\documentclass[a4paper,10pt]{article}
\usepackage{amsmath}
\usepackage{amssymb}

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Author: Thomas Braun
% begin: Fri 7 april 2006
% last edit: --
% License: GPLv2 or later
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

\input{definitions}

\begin{document}
\mathcommand{\downarrow}
\mathcommand{\Downarrow}
\mathcommand{[}
\mathcommand{]}
\mathcommand{\langle}
\mathcommand{\rangle}
\mathcommand{|}
\mathcommand{\|}
\mathcommand{\lceil}
\mathcommand{\rceil}
\mathcommand{\uparrow}
\mathcommand{\Uparrow}
\mathcommand{\lfloor}
\mathcommand{\rfloor}
\mathcommand{\updownarrow}
\mathcommand{\Updownarrow}
\mathcommand{(}
\mathcommand{)}
\mathcommand{\{}
\mathcommand{\}}
\mathcommand{/}
\mathcommand{\backslash}
\par
\mathcommand[\lmoustache]{\left \lmoustache \right.}
\mathcommand[\rmoustache]{\left \rmoustache \right.}
\mathcommand[\lgroup]{\left \lgroup \right.}
\mathcommand[\rgroup]{\left \rgroup \right.}
\mathcommand[\arrowvert]{\left \arrowvert \right.}
\mathcommand[\Arrowvert]{\left \Arrowvert \right.}
\mathcommand[\bracevert]{\left \bracevert \right.}
\par
\begin{neededpkgs}{amsmath}
\mathcommand{\lvert}
\mathcommand{\rvert}
\mathcommand{\lVert} 
\mathcommand{\rVert}
\end{neededpkgs}
\par
\begin{neededpkgs}{amssymb}
\mathcommand{\ulcorner}
\mathcommand{\urcorner}
\mathcommand{\llcorner}
\mathcommand{\lrcorner}
\end{neededpkgs}

\end{document}