Hello Moses (uh ... I hope that's the name and Brooks is the surname ... :)), thank you very much for your email; it's very detailed and useful, which is why I've only replied this late (well, also because vacation-style RL popped in, but I digress :)) I'll address a couple of points replying under the relevant text. Monday, August 2, 2004 Brooks Moses wrote:
This inconvenience happens to show up in t-amsl.tex's "align" and "gather" implementations, which is one place where I really need that compatibility function. However, it turns out that there's a simple way to rewrite the implementation so to avoid needing \grabuntil.
Mostly, this works on the fact that the definition of Plain TeX's \eqalign function can be split apart into a before and after part, as follows:
\def\starteqalign{\null\,\vcenter\bgroup \openup\jot {\mathsurround=0pt}% \ialign\bgroup
\strut\hfil$\displaystyle{##}$&$\displaystyle{{}##}$\hfil \crcr} \def\stopeqalign{\crcr\egroup\egroup\,}
(This, aside from the \bgroup's and \egroup's, is copied directly from Appendix B of The TeXbook.) Thus, we could expand the instances of \eqalign in the \startalign and \startgather definitions, shuffle things around appropriately, and obtain the following:
\def\startalign{\startformula \let\\\cr \starteqalign} \def\stopalign{\crcr\stopeqalign\stopformula}
\def\startgather{\startformula \def\\{\cr&}% \starteqalign&} \def\stopgather{\crcr\stopeqalign\stopformula}
This exactly duplicates the existing functionality in the t-amsl.tex package.
Stop #1. I *enormously* love this idea. Have you been running test cases with this code instead of the one in t-amsl? If so, then I'll put it in the official t-amsl instantly.
However, that functionality could be improved to be a better match to what's provided in amsmath.tex; in particular, align should accept multiple columns of equations, and gather should center its lines. Thus, I propose that the following redefinitions be included in t-amsl:
\def\startalign{\startformula \let\\\cr \null\vcenter\bgroup \openup\jot {\mathsurround=0pt}% \everycr={}\tabskip=4pt plus1fil \halign to \displaywidth\bgroup \strut\hfil$\displaystyle{##}$% \tabskip=0pt &$\displaystyle{{}##}$\hfil% \tabskip=4pt plus1fil &&\hfil$\displaystyle{##}$% \tabskip=0pt &$\displaystyle{{}##}$\hfil% \tabskip=4pt plus1fil \crcr} \def\stopalign{\crcr\crcr\egroup\egroup\stopformula}
\def\startgather{\startformula \let\\\cr \null\,\vcenter\bgroup \openup\jot {\mathsurround=0pt}% \ialign\bgroup \strut\hfil$\displaystyle{##}$\hfil \crcr} \def\stopgather{\crcr\crcr\egroup\egroup\,\stopformula}
I like it. The only thing I would fix is that instead of the fixed 0pt and 4pt I would set up some \dimens (\intersomethingspacing or so). What do you think? And again, if you have actually been using this code instead of the one in t-amsl, I'll be happy to add it.
Also, a similar method can be used to replicate the split environment (which, unlike the above, should go inside an explicit \startformula and \stopformula pair). I propose the following definition be added as well:
\def\startsplit{% \let\\\cr \null\,\vcenter\bgroup \openup\jot {\mathsurround=0pt}% \ialign\bgroup
\strut\hfil$\displaystyle{##}$&$\displaystyle{{}##}$\hfil \crcr} \def\stopsplit{\crcr\egroup\egroup\,}
This still doesn't address the fact that the lines in the align and gather environments are not given individual equation numbers as they should be, but I think that is a project for another day.
Yeah, equation numbering in ConTeXt is something which I left "for another day" myself (I need it for the nath package as well).
P.S. A question: is it intentional that the array environment in t-amsl produces notably different spacing than LaTeX's array environment?
No, it's simply due to the fact that I haven't even bother to check if it were or not, because I didn't care either way :) The parameters are there. We'd only have to check how to use it within the ConTeXt spacing framework. -- Giuseppe "Oblomov" Bilotta