wrap LaTeX command in environment

Question

How can I wrap a LaTeX command in an environment? In essence, how can I turn \\somecommand{contents} into \\begin{somecommand} contents \\end{somecommand}? I have tried the obvi

Answer 1

define command

\newcommnad{eqn}{1}{\begin{equation}#1\end{equation}}

will change

\eqn{x^2=y}

to

\begin{equation}
  x^2=y
\end{equation}

I think