General ⇒ check if a parameter is empty

[kostka]

I want to have a command that does one thing if the parameter is empty, and another if it is nonempty. In pseudocode, something like the following:

Code: Select all

\newcommand{\card}[1]{
if #1 is empty:
Empty argument.
else:
The argument is #1.
end if
}

I could find information on checking if a macro is empty, but it didn't work for an argument. Is there a solution for this? Many thanks.

Tim

[phi]

Code: Select all

\ifx&#1&%
  % #1 is empty
\else
  % #1 is nonempty
\fi

The etoolbox package offers \ifstrempty, a more robust and “LaTeX-like” solution.

[kostka]

Thanks very much, I like that format the best. I also found the following way to do it:

Code: Select all

\usepackage{ifthen}

\newcommand{\card}[1]{
\ifthenelse{\equal{#1}{}}{Empty.}{Nonempty.}
}

Tim

[JakobHeiss]

Code: Select all

\isempty{#1}

is a good alternative instead of

Code: Select all

\equal{#1}{}}

So, in your example, I would use

Code: Select all

\newcommand{\card}[1]{
\ifthenelse{\isempty{#1}}{Empty.}{Nonempty.}
}