Redefining environment within a macro

Question

Hel-lo, I am a LaTeX programming newbie.

While formatting my document, I found that it will look nice if I can modify the theorem environment (with amsthm package). So I tried the following code

\makeatletter
\newcount\@envcount
\newcommand{\enclosebox}[2]{%
    % Create copies of old environments
    \expandafter\let\expandafter\@old\csname #1\endcsname%
    \expandafter\let\expandafter\@oldend\csname end#1\endcsname%
    % Redefine environment using old ones.
    \renewenvironment{#1}[1][]{%
        \@nameuse{@old}[##1]%
        \begin{#2}%
    }{%
        \end{#2}%
        \@nameuse{@oldend}%
    }%
}
\makeatother

This command inserts a new environment (with name #2) to the original environment (with name #1). With this, I can modify theorem environments like this:

 \newtheorem{theorem}{Theorem}
 \enclosebox{theorem}{<some box environment>}

The problem is, the token \@old and \@oldend are overwritten whenever I call \enclosebox command. For example,

 \enclosebox{theorem}{shadebox}
 \enclosebox{definition}{shadebox}
 \enclosebox{example}{leftbar}

overwrites my old definition and theorem environment, resulting in something like:

So I tried using \csname ~ \endcsname to assign the name dynamically, but the compiler just spits out a bunch of errors.

Of course I can resolve this problem by pasting multiple copy of the code and modifying each one by hands... but I am doing in this way just to avoid this clumsy solution.

I have no idea how to fix my code. Can you help me?

Answer 1

For a solution with the original framed package, see below

As an ready to use alternative, instead of using framed and doing all the work, I'd suggest you to use \surroundwithmdframed from the mdframed that was designed specifically for this purpose:

\documentclass{article}
\usepackage{xcolor}
\usepackage{amsthm}
\usepackage[framemethod=tikz]{mdframed}
\usepackage{lipsum}

\newtheorem{theorem}{Theorem}
\theoremstyle{definition}
\newtheorem{definition}{Definition}
\theoremstyle{remark}
\newtheorem{example}{Example}

\surroundwithmdframed[hidealllines=true,backgroundcolor=gray!30]{theorem}
\surroundwithmdframed[backgroundcolor=red,backgroundcolor=cyan!30]{definition}
\surroundwithmdframed[backgroundcolor=red,backgroundcolor=orange!30,roundcorner=10pt]{example}

\begin{document}


\begin{theorem}
\lipsum[4]
\end{theorem}

\begin{definition}
\lipsum[4]
\end{definition}

\begin{example}
\lipsum[4]
\end{example}

\end{document}

And here's a possibility using framed and the etoolbox package to easily define your command \enclosebox:

\documentclass{article}
\usepackage{etoolbox}
\usepackage{xcolor}
\usepackage{amsthm}
\usepackage{framed}
\usepackage{lipsum}

\colorlet{shadecolor}{gray!30}

\newcommand\enclosebox[2]{%
  \BeforeBeginEnvironment{#1}{\begin{#2}}%
  \AfterEndEnvironment{#1}{\end{#2}}%
}

\newtheorem{theorem}{Theorem}
\theoremstyle{definition}
\newtheorem{definition}{Definition}
\theoremstyle{remark}
\newtheorem{example}{Example}

\enclosebox{theorem}{framed}
\enclosebox{example}{shaded}
\enclosebox{definition}{leftbar}

\begin{document}

\begin{theorem}
\lipsum[4]
\end{theorem}

\begin{definition}
\lipsum[4]
\end{definition}

\begin{example}
\lipsum[4]
\end{example}

\end{document}