Read integers from external data file to document programming code in LaTeX

Question

I am attempting to document my MATLAB programming code in LaTeX. For this, I use the mcode package, which defines the MATLAB lstlisting environment. With the commands

\newcommand{\mfileMain}{main.m}
\newcommand{\mfileMainFirstNumber}{\mfileMainFirstLine}
\newcommand{\mfileMainFirstLine}{26}
\newcommand{\mfileMainLastLine}{33}
\lstinputlisting[firstnumber=\mfileMainFirstNumber,
                 firstline=\mfileMainFirstLine,
                 lastline=\mfileMainLastLine]{\mfileMain}

I set the firstnumber, firstline and lastline parameters and use them to import a piece of MATLAB code into the LaTeX document with \lstinputlisting. However, when I add some code before the \mfileMainFirstLine, in this case 26, the code is shifted and the documentation is ruined. To fix this, I would have to update the line numbers.

I am trying to fix this issue by adding 'tracers' to my MATLAB program. I use the commands

filename=['lstinputlisting_line_numbers_' mfilename '.txt'];
fileID=fopen(filename,'w');

to create a text file in which I store the line numbers for which the code is documented using the command

dbstack_eval=dbstack;fprintf(fileID,[num2str(dbstack_eval.line+1) '\n']);

. This results in a text file lstinputlisting_line_numbers_.txt with content for instance like

53
62
75
91

in case I want to document four parts of the MATLAB program main.m.

What I want to do from here is simply use this line number data in the \lstinputlisting commands. Perhaps it is possible to store the line numbers in the \newcommands{}{}, or perhaps there is a better, more elegant way of doing it. In this way, the line numbers would update automatically in case I add new lines of code. Consequently, my LaTeX document would still be okay, saving me a lot of time not having to update the line numbers myself.

A minimum working example could look like the following. The LaTeX file main.tex would have the content

\documentclass[a4paper]{article}
\usepackage[framed,numbered]{mcode}

% Data for the 'lstinputlisting' environments.
\newcommand{\mfileMain}{main.m}
\newcommand{\mfileMainFirstNumberA}{\mfileMainFirstLineA}
\newcommand{\mfileMainFirstLineA}{WHAT SHOULD I PUT HERE?}
\newcommand{\mfileMainLastLineA}{WHAT SHOULD I PUT HERE?}
\newcommand{\mfileMainFirstNumberB}{\mfileMainFirstLineB}
\newcommand{\mfileMainFirstLineB}{WHAT SHOULD I PUT HERE?}
\newcommand{\mfileMainLastLineB}{WHAT SHOULD I PUT HERE?}

\begin{document}
    In the code
    \lstinputlisting[firstnumber=\mfileMainFirstNumberA,
                     firstline=\mfileMainFirstLineA,
                     lastline=\mfileMainLastLineA]{\mfileMain}
    we calculate the .... 

    And in the code
    \lstinputlisting[firstnumber=\mfileMainFirstNumberB,
                     firstline=\mfileMainFirstLineB,
                     lastline=\mfileMainLastLineB]{\mfileMain}
    we calculate the.....
\end{document}

. The MATLAB file main.m would have the content

%% Line number output.

filename=['lstinputlisting_line_numbers_' mfilename '.txt'];
fileID=fopen(filename,'w');

dbstack_eval=dbstack;fprintf(fileID,[num2str(dbstack_eval.line+1) '\n']);    
%% Input to be specified by user.

alpha=10; % PDE parameter.
x_s=0; % Starting coordinate.
x_e=1; % End coordinate.
N_n=1e2+1; % (N)umber of (n)odes.
N_ip=2; % (N)umber of (i)ntegration (p)oints.

dbstack_eval=dbstack;fprintf(fileID,[num2str(dbstack_eval.line+1) '\n']);    
fclose(fileID); % Close the file 'fileID'.

Answer 1

In my opinion, it would be simpler and more robust to just use linerange markers for listings in comments of your m-file. See the example below. I used the matlab-prettifier package instead of mcode, but the approach should work with either.

