How do I make a command to display a custom title page?

Question

I followed the advice on the question What do \makeatletter and \makeatother do? to try to make a custom command that displays a custom title page, but it is not working.

./article.tex:17: You can't use `\spacefactor' in vertical mode.\@ ->\spacefactor
                  \@m
l.17 \makecustomtitle

Sorry, but I'm not programmed to handle this case;
I'll just pretend that you didn't ask for it.
If you're in the wrong mode, you might be able to
return to the right one by typing `I}' or `I$' or `I\par'.
./article.tex:17: Missing $ inserted.<inserted text>
                $
l.17 \makecustomtitle

I've inserted a begin-math/end-math symbol since I think
you left one out. Proceed, with fingers crossed.
./example.tex:17: You can't use `\spacefactor' in math mode.\@ ->\spacefactor
                  \@m
l.17 \makecustomtitle

Sorry, but I'm not programmed to handle this case;
I'll just pretend that you didn't ask for it.
If you're in the wrong mode, you might be able to
return to the right one by typing `I}' or `I$' or `I\par'.
./example.tex:17: Missing $ inserted.<inserted text>
                $
l.17 \makecustomtitle

I've inserted a begin-math/end-math symbol since I think
you left one out. Proceed, with fingers crossed.

What follows is the simplified code:

\documentclass[12pt]{article}

\newcommand{\makecustomtitle}{
\begin{titlepage}
  \makeatletter

  \@title by \@author

  \makeatother
\end{titlepage}
}

\begin{document}
\title{Please, be my title}
\author{Andres Riofrio}

\makecustomtitle

Take on me.

\end{document}

Answer 1

You need to move the \makeatletter and \makeatother outside of the \newcommand.

\makeatletter
\newcommand{\makecustomtitle}{%
  \begin{titlepage}
    \@title by \@author
  \end{titlepage}
}
\makeatother

The difference is that in the above set-up the category codes are changed at the time of definition; in your set-up they were attempting to change at the time of use.

Note that I've also added % to the end of the first line. Have a look at these links:

• What is the use of percent signs (%) at the end of lines?
• What do \makeatletter and \makeatother do?