Print a macro I created in a package

Question

Based on the answer I received to Print a short title in the header, I've created the macro \handoutheader in a .sty file I use as the template for my conference presentations.

\newcommand\@confname{} % create macro for name of conference
\newcommand\confname[1]{\renewcommand\@confname{#1}}
\newcommand\@confplace{} % create macro for place of conference
\newcommand\confplace[1]{\renewcommand\@confplace{#1}}
\newcommand\@confdate{} % create macro for date of conference
\newcommand\confdate[1]{\renewcommand\@confdate{#1}}
\newcommand{\handoutheader}{%
    My name \hfill \@confname\\
    My affiliation \hfill \@confplace\\
    My e-mail address \hfill \@confdate\\} % make handout header
\AtBeginDocument{\setlength{\parindent}{0pt}\handoutheader}

The logic is that I specify in the preamble of the .tex file for the handout what the name, place, and date of the conference is, and then the template creates a header on the handout with that information.

Now, I'd like to print the date of my presentation in the handout text. How do I do that? I've tried \confdate and \@confdate, but neither works.

\documentclass{article}
\usepackage{filecontents}

\begin{filecontents}{mystyle.sty}
%% My package starts here
\NeedsTeXFormat{LaTeX2e}
\ProvidesPackage{mystyle}
\newcommand\@confname{} % create macro for name of conference
\newcommand\confname[1]{\renewcommand\@confname{#1}}
\newcommand\@confplace{} % create macro for place of conference
\newcommand\confplace[1]{\renewcommand\@confplace{#1}}
\newcommand\@confdate{} % create macro for date of conference
\newcommand\confdate[1]{\renewcommand\@confdate{#1}}
\newcommand{\handoutheader}{%
    My name \hfill \@confname\\
    My affiliation \hfill \@confplace\\
    My e-mail address \hfill \@confdate\\} % make handout header
\AtBeginDocument{\setlength{\parindent}{0pt}\handoutheader}
\endinput
%% And ends here
\end{filecontents}

\usepackage{mystyle}
\confname{Name of conference}
\confplace{Place of conference}
\confdate{Date of conference}

\begin{document}
\vspace{2ex}\\
After hearing my talk, you will remember the date \confdate\ for the rest of your life.\\
After hearing my talk, you will remember the date \@confdate\ for the rest of your life.\\
\end{document} 

Answer 1

The two main problems were:

1. To use the @ in macro mames you need to use \makeatletter and \makeatother. See the references below.

2. The definition

    \newcommand\confdate[1]{\renewcommand\@confdate{#1}}
   

   means that calling \confdate sets the value of \@confdate to the first parmamater. In your code the first line (which is commented out in the MWE below) was resetting the value of \@confdate to be blank, which was then printed out in the subsequent call to \@confdate. Comenting out that call fixes the problem.

Notes:

• I'd recommend you not use \\ at the end of a new line. Just leave a blank line to indicate a new paragraph break.
• If you don't want to use \makeatletter just don't use a macro name that has an @ in it, or define a macro such as \ShowConfDate shown in the MWE.

References

• What do \makeatletter and \makeatother do? and
• \makeatletter explained

Code:

\documentclass{article}
\usepackage{filecontents}
\begin{filecontents}{mystyle.sty}
%% My package starts here
\NeedsTeXFormat{LaTeX2e}
\ProvidesPackage{mystyle}
\newcommand@confname{} % create macro for name of conference
\newcommand\confname[1]{\renewcommand@confname{#1}}
\newcommand@confplace{} % create macro for place of conference
\newcommand\confplace[1]{\renewcommand@confplace{#1}}
\newcommand@confdate{} % create macro for date of conference
\newcommand\confdate[1]{\renewcommand@confdate{#1}}
\newcommand\ShowConfDate{@confdate}%
\newcommand{\handoutheader}{%
    My name \hfill @confname\
    My affiliation \hfill @confplace\
    My e-mail address \hfill @confdate\} % make handout header
\AtBeginDocument{\setlength{\parindent}{0pt}\handoutheader}
\endinput
%% And ends here
\end{filecontents}
\usepackage{mystyle}
\confname{Name of conference}
\confplace{Place of conference}
\confdate{Date of conference}
\begin{document}
\makeatletter
%After hearing my talk, you will remember the date \confdate\ for the rest of your life.
After hearing my talk, you will remember the date @confdate\ for the rest of your life.
\makeatother
\medskip
If you don't want to be using \verb|\makeatletter| you can use \verb|\ShowConfDate| as in:
``The date is \ShowConfDate."
\end{document} 