Basically, you define a prefix for those linerange markers with the rangeprefix key; here, the prefix I use is simply a percent character (%) followed by a space character:

rangeprefix=\%\ ,

Note that both of those characters must be escaped here (but not in your MATLAB code). Then, in your code, you use a pair of descriptive strings to mark the start and end of each of the ranges of interest. In the example below, I used param and endparam for the first range of interest, and param2 and endparam2 for the second range of interest. Make sure to use

includerangemarker=false

if you don't want the markers themselves to appear in the output.

You can find more details about those linerange markers in subsection 5.7 of the listings manual.

\documentclass{article}

\usepackage[T1]{fontenc}
\usepackage{matlab-prettifier}

\usepackage{filecontents}
\begin{filecontents*}{sample.m}
foo=3
bar=5
baz=foo
foo=bar
bar=baz
% param
% first set of parameters
alpha=10; % PDE parameter.
x_s=0; % Starting coordinate.
x_e=1; % End coordinate.
N_n=1e2+1; % (N)umber of (n)odes.
N_ip=2; % (N)umber of (i)ntegration (p)oints.
% endparam
clear baz
% param2
% second set of parameters
beta=20;
N = 42;
% endparam2
\end{filecontents*}

\lstset{
  style              = Matlab-editor,
  basicstyle         = \mlttfamily,
  rangeprefix        = \%\ ,
  includerangemarker = false,
}

\begin{document}
\lstinputlisting[linerange=param-endparam]{sample.m}
\lstinputlisting[linerange=param2-endparam2]{sample.m}
\end{document}

Answer 2

I am not sure, what the 4th number is expected to be, but this reads the numbers and assigns them to macros.

Apart from this all, one should consider Jubob's comments ;-)

\documentclass[paper=a4,12pt]{scrbook}

\usepackage{etoolbox}%
\usepackage{blindtext}%
\usepackage[framed,numbered]{mcode}%

\newread\mylinenumbers

\newcommand{\mfileMain}{main.m}%

\def\mFileMainFirstLine{}
\def\mFileMainFirstNumber{}
\def\mFileMainLastLine{}


\AtBeginDocument{%
  \openin\mylinenumbers=lstinputlisting_line_numbers_.tex
  \read\mylinenumbers to \mFileMainFirstNumber
  \read\mylinenumbers to \mFileMainFirstLine
  \read\mylinenumbers to \mFileMainLastLine
  \closein\mylinenumbers
}%




\begin{document}

\lstinputlisting[firstnumber=\mFileMainFirstNumber,
                     firstline=\mFileMainFirstLine,
                     lastline=\mFileMainLastLine]{\mfileMain}

\end{document}

Improved version

Use a separate command \ReadinLineNumbers just before the \lstinputlisting takes places, therefore updating the linenumber information.

In principle, this could be added to the \lstinputlisting` command directly, it would break for other calls of the command however.

\documentclass[paper=a4,12pt]{scrbook}
\usepackage[framed,numbered]{mcode}%

\newread\mylinenumbers

\newcommand{\mfileMain}{main.m}%

\def\mFileMainFirstLine{}
\def\mFileMainFirstNumber{}
\def\mFileMainLastLine{}

% This command assumes that there always triples for the line number information
\newcommand{\ReadinLineNumbers}{%
  \read\mylinenumbers to \mFileMainFirstNumber
  \read\mylinenumbers to \mFileMainFirstLine
  \read\mylinenumbers to \mFileMainLastLine
}%

\AtBeginDocument{%
  \openin\mylinenumbers=lstinputlisting_line_numbers_.tex
}%

\AtEndDocument{%
  \closein\mylinenumbers
}%

\begin{document}

\ReadinLineNumbers

\lstinputlisting[firstnumber=\mFileMainFirstNumber,
                     firstline=\mFileMainFirstLine,
                     lastline=\mFileMainLastLine]{\mfileMain}

\ReadinLineNumbers

\lstinputlisting[firstnumber=\mFileMainFirstNumber,
                     firstline=\mFileMainFirstLine,
                     lastline=\mFileMainLastLine]{\mfileMain}

\end{document}