[texhax] Finding blank argument to macro
Uwe Lueck
uwe.lueck at web.de
Tue Jun 29 16:46:57 CEST 2010
Jim Diamond <Jim.Diamond at acadiau.ca>, 27.05.2010 13:43:48:
> On Thu, May 27, 2010 at 07:17 (-0400), 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
>> \if
>
> Hmmm... what if #9 is
> \hbox to 0 pt{blah \hss}
> ?
>
> Arguably a pathological example, but arguably not.
Actually, Jim's example works like \rlap{blah } with LaTeX (Jim certainly knew but thought better not to tell) where \rlap is used for \lefteqn, for the tabbing environment, and for thanks-footnotes. So it is useful to append something on the right of a centered line without affecting the alignment. So much for "pathological".
Cheers,
Uwe.
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