[OS X TeX] Using align with "or"

[Ross Moore]

Hi David,

On 18/04/2011, at 8:35 AM, David Arnold wrote:

> Bruno et al,
> 
> This is precisely what I needed. But now I think I also need an explanation. We have:
> 
> \begin{alignat}{5}
> 
> But the first row has 9 ampersands. I've stumbled into solutions like this on my own, but I just don't understand the use of the ampersands.

Lee Witt said:

>>>  If you want to align n columns use 2n-1 &s

The point is that the alignment at each ampersand alternates:
   right alignment, then left alignment.

So if you have columns each with an alignment point "inside" the content,
then you need "&&" between the columns,

  viz.

    A&=B   &&   C&=D   && ...

> Is this use of the ampersands explained in any documentation?

Try  The LaTeX Companion    1st or 2nd editions.


> 
> D.
> 
> P.S. Also, is there any way to spread out the output a bit? 


   try the variants:

       \begin{xalignat}{5}
        ....

or

       \begin{xxalignat}{5}
        ....

and use  {alignat*}  {xalignat*}  if you don't want equation numbers.
 {xxalignat} suppresses them anyway.


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> 
> 
> D.
> 
> 
> On Apr 17, 2011, at 12:56 PM, Bruno Voisin wrote:
> 
>> Le 17 avr. 2011 ? 21:48, Lee D. Witt a ?crit :
>>> Have you tried "alignat"? You specify the number of "columns" to align. If you want to align n columns use 2n-1 &s
>>> 
>> \begin{alignat}{5}
>> u      &=0 & \quad\text{or}\quad  && u+4    &=0  & \quad\text{or}\quad  && u-4    &=0 \\
>> u      &=0 &&&                       u      &=-4 &&&                       u      &=4 \\
>> \log x &=0 &&&                       \log x &=-4 &&&                       \log x &=4
>> \end{alignat}
>> 
>> Bruno


Hope this helps,

	Ross

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Ross Moore                                       ross.moore at mq.edu.au 
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