Giuseppe and ConTeXt list members -
Having figured out how to use \grabuntil (see my previous messages to this list), I've realized that it's really an inconvenient solution in some cases, because it's searching for a literal bit of text rather than an end to the appropriate grouping level. (Apparently there isn't a way to do the latter in TeX, given that AMSmath's [EMAIL PROTECTED] also searches for literal text.) This means that, if I write a "LaTeX compatibility function" that does things like define \end{myenvironment} to expand to \stopmyenvironment, my redefinition will not work on any environments using \grabuntil.
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. 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}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.
- Brooks
P.S. A question: is it intentional that the array environment in t-amsl produces notably different spacing than LaTeX's array environment?
_______________________________________________ ntg-context mailing list [EMAIL PROTECTED] http://www.ntg.nl/mailman/listinfo/ntg-context