Answer 2

In your example, \confdate takes an argument. Therefore, when you use

...remember the date \confdate\ for the rest of your life.

the \ (control space) is grabbed as the argument and placed inside \@confdate. That's why your output resembles

...remember the date for the rest of your life.

On the other hand, when you use

...remember the date \@confdate\ for the rest of your life.

the interpretation is to call \@, which inserts a very large \spacefactor - and what remains is confdate . As such, the output is

...remember the date confdate for the rest of your life.

Ideally you should create yourself a macro that shows the "privilege content". In the case below, I've created \printdate which sets \@confdate - the macro the holds the date.

\documentclass{article}
\usepackage{filecontents}

\begin{filecontents}{mystyle.sty}
%% My package starts here
\NeedsTeXFormat{LaTeX2e}
\ProvidesPackage{mystyle}
\newcommand\@confname{} % create macro for name of conference
\newcommand\confname[1]{\renewcommand\@confname{#1}}
\newcommand\@confplace{} % create macro for place of conference
\newcommand\confplace[1]{\renewcommand\@confplace{#1}}
\newcommand\@confdate{} % create macro for date of conference
\newcommand\confdate[1]{\renewcommand\@confdate{#1}}
\newcommand{\printdate}{\@confdate}
\newcommand{\handoutheader}{%
    My name \hfill \@confname\\
    My affiliation \hfill \@confplace\\
    My date \hfill \@confdate\\} % make handout header
\AtBeginDocument{\setlength{\parindent}{0pt}\handoutheader}
\endinput
%% And ends here
\end{filecontents}

\usepackage{mystyle}
\confname{Name of conference}
\confplace{Place of conference}
\confdate{Date of conference}

\begin{document}

\bigskip

After hearing my talk, you will remember the date \printdate{} for the rest of your life.
\end{document}

Answer 3

If you don't need to allocate new name for printing version of the macro \confname, you can define more intelligent version of such macro: if the equal sign immediately follows then the value is stored else the value is used. Example:

The test: \confname\         % value is used, empty value is printed as default.
\confname={Name}             % the value "Name" is stored.
The second test: \confname\  % the value "Name" is printed.

The implementation looks like:

\def\confname{\futurelet\next\confnameA}
\def\confnameA{\ifx\next=\expandafter\confnameB \else \confnameC\fi}
\def\confnameB=#1{\def\confnameC{#1}}
\def\confnameC{}

But we are lazy to write this code three times (for \confname, \confplace, \confdate). So, we can create a more intelligent macro:

\def\sdef#1{\expandafter\def\csname#1\endcsname}
\def\setmacro#1{%
   \sdef{#1}{\expandafter\futurelet\expandafter\next\csname#1.A\endcsname}%
   \sdef{#1.A}{\ifx\next=\csname#1.B\expandafter\endcsname \else \csname#1.C\endcsname\fi}%
   \sdef{#1.B}=##1{\sdef{#1.C}{##1}}%
}
\setmacro{confname} \setmacro{confplace} \setmacro{confdate}

You can insert this code to your .sty file instead \newcommand\@confname...\newcommand\confdate and you can replace the \@confname etc. by \confname etc. in the body of your macro \handoutheader. And, of course, the usage is slightly different:

\confname={Name of conference}
\confplace={Place of conference}
\confdate={Date of conference}