Reuse command portion in LaTeX

Question

I defined several new code environments (using listings' lstnewenvironment); they all share the same attributes except one (the language used). For example:

\documentclass[a4paper,12pt]{book}
\usepackage{listings}
\usepackage[usenames,dvipsnames]{xcolor}
\lstnewenvironment{xml}
{
 \lstset
 {
  literate=
  {é}{{\'e}}1
  {É}{{\'E}}1
  {à}{{\`a}}1 {è}{{\`e}}1 {ì}{{\`i}}1 {ò}{{\`o}}1 {ù}{{\`u}}1 {î}{{\^i}}1
  {À}{{\`A}}1 {È}{{\'E}}1 {Ì}{{\`I}}1 {Ò}{{\`O}}1 {Ù}{{\`U}}1 {Î}{{\^I}}1,
  language=XML,
  breaklines=true,
  xleftmargin=\parindent,
  showstringspaces=false,
  showspaces=false,
  showtabs=false,
  keepspaces=true,
  tabsize=2,
  captionpos=t,
  numbers=left,
  numbersep=5pt,
  numberstyle=\tiny\color{graycode},
  escapeinside={(*}{*)},
  basicstyle=\footnotesize\ttfamily,
  keywordstyle=\bfseries\color{green!40!black},
  commentstyle=\itshape\color{purple!40!black},
  identifierstyle=\color{blue},
  stringstyle=\color{orange}
 }
}
{}

\begin{document}
  \begin{xml}
   <something> ... </something>
  \end{xml}
\end{document}

I'd like to refactor my code in a way that I keep the common stuff in some sort of macro that dumps as-is (verbatim) whatever stored in the point where it's called. Something like:

\newcommand{\stringlstset}
{
  literate = ...
  breaklines = ...
  ...
}
\lstnewenvironment{xml}
{
 \lstset
 {
  \stringlstset
  language = xml
  ...
 }
}
\lstnewenvironment{prolog}
{
 \lstset
 {
  \stringlstset
  language = prolog
  ...
 }
}

I gather you have to use some low-level gimmick to get this done. I did some googling around but I couldn't come up with a working solution. ConTeXt's buffers, for example, looked promising, but they can't be used here.

There may be something in listings to deal with this, but I'm interested in a general solution here.

Answer 1

The second argument of \lstnewenvironment is just arbitrary code to execute before the environment. It can therefore consist of several \lstset commands, and you can put your common customisations in to one command, say \stringlstset, that is a \lstset in its own right. Here is a small example:

\documentclass[a4paper,12pt]{book}

\usepackage{listings}
\usepackage[usenames,dvipsnames]{xcolor}

\newcommand{\stringlstset}{\lstset{
    breaklines=true,
    showspaces=false}}

\lstnewenvironment{xml}
{\lstset{language=XML}\stringlstset}
{}

\begin{document}

\begin{xml}
  <something> Somethig long enough to see a breaking of the line </something>
\end{xml}

\begin{lstlisting}
  <something> Somethig long enough to see a breaking of the line </something>
\end{lstlisting}

\end{document}

producing

with line breaks in the xml environment but not in the lstlistng environment.

Answer 2

Instead of

\lstnewenvironment{whatever}
{
 \lstset
 {
  \stringlstset,
  language = whatever,
  ...
 }
}

you can

\lstnewenvironment{whatever}
{
 \expandafter\lstset
 \expandafter{
  \stringlstset,
  language = whatever,
  ...
 }
}