General ⇒ Best of two tests for empty argument

[woj-k]

Hi everyone,

I'm recently using a lot of macros that have to check if an argument is supplied empty (usually an optional argument, but I don't suppose that matters). In other people's code I noticed two typical ways of doing it in plain LaTeX.

Code: Select all

\documentclass{minimal}

\newcommand*{\detokenizetest}[1][]{\if\relax\detokenize{#1}\relax Empty.\else Not empty.\fi}
\newcommand*{\emptytest}[1][]{\def\optional{#1}\ifx\optional\empty Empty.\else Not empty.\fi}

\begin{document}
\detokenizetest[]

\emptytest[]

\detokenizetest[foo]

\emptytest[foo]
\end{document}

My question is: is there any way in which one of the above is superior to the other, or could either fail in certain circumstances? Is \ifx effectively a shorthand for \if and \detokenize{}, or do I have this all wrong in my head?

Many thanks for any advice! (and happy holidays)

[Johannes_B]

Package etoolbox provides some general facilities for testing, package xparse provides a few flags to test if an argument is empty. Xparse is used to define interfaces for user commands.


Really depends on what you are trying to do in the end.

[josephwright]

Test using \detokenize is expandable and therefore more general.