Guide to LaTeX (4th Edition) (Tools and Techniques

360 Chapter 16. Letters
\DeclareOption*{\PassOptionsToClass{\CurrentOption}{letter}}
\ProcessOptions
\LoadClass[a4paper]{letter}
This completes the preliminaries. So far, we have read in the standard
letter class, along with the package ifthen, and defined a new option
that is not present in the original class. Otherwise, all options and
functions are unchanged, so far.
We now define the new ‘name’ commands to contain language-sensitive
text, such as ‘Subject’, which are not provided for in the basic class. The
actual definitions will be executed by two commands \englishnames and
\germannames.
\newcommand{\englishnames}{%
\newcommand{\yrefname}{\textsl{Your Ref.}}
\newcommand{\ymailname}{\textsl{Your letter from}}
\newcommand{\myrefname}{\textsl{Our Ref.}}
\newcommand{\subjectname}{\textsl{Subject}}
\newcommand{\telephonename}{Telephone}
\newcommand{\stationname}{Train Station}
\newcommand{\germanname}{GERMANY}
\newcommand{\telcode}{[49]-5556-401}
\newcommand{\postcode}{D--37191}
}
\newcommand{\germannames}{%
. . . . . . . . . . . . . . . . . . . . .
\newcommand{\telcode}{(05556) 401}
\newcommand{\postcode}{37191}
}
\ifthenelse{\boolean{@german}}
{\RequirePackage{german}\germannames}{\englishnames}
The last lines test whether the flag @german has been set (by the option
german), and if so, the package german is loaded, and the German names
are defined, otherwise the English names. The package german already
translates the standard names commands \toname, \headtoname, and
\pagename, so they are not included in \germannames.
Having settled the language problem, we now attack those commands
for entering extra information in the header. Each of these stores its
text argument in an internal command for future use. First the internal
storage commands must be created.
\newcommand{\@yref}{} \newcommand{\@ymail}{}
\newcommand{\@myref}{} \newcommand{\@subject}{}
\newcommand{\@internet}{}
\newcommand{\yref}[1]{\renewcommand{\@yref}{\yrefname: #1}}