What would be some way to enable a user to 'switch' easily between different blocks of code in a preamble?

Question

I have a set of Beamer slides with a variety of styles coded in the preamble. There is a block of code corresponding to each style. The idea in using the slides to to select one block of code corresponding to one style in order to use that style. Rather than instructing users to comment out every line of code for all styles not wanted, is there some way to enable the user to 'switch' easily between these different blocks of code in the preamble, such as setting a variable towards the top of the TeX file to the appropriate style? Thanks for any suggestions.

Out of curiosity, is there some way of doing a similar type of switching between different blocks of code in the body of the LaTeX document? Perhaps defining a block of code in a command would be sensible for this.

Answer 1

You can use \ifcase ...\or ... \or ... \fi conditional construct to do the job. In the following example, I use standalone for the sake of simplicity. Change \style definition to any positive integer (in the interval provided by \ifcase ...\or ... \fi) to switch among cases. For more details, read the following code.

\documentclass[preview,border=12pt,12pt]{standalone}
% define an interger variable
\edef\style{0}

\ifcase\style
% case 0:
\author{Donut E. Knot}
\or
% case 1:
\author{Donut Elephant Knot}
\or
% case 2:
\author{Steve Jobs}
\or
% case 3:
\author{Bill Gates}
\or
% case 4:
\author{Timothy Van Zandt}
\or
% case 5:
\author{Till Tantau}
\fi

\title{A journey to the west}

\begin{document}
\maketitle
\end{document}

Answer 2

This strategy lets you choose between two styles by changing one line at the beginning of the preamble:

\usepackage{etoolbox}
\newtoggle{production}

%\toggletrue{production}
\togglefalse{production}

Then, later in the preamble or in the document, as often as needed

\iftoggle{production}{%
   % one style here ...
}{%
   % else another ... 
}

For selection among more than two alternatives, you could use nested toggles, or wait for a better answer using more sophisticated logic.

Another alternative is to write separate preambles, then \input the right one as appropriate.

This can be done from the command line if you prefer.