Defining an environment shorthand in Latex using \newcommand

Question

I'd like to define a shorthand command for \begin{align*} and \end{align*}. When I write
\newcommand{\ba}{\begin{align*}}
it works fine. But when I write
\newcommand{\ea}{\end{align*}}
latex complains. It looks like it's interpreting it as part of the environment and is not happy with that. Anyone know how to fix this?

Answer 1

An alternative solution -- this is the code in the custom document class I use for everything:

\newcommand{\eq}[1]{\begin{align*}#1\end{align*}}

Usage:

\eq{
  x^2 + 9 &= 0
}

(Obviously, change the command name to suit your preference.)

Answer 2

A little testing shows that this appears to be fairly specific to the "align" environment from amsmath. For example,

\documentclass{article}

\usepackage{amsmath}

\newcommand{\bc}{\begin{center}}
\newcommand{\ec}{\end{center}}

\begin{document}

\bc
hello world
\ec

\end{document}

works fine. I'm not sure why align* doesn't work (it doesn't work without the star either); I suspect that the myriad expansions and aliases surrounding the align environment do something a little more complicated than a "traditional" LaTeX environment. However, I have found something that might just achieve the same objective for you:

\documentclass{article}

\usepackage{amsmath}

\newcommand{\ba}{\[\begin{aligned}}
\newcommand{\ea}{\end{aligned}\]}

\begin{document}

\ba
x^2 &= y^2 \\
z^2 &= t^2
\ea

\end{document}

Hope that helps!