I see, it is either the nuisance of having to type \& etc. in the text, or the nuisance of having to wrap everything like \halign in \unprotect..\protect and then resorting to \& again.
At least there is nothing amiss with \halign itself, which is reassuring. However, I do not feel secure with these little deviations from the orginal TeX.
Hans van der Meer
On 18 Apr 2013, at 3:03 PM, Wolfgang Schuster mailto:schuster.wolfgang@gmail.com>
wrote:
Am 18.04.2013 um 14:55 schrieb "Meer, H. van der" mailto:H.vanderMeer@uva.nl>:
There seems something very much amiss with \halign in later ConTeXt versions.
This typesets fine in PlainTeX and is an example taken from a textbook.
\tabskip=1em\halign{%
\hfil\it#\hfil&\hfil#\hfil&#&\hfil#\crA&B&C&D\cr}
Also in contextversion 2012.05.30 (from a TeXlive distribution).
But it fails at least in ConTeXt ver: 2013.03.20 10:34 MKIV
and in ConTeXt ver: 2013.04.16 12:08 MKIV beta
with the following error
! Only one # is allowed per tab.
system > tex > error on line 5 in file fixedwidth.tex: Only one # is allowed per tab ...
1 \starttext
2 contextversion=\contextversion\par
3 \tabskip=1em
4 \halign{%
5 >> \hfil\it#\hfil&\hfil#\hfil&#&\hfil#\cr
6 A&B&C&D\cr}
7 \stoptext
l.5 \hfil\it#\hfil&\hfil#
\hfil&#&\hfil#\cr
Why? How primitive it may be, I would like to use \halign now and then.
The error message is misleading because the problem is & and not #.
One of the changes for MkIV was to make _, ^ and & normal characters
in the document (the first two still works for math). For code writing this
doesn’t matter because & has it’s normal meaning when you use
\unprotect … \protect but it can’t be used in the document.
Wolfgang
