[texhax] centering a box on the margin line

Aditya Mahajan adityam at umich.edu
Tue Nov 13 01:34:11 CET 2007

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

> Hi Aditya,
> > 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.

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