Re: math formula linebreak

[Hans Hagen <pragma@wxs.nl>]

On 9-8-2012 20:53, Aditya Mahajan wrote:
> On Thu, 9 Aug 2012, Sietse Brouwer wrote:
>
>> Steffen Wolfrum wrote:
>>>> them to break automatically ... is there a handy solution?
>>
>> Aditya Mahajan wrote:
>>> Short answer: No easy solution exists.
>>
>> Is this because allowing automatic line breaks in math mode is itself
>> hard to implement, or is the basic mechanism possible but preventing
>> stupid/ugly breakpoints is hard? Because I can imagine a 70 percent
>> solution being a big help already.
>
> Partly both.
>
> The question is not so much the difficulty in choosing break-points
> (which is easy: before all \mathbin atoms, after \mathpunct if needed,
> etc). The hard part is how to align the split up portions, and choosing
> different alignments changes the line widths, and therefore affect
> future line-breaks.
>
> The old manual of breqn (the one by Michel Jones) had some discussion on
> the different alignment of display math. They are also explained nicely
> in the book on typesetting math by AMS (I forget the author's name).
>
> In principle, one can follow the same approach as Knuth did for
> line-breaking text (define penalties and then solve a dynamic program to
> find the layout that gives the lowest score). The breqn package does
> implement such an algorithm that works well in most cases. I wish that
> the breqn algorithm were described somethere; then one could play around
> implementing it in luatex. Trying to read breqn code to understand the
> algorithm is very difficult.

When I'm done ceaning up the pending tex and lua code, I'll look into 
these issues. It's probably not that hard to come up with a solution in 
lua (one of the pet projects on my list).

Hans

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