From mboxrd@z Thu Jan  1 00:00:00 1970
From: Eric S Fraga <ucecesf@ucl.ac.uk>
Subject: Re: Re: [org-beamer] \alert
Date: Fri, 29 Jan 2010 12:23:32 +0000
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To: tcburt@rochester.rr.com
Cc: =?UTF-8?B?U8OpYmFzdGll?=, emacs-orgmode@gnu.org, =?UTF-8?B?bg==?= Vauban <wxhgmqzgwmuf@spammotel.com>, Carsten Dominik <carsten.dominik@gmail.com>

At Fri, 29 Jan 2010 06:26:21 -0500,
Tim Burt wrote:
> Eric S Fraga writes:
>  > For any LaTeX expert out there, is there an easy way to determine
>  > whether a particular macro has been defined?  If so, we wouldn't even
>  > need to check for beamer, simply for \alert.
> 
> Use the 
>   \ifx<command>\undefined ... \else ... \fi 
> construct to determine if a command already exists, and then to take
> action in the appropriate case.  Test the example below both as-is and
> with the first ~\newcommand*{\thisalert}~ commented out to see the
> different results.

[...]

> I hope this is of use,
> Tim

Thanks Tim.  Very helpful indeed!  

The following org-mode line does the job for me:

#+latex_header: \ifx\alert\undefined\let\alert\textbf\fi

If \alert is not defined, I have =alert= behave as =textbf=.
Alternatively, something like this also works:

#+latex_header: \ifx\alert\undefined\newcommand*{\alert}[1]{\textbf{#1}}\fi

in case one wants more control (e.g. could also change the colour to red).

eric