Macro to multicol section content but not section title

Question

\section{Introduction}

I want to write a macro to that makes the above behave the same as:

\usepackage{multicol}
\begin{multicols}{2}[\section{Introduction}]

In praise of code convolution avoidance: The shortest and simplest answer(Most adhering to the KISS philosophy) will be the accepted answer. DON'T use a library if you don't NEED to.

Answer 1

Here's the best I could come up with. First, I define \oldsection as the old \section macro, then use it to define a new \section command which first ends the previous multicolumn environment, unless it's the first section, in which case it does nothing, and then starts a new multicolumn environment with a section heading as defined by old section.

I also have to redefine \enddocument to end the final multicolumn.

This is not a very robust or advisable solution, but may work in a pinch.

\usepackage{multicol}
\usepackage{ifthen}
\let\oldsection\section
\renewcommand*{\section}[1]{%
    \ifthenelse{\thesection = 0}{}{\end{multicols}}%
    \begin{multicols}{2}[\oldsection{#1}]}
\let\oldend\enddocument
\renewcommand*{\enddocument}{\end{multicols}\oldend}

To used as follows:

\documentclass{article}
\usepackage{lipsum}
\usepackage{multicol}
\usepackage{ifthen}
\let\oldsection\section
\renewcommand*{\section}[1]{%
    \ifthenelse{\thesection = 0}{}{\end{multicols}}%
    \begin{multicols}{2}[\oldsection{#1}]}
\let\oldend\enddocument
\renewcommand*{\enddocument}{\end{multicols}\oldend}
\begin{document}
        \section{My first section}
        \lipsum[1-2]
        \section{Another section}
        \lipsum[3-4]
\end{document}

Answer 2

I don't really understand your question, but this might do what you want:

\newenvironment{xmulticols}[1]{\section{#1} \begin{multicols}{2}}{\end{multicols}}

This would only work if you only ever wanted 2 column layout, but is easily fixable to more columns.

I'd also recommend you also change how the section headings look (maybe make them centered?) to make clear that the section heading "covers" both columns...