# [texhax] centering a box on the margin line

Tue Nov 13 01:34:11 CET 2007

Quoting Reinhard Kotucha <reinhard.kotucha at web.de>:

>
> > You can enclose the box in a \clap.
>
> where is \clap defined?
>
> zaphod:~ # tex \\relax
> This is TeX, Version 3.141592 (Web2C 7.5.5)
>
> *\show\clap
>> \clap=undefined.

I am sorry, I did not test while posting. \clap is not defined by plain
tex. In fact, it is not even defined by latex. In my usual set of
packages it is defined by mathtools as

\providecommand*\clap[1]{\hb at xt@\z@{\hss#1\hss}}

that is \hbox to 0pt{\hss #1 \hss}, so it is same as the definition
that you gave. I always assumed that \clap was a plain tex macro.

Sorry for the noise.