[NTG-context] intertext for aligned equations

Mon Mar 27 09:23:34 CEST 2006

Hi,
I was looking at trying to implement something similar to
amsmath's intertext command. I can get the basic functionality working
as follows.

\def\startintertext#1\stopintertext{%
\noalign{#1}\NR}

\startformula \startalign
\NC A_1 \NC= \left| \int_0^1 (x^2 - 3x)\, dx \right|
+ \left| \int_1^2 (x^2 -5x + 6)\, dx \right| \NR
\startintertext
Take limis of both integrals %\input tufte
\stopintertext
\NC \NC = \left| \frac{x^3}{3} - \frac{3}{2} x^2 \right|_0^1
+ \left| \frac {x ^3}{3} - 7 \frac{5}{2} x^2 + 6x \right|_1^2 \NR
\NC \NC = \left| - \frac{7}{6} \right| + \left|\frac{14}{3} -
\frac{23}{6}\right| = \frac{7}{6} + \frac{5}{6} = 2 \NR
\stopalign \stopformula

This seems to be working fine. However, \intertext defined in
amsmath.sty seems to be doing  a lot more (I just can't figure out
what it is doing?) Can someone suggest how to make the above command
more robust on the lines of \intertext?

%----- from amsmath.sty -------------
\def\intertext@{%
\def\intertext##1{%
\ifvmode\else\\\@empty\fi
\noalign{%
\penalty\postdisplaypenalty\vskip\belowdisplayskip
\vbox{\normalbaselines
\ifdim\linewidth=\columnwidth
\else \parshape\@ne \@totalleftmargin \linewidth
\fi
\noindent##1\par}%
\penalty\predisplaypenalty\vskip\abovedisplayskip%
}%
}}

Thanks,