codeshow.sty

% -*- coding: utf-8 -*-

\NeedsTeXFormat{LaTeX2e}
\ProvidesPackage{codeshow}[2014/07/05 v0.0.1 Show code and its result]
\RequirePackage{verbatim,xcolor}

\newbox\savedlines
\newtoks\savedtokens

\def\codeshow{%
  \global\savedtokens={}%
  \def\verbatim@processline{%
    {\setbox0=\hbox{\the\verbatim@line}%
     \hsize=\wd0
     \the\verbatim@line\par}%
    \global\savedtokens=\expandafter{\the\expandafter\savedtokens\the\verbatim@line^^J}}%
  \@tempswatrue
  \setbox0=\vbox\bgroup\parskip=0pt\topsep=0pt\partopsep=0pt
  \verbatim}
\def\endcodeshow{\endverbatim%
  \unskip\setbox0=\lastbox\egroup
  \global\setbox\savedlines=\box0
  \addvspace{1em}\par\noindent%
  \colorbox{lightgray}{%
    \begin{minipage}{.55\textwidth}{\usebox\savedlines}\end{minipage}}%
  \hfill\fbox{\parbox{.40\textwidth}%
    {\scantokens\expandafter{\the\savedtokens\unskip\endinput}}}%
  \par\addvspace{1em}}