}/{x
  s/^\[{/<</;
  s/^\(.* *}\]\) *\([^ ].*\)/\\nextchunklabel{\2}\n\1/
  s/ *}\] */>>=/
  x}
  x
}'

It converted this Lyx (CodeScrap environment):
--8<-----8<-----8<-----8<-----8<---
something() start-of-something
  int something() {
    int x=2;
    int y=3;
  }

something_else
  #warning I'm bored
--8<-----8<-----8<-----8<-----8<---

into this latex

--8<-----8<-----8<-----8<-----8<---

\nextchunklabel{start-of-something}
<<something()>>=
int something() {
  int x=2;
  int y=3;
}

<<something_else>>=
#warning I'm bored
@
--8<-----8<-----8<-----8<-----8<---

Which is spot on!

I wish that a module file could define the conversion filter. The
attached module file says:

OutputType literate

it would be good if there was also:

OutputFilter: sed -e ....

which defines a filter which is used to produce the specified output type.

Sam

["literate.module" (text/plain)]

#\DeclareLyXModule[noweb.sty]{Noweb}
#DescriptionBegin
#Adds \usepackage{noweb} to your document, along with the Scrap style.
#Also fixes the CharStyle:Code to work with noweb, redefining nowebs
#\code command to \nwcode (if you need it).
#DescriptionEnd

#use this filter on the output before passing to notangle or noweave:
# sed -e '/\\begin{CodeScrap}/{h;s/^.*//};/\\end{CodeScrap}/s/^.*/@\n/;/^\[{/{x;/\\begin{CodeScrap}/{x;s/^\[{/<</;s/^\(.* \
*}\]\) *\([^ ].*\)/\\nextchunklabel{\2}\n\1/;s/ *}\] */>>=/;x};x}'

Format 11
OutputType              literate

AddToPreamble
	\usepackage{noweb}
	% noweb breaks code command
	\newcommand{\nwcode}{\code}
	\renewcommand{\code}[1]{\texttt{#1}}
EndPreamble


Style Scrap
        Margin                First_Dynamic
        LatexType             Environment
        LatexName             CodeScrap
        NewLine               0
        LeftMargin            MMM
        ParSep                0.4
        TopSep                0.4
        BottomSep             0.4
        ItemSep               0.4
        Align                 Left
        AlignPossible         Block,Left
        FreeSpacing           1
        PassThru              1
        LabelType             Manual
        LabelFont
          Color               magenta
        EndFont
        TextFont
          Color               latex
          Family              Typewriter
        EndFont
End



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