Re: A few questions about aligned maths

[Morgan Brassel <morgan.brassel@free.fr>]

On Sun, 23 Mar 2008, Aditya Mahajan wrote:

> On Thu, 13 Mar 2008, Morgan Brassel wrote:
>> 3) Aditya, I saw your remark in your 'My Way' concerning the 'multline'
>> environment. I must admit I would really be glad to see it appear in
>> ConTeXt! I'm afraid I'm not able to implement it myself... I use it a
>> lot with amsmath: when a formula is just too long for one line, I put it
>> on two with multline. The first part of the formula is left aligned on the
>> first line, and the second part is right aligned on the second line. It seems
>> impossible to get the same result with only 'align'. Would it be difficult
>> to make it available in ConTeXt?
>
> Here is my first attempt. Completely bare-bones right now, but short
> enough to show what needs to be done.
>
> \unprotect
> \def\startmathlines
>   {\def\stop@math{$}
>    \def\NC{}
>    \def\NR{\def\NC{\cr}}
>    % Hack for number. Should be done by measuring the width of the number
>    \scratchdimen\dimexpr\displaywidth-4em \relax
>    \vbox \bgroup
>    \halign\bgroup
>     \hbox to \scratchdimen
>       {\hfil \strut
>         $\mathsurround\zeropoint\displaystyle{}## \stop@math
>        \hfil}%
>        \crcr
>        \hfilneg}
>
> \def\stopmathlines
>   {\hfilneg
>    \crcr
>    \egroup
>    \egroup}
> \protect
>
> \starttext
>
> \placeformula \startformula \startmathlines
>   \NC f(x) = (a+b)^n \NR
>   \NC = a^n + n \cdot a^{n-1} b + \cdots + n \cdot a b^{n-1} + b^n \NR
>   \NC = a^n + n \cdot a^{n-1} b + \cdots + n \cdot a b^{n-1} + b^n \NR
> \stopmathlines \stopformula
>
> \stoptext
>
> Taking care of [align=left|right] should be easy. This version will not
> break across pages. I cannot figure out how to get rid of the outer \vbox.
> Any suggestions?
>
> Aditya

Sorry that I can't help you with the implementation, Aditya... I just want 
to confirm that your new macro perfectly fits my needs. I hope it will 
make it into the core, it really is useful!

As always, a big thanks for your time and patience!
Morgan
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