Alias ( to \begin{pmatrix}?

Question

I'm wondering if there's any way that I can alias the ( and ) buttons to \begin{pmatrix} and \end{pmatrix}, so that when I type those characters in math mode, LaTeX will magically replace them with the correct commands.

As far as I can tell there's no reason to use the "dumb" versions, and it would save me a whole lot of time. Is this possible?

I'm not actually asking how to redefine (. I'm asking LaTeX to replace all (s in math mode with \begin{pmatrix}.

Answer 1

Edit

The original question that I saw asked for \( ... \) to expand to \begin{pmatrix} ... \end{pmatrix} but, in fact, the OP wants ( ... ) to automatically expand to \begin{pmatrix} ... \end{pmatrix}. I voted to close this because it is a duplicate of Automatic left and right commands (see the answer of LSpice), and then the question was closed and reopened. So, I re-answer.

The trick to doing what the OP wants is to make ( and ) active characters. Once this is done, they can be redefined at will:

\documentclass{amsart}

\let\lparen=(\let\rparen=)           % save parentheses
\catcode`(=\active\catcode`)=\active % make them active
\def({\begin{pmatrix}}               % redefine them
\def){\end{pmatrix}}

\begin{document}

  \[    ( 1 & 0  & 1 \\ 0 & 1 & 0\\ 0 & 0 & 1 ) \]

\end{document}

With this code, if you want to type ( or ) then you need to use \lparen and \rparen. It is quite likely that this will have weird and not so wonderful side effects.

A slightly better approach would be to define an environment where ( and ) expand to give a pmatrix and outside of this they behave normally. Redefining catcodes inside an environment requires a little more gymnastics (see How could one change the catcodes inside the definition of an environment?):

\documentclass{amsart}

\let\lparen=(\let\rparen=)% save parentheses

\catcode`(=\active\catcode`)=\active% change catcode for newenvironment
\newenvironment{pequation}{%
  \catcode`(=\active\catcode`)=\active% make them active in environment
  \def({\begin{pmatrix}}% redefine them
  \def){\end{pmatrix}}%
  \equation%
}{\endequation}
\catcode`(=12\catcode`)=12% restore to original catcodes

\begin{document}

  \begin{pequation}
   ( 1 & 0  & 1 \\ 0 & 1 & 0\\ 0 & 0 & 1 )
  \end{pequation}

  $\sin(x)$
\end{document}

Original answer

You can do this if you really want to but, as the comments show, most people would recommend against doing this. The main issue is that, by default, LaTeX uses \( ... \) to typeset mathematics, so it is (almost) equivalent to $ ... $ --- in fact, by Are \( and \) preferable to dollar signs for math mode?, \(...\) provides better error messages. The \(...\) command is a counterpoint to the way LaTeX encourages us to typeset displayed equations using \[ ... \]. Note that \[ ... \] is not equivalent to $$ ... $$! See Why is \[ ... \] preferable to $$ ... $$?.

This said, you can override the definition of any command with \renewcommand (or \def). Overriding the definition of a command should be done with care because doing this might break something else.

These caveats aside, the following does what you want:

\documentclass{amsart}

\renewcommand\({\begin{pmatrix}}
\renewcommand\){\end{pmatrix}}

\begin{document}

Here is a wonderful matrix
\[    \( 1 & 0 & 1 \\ 0 & 1 & 0\\ 0 & 0 & 1\) \]

\end{document}

There may be unintended consequences but I think that this should be OK, although it may well confuse your coauthors! In my opinion, a better way to do this is to properly configure your editor:)

[I must confess that I used to redefine \( to be \bigl(, and \) to \bigr), so I am on dubious grounds with the moral statements above that you shouldn't do this!]