# [texhax] help with identifying some macros

Donald Arseneau asnd at triumf.ca
Fri Oct 16 11:42:46 CEST 2009

"P. R. Stanley" <prstanley at ntlworld.com> writes:

> Here's an example of two of them in use taken from The Z Notation: a
> Reference Manual by Michael Spivey.
>
> $birthday$:

He should be flogged for that!

> Is this a bit of LaTeX mixed up with ugly Plain TeX? Or is it a "Z" macro? > known = \{\,{\rm John, Mike, Susan}\,\} \\ The \rm is better, but I think those words are still in math mode. Horrible! > \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?

Look up the meaning and usage of \halign in The TeXbook or in
TeX by Topic; or skip it entirely!  The first line (up to \cr)
of \halign is a template, and # shows where the text of the
following rows is inserted in the template.

--
Donald Arseneau                          asnd at triumf.ca