\usepackage{listings}

\usepackage{color}

\definecolor{hellgelb}{rgb}{1,1,0.9}

\definecolor{colKeys}{rgb}{0,0,1}

\definecolor{colIdentifier}{rgb}{0,0,0}

\definecolor{colComments}{rgb}{1,0,0}

\definecolor{colString}{rgb}{0,0.5,0}

% Symbol to put when line wraps

\newcommand{\wrapsign}{\hbox{\rm\ensuremath\hookleftarrow}}

%

% Default verbatim layout used if \lstparamset not defined

%

\@ifundefined{lstparamset}{

\lstset{%

    basicstyle=\ttfamily\small, %

    identifierstyle=\color{colIdentifier}, %

    keywordstyle=\color{colKeys}, %

    stringstyle=\color{colString}, %

    commentstyle=\color{colComments}, %

    tabsize=2, %

    frame=single, %

    framerule=0pt, %

    extendedchars=true, %

    showspaces=false, %

    showlines=true, %

    showstringspaces=false, %

    numberstyle=\tiny, %

    breaklines=true, %

    prebreak={\space\wrapsign}, %

    backgroundcolor=\color[gray]{0.95}, %

    breakautoindent=true, %

    captionpos=b%

}

}{

% Call the user macro that defines the layout

\lstparamset

}

%

% GAP language, derivated from Pascal, has more keywords to highlight

%

\lstdefinelanguage[]{GAP}[]{Pascal}{%

    morekeywords={od,fi,alias}%

}

% Lengths to compute the listing width from the number of characters

\newlength{\lstcharwidth}

\newlength{\lstcharwidthb}

\newlength{\lstframesep}

\newlength{\lstwidth}

\setlength{\lstcharwidth}{\lst@width}

%\let\lstcharwidth\lst@width

\setlength{\lstframesep}{\lst@frametextsep}

% Setup to compute a char width

\def\lstsetup{\sbox{\z@}{\lstinline!x!}%

  \settowidth{\lstcharwidth}{\usebox{\z@}}%

  \sbox{\z@}{\lstinline[basicstyle=\ttfamily]!x!}

  \settowidth{\lstcharwidthb}{\usebox{\z@}}}

% Environment to render fancyvrb like listings does

\newenvironment{fvlisting}[1][]

  {\lstset{fancyvrb,#1}}

  {\lstset{fancyvrb=false}}