[texhax] Finding blank argument to macro

Lars Madsen daleif at imf.au.dk
Tue Jun 29 10:25:32 CEST 2010

Michael Barr wrote:
> Here is a fragment of a macro I use to find if an argument is empty:
>     \setbox0\hbox{$#9$}%
>    \ifdim \wd0=0pt%
>    %%%%%%%% omitted what you do if arg empty
>    \else
>    %%%%%%%% omitted what you do if not
>    \fi
> It is based on commands supplied in the TeX engine and, therefore, 
> completely valid in (nearly) every version of TeX, including LaTeX.  
> (The reason for the (nearly) is that AMSTeX insists on killing certain 
> primitive commands, but standard LaTeX doesn't.)  Incidentally, \box0 is 
> a "scratch" box anyone can use, but don't expect to come back to it and 
> find whatever you put in it unchanged.
> Just a bit of a sermon.  There is no conflict between using LaTeX and 
> using TeX.  There is some (very little actually) between PLAIN TeX and 
> LaTeX and I have never understood the purists who insist on "pure 
> LaTeX", whatever that might mean.
> Michael Barr
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try the etoolbox it has some very good tests for empty arguments and 
many other nice features



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