%%% OLD:
\newcommand{\fs}{\left[ \begin{array}{l}}
\newcommand{\fsfs}{\end{array} \right] \vspace{0.5ex}}
\def\ifsfs#1{\end{array} \right]_{#1} \vspace{0.5ex}}
\newcommand{\fmatrix}{\[ \fs}
\newcommand{\lmatrix}{\fsfs \]}
\setlength{\fboxsep}{1pt}
\newcommand{\fb}[1]{{\framebox{\footnotesize#1}}}



%%% NEW:


% assumption: already in mathematical mode..

%%% \avm[Index]{AttValPairs}
%%% first argument is a sequence of attribute value pairs, seperated
%%% by \\
%%% optional second argument is the index, which is subscripted on
%%% right bracket
\long\def\xavm[#1]#2{\left[ \begin{array}{l}#2 %
                \end{array} \right]_{#1} \vspace{0.5ex}}


\def\avm{\@ifnextchar[{\xavm}{\xavm[{}]}}



% constants and variables in \rm
% subscripted variables, attributes, constants: \var[subscript]{Varname}
% attributes in \sc


\def\xvar[#1]#2{\mbox{\rm #2}_{#1}}
\def\var{\@ifnextchar[{\xvar}{\xvar[{}]}}

\def\xatt[#1]#2{\mbox{\it #2}_{#1}}
\def\att{\@ifnextchar[{\xatt}{\xatt[{}]}}

\def\xcon[#1]#2{\mbox{\rm #2}_{#1}}
\def\con{\@ifnextchar[{\xcon}{\xcon[{}]}}