General ⇒ \newcommand and optional parameters

[kristianjohann]

Hi all!

CONTEXT.
For different journals one have to cite in different ways (in footnotes ore Harvard-citation style). To manage this in an easy way I created a cite-command (\mycite) with two optional and one mandatory parameters. This command can easily be redefined depending on a journals format.

PROBLEM.
If an optional argument is empty, then the respective parameter is identical with \empty. But the usual citation-command \cite that is used in my definition of \mycite implements (\cite[\empty][\empty]{carnap1928LogAuf}) different from (\cite[][]{carnap1928LogAuf}), namely: ( [Car28], p.) vs. ([Car28]). How to get out of (\cite[\empty][\empty]{carnap1928LogAuf}) the result ([Car28])?

FAILED-SOLUTION.
I think that it is a problem of expansion. I tried to expand first the arguments - but I only succeeded expanding the first argument: (\expandafter\cite\expandafter[\empty][\empty]{carnap1928LogAuf}) results in ([Car28], p.)

IMPLEMENTATION.

Code: Select all

\newcommand{\mycite}[1][\empty]{%
  \def\ArgI{#1}%
  \mycitemycite%
}
\newcommand\mycitemycite[1][\empty]{%
  \def\ArgII{#1}%
  \mycitemycitemycite%
}
\newcommand\mycitemycitemycite[1]{%
  (\cite[\ArgI][\ArgII]{#1})%
}

Thanks for your attention!

[sommerfee]

If an optional argument is empty, then the respective parameter is identical with \empty.

1. It's not clear to me why you use [\empty] as optional argument when defining your macros. Why don't you just use [] instead, e.g. \newcommand{\mycite}[1][]{...} ?

2. You can't use \expandafter here because you have two arguments to expand and you don't know what's inside these arguments. It could be something which doesn't like to get expanded before. So better use \edef and \noexpand instead, e.g.

Code: Select all

\newcommand\mycitemycitemycite[1]{%
  \edef\temp{(\noexpand\cite[\ArgI][\ArgII]{#1})}%
  \temp
}

[josephwright]

Looks like a job for xparse to me:

Code: Select all

\usepackage{xparse}
\NewDocumentCommand\mycite{O{}O{}m}{%
  (\cite[#1][#2]{#3})%
}

This avoids any \edef-worries.

[kristianjohann]

Hello Sommerfee!

Thank you very much for your solution (2.) - it worked perfectly well!
Ad 1.: I tried both: [] and [\empty] and got the same result, namely an empty sign in the citation; so I thought that [] is internally implemented as [\empty].

Thanks again and have a nice evening, Christian

[kristianjohann]

Hello josephwright!

Thank you very much for your solution - xparse also has done the job, but I tried to get a solution without loading an extra package.

Have a nice day, Christian

[localghost]

Now that the problem is solved, please be so kind and mark the topic (not the last post) accordingly as clearly written in the Board Rules (to be read before posting). Please keep that in mind for the future so that further reminders will not be necessary.


Thorsten