# [texhax] help with identifying some macros

Reinhard Kotucha reinhard.kotucha at web.de
Fri Oct 16 00:49:13 CEST 2009

On 15 October 2009 P. R. Stanley wrote:

> Hi folks
> \strut, \vtop and lblot. I'd be grateful for a brief description of
> each, more precisely, the general effect on the presentation.
>
> Here's an example of two of them in use taken from The Z Notation: a
> Reference Manual by Michael Spivey.
>
> $birthday$:
> > known = \{\,{\rm John, Mike, Susan}\,\} \\ > \also > birthday = \{\,\vtop{\halign{\strut#\hfil&{}\mapsto{}#\hfil\cr > John& 25--Mar,\cr > Mike& 20--Dec,\cr > Susan& 20--Dec\,\}.\cr}} >
> Truth be told I've seldom come across anything so cryptic. For
> example, what does the "#" signify?

consult a tutorial.  A few of them are available on-line, for example:

http://www.ctan.org/pub/tex-archive/info/impatient/book.pdf

\halign is explained on page 178.

BTW, plain TeX is not really cryptic.  Try to understand this code:

Regards,
Reinhard

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