[NTG-context] eqnalign

Aditya Mahajan adityam at umich.edu
Mon Oct 2 11:59:13 CEST 2006

On Tue, 26 Sep 2006, Adam Duck wrote:

> Hello list,
> Is it possible to break eqalign across pages?  If not, is there any
> other possibility to have math formulas aligned and broken across
> pages?

It is possible, Taco has a patch for this, but the patch has not yet 
been included as it is not tested thoroughly. Taco's patch allows the 
multi-line equation to break at any line across the page. But this is 
not always the desired behaviour. Consider

f(x) = (x + 2)^2        .... (1)
      = 2x^2 + 4x + 4    .....(2)

It is not desirable to have a page break between (1) and (2). Given 
current tex's inablility for parsing display equations [1], the best 
way is to allow the user to specify where he/she wants a break. 
Something like

\startformula \startalign
  \NC ... \NC ... \NR
  \NC ... \NC ... \NR
  \NC ... \NC ... \NR
  \NC ... \NC ... \NR
\stopalign \stopformula

I think that it is possible to add such a macro. I will try to do this 
when a bit later in the week.

[1] By design, TeX is very intelligent when it comes to line breaking 
of text and inline math, but does nothing about line breaking of 
display math. It will be nice (though not at all easy to implement) if 
I could just write

$$ A very long formula $$

and TeX would decide where and how to break it across line (and 
possible across pages) depending on the values of some penalities.


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