Own cite command

Question

I want to create a certain cite command that is pretty similar to the original one:

\newcommand{\mycite}[2][]{\hspace{30pt}\cite{#2}{#1}}

The problem is that when I only write \mycite{test}. Then there will be

[Test, ]

but it should be

[Test]

because I omitted the optional argument. I tried it with the package xparse. But there I got the same result with the following code

\NewDocumentCommand\mycite{O{}m}{%
  \cite[#1]{#2}%
}

What do I do wrong? Could you help me?

Answer 1

There's no check if the optional argument of \mycite is present or not. So \mycite{#2} will still call \cite[]{#2} with an empty optional argument for \cite, meaning to typeset , in the list.

I added the 'traditional' way to check for the optional argument and the xparse method (much easier!)

Note: Bibliography related packages might change the \cite command already. This is not covered here.

\documentclass{article}

\usepackage{etoolbox}
\usepackage{xparse}

\makeatletter

\newcommand{\@myotherciteopt}[2][]{%
  \hspace{30pt}%
  \ifblank{#1}{%
    \cite{#2}%
  }{%
    \cite[#1]{#2}%
  }%
}

\newcommand{\@myothercitenoopt}[1]{%
  \@myotherciteopt[]{#1}%
}

\newcommand{\myothercite}{%
  \@ifnextchar[{\@myotherciteopt}{\@myothercitenoopt}%
}

\makeatother

\NewDocumentCommand\mycite{om}{%
  \hspace{30pt}%
  \IfValueTF{#1}{%
    \cite[#1]{#2}%
  }{%
    \cite{#2}%
  }%
}


\begin{document}

\mycite{Lam94}

\myothercite{Lam94}

Now with options:

\mycite[Ms. Ann Elk]{Lam94}

\myothercite[Ms. Ann Elk]{Lam94}

\bibliographystyle{alpha}

\bibliography{biblio}

\end{document}