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
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