[texhax] if condition: is macro body empty?

[Lars Madsen]

Susan Dittmar wrote:
> Hi folk,
> 
> for (pdf)latex I am looking for a way to check whether the body of a macro
> is empty or not. At the moment, I use a construct using \equal{}{<macro>},
> but I have the impression that during evaluation of this construct some
> ugly side effects occur. I am sure there must be a better way.
> 
> Here's a short example (the final thing is much more complex, the \buffer
> being filled with parts of an \item list or with parts of a tabular):
> 
> %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
> \documentclass{article}
> \usepackage{ifthen}
> \newcommand{\buffer}{}
> \makeatletter
> % close to what I need:
> \newcommand{\fillbuffer}[1]{%
> 	\ifthenelse{\equal{\buffer}{}}%
> 	{\g at addto@macro{\buffer}{#1}}
> 	{\g at addto@macro{\buffer}{\newline #1}}
> }
> \makeatother
> \begin{document}
> 
> Filling the buffer may be called or not, and done here.
> \fillbuffer{First part.}
> \fillbuffer{Second part.}
> 
> Now use the contents of this buffer:
> 
> \buffer
> 
> \end{document}
> %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
> 
> 
> Any ideas please?
> 
> 	Susan
> 

I've use ifmtarg in my last project, had to use some \expandafter 
sometimes, but for my purpose it worked fine


-- 

/daleif