\floatstyle{ruled}
\newfloat{Prog}{thp}{lop}
\floatname{Prog}{Listing}

\newenvironment{program}
{
  \begin{Prog}
    \renewcommand{\baselinestretch}{1.0}
    \vspace{0.1cm}
}
{
  \end{Prog}
}

\newcounter{tmp}
\newcommand{\CompareWithSize}[4] {
  \begin{Prog}
    \setcounter{tmp}{\theProg}
    \addtocounter{tmp}{1}
    \renewcommand{\baselinestretch}{1.0}    
    \centering
    \begin{tabular}{l||l}
      \begin{minipage}{#3}
        \vspace{0.1cm}
        \UseVerbatim{Side1}
      \end{minipage}
      &
      \begin{minipage}{#4}
        \vspace{0.1cm}
        \UseVerbatim{Side2}
      \end{minipage}
      \\
      {\small \hfill \thetmp.1} & {\small \hfill \thetmp.2}
    \end{tabular}
    \caption{#1}
    \label{#2}
  \end{Prog} 
}

\newcommand{\compare}[2]{\CompareWithSize{#1}{#2}{6.6cm}{6.6cm}}

% use \compare to compare two listings side-by-side; follow an
% example of use; note that the two listings need to be saved as Side1
% and Side2

%\begin{SaveVerbatim}{Side1}
%  for i in range(10):
%    print i
%\end{SaveVerbatim}

%\begin{SaveVerbatim}{Side2}
%  import sys
%  print sys.path
%\end{SaveVerbatim}
%\compare{caption}{label}