[NTG-context] Myway on using mathalign

Aditya Mahajan adityam at umich.edu
Thu Apr 6 07:17:30 CEST 2006

On Thu, 6 Apr 2006, WN wrote:

> adityam at umich.edu wrote:
>> On Wed, 5 Apr 2006, WN wrote:
>>> One thing I want to do with a set of subformula's is
>>> to reference the main formula but still subnumbering the equations
>>> like
>> Try this. Warning: I do not know everything that is happening here. There 
>> may be some unexpected side effects.
>> \unprotect
>> \def\placesubformulawithnumber{%
>>   \dodoubleempty\doplacesubformulawithnumber}
>> \def\doplacesubformulawithnumber[#1][#2]%#2 gobbles spaces
>>   {\iffirstargument
>>     \incrementnumber[\v!formula]
>>     \makesectionnumber[\v!formula]
>>     \rawreference{\s!for}{#1}{\composedsectionnumber}
>>   \else
>>     \incrementnumber[\v!formula]
>>   \fi\placesubformula}
>> \protect
>>> \starttext
>> %% > \incrementnumber[formula]
>> %% > \placesubformula
>> \placesubformulawithnumber[eqn1] %I need to think of a smaller name
>>> \startformula
>>> \startalign
>>> \NC div  \vec{E} \NC =  \epsilon_{0}^{-1} \rho  \NR[eqn1:A][a]
>>> \NC rot  \vec{E} \NC =  0 \NR
>>> \NC div  \vec{B} \NC =  0 \NR[eqn1:B][b]
>>> \NC rot  \vec{B} \NC =  \mu_{0} \vec{j} \NR
>>> \stopalign
>>> \stopformula
>>> See *\in[eqn1] *for the static Maxwell equations, where we are going to 
>>> examine \in[eqn1:A] a bit further ....
>>> \stoptext
>> Also, note that div and rot should be in text font. You should probably do
>> \startmathcollection[default]
>>   \definemathcommand [div]      [nolop] {\mfunction{div}}
>>   \definemathcommand [rot]      [nolop] {\mfunction{rot}}
>> \stopmathcollection
>> and use \div \rot etc.
> Hi Aditya,
> I tested your solution and it works great. I cannot see any problems 
> in my output. I wish I had your Tex programming skills, I am trying 
> to learn the language myself from the TexBook (D.Knuth) but I still 
> have a long way to go.

Well, I do not understand Tex. What I usually do is look at the 
context source, which is much easier to read than latex internals, and 
then copy from there, play around a bit, and sometimes things 

> Another test to check that the formula numbers work as expected
> \placeformula[kem-chapter-eqn11]
> \startformula
> \cases{
> \eqalign{
> \widehat{\vec{x}} &= - \vec{x} \cr
> \widehat{t} & = t \cr
> }}
> \quad \text{resp.} \quad
> \cases{\eqalign{
> \widehat{\vec{x}} &=  \vec{x} \cr
> \widehat{t} & = -t \cr
> }}
> \stopformula

How about


     \NC \widehat{\vec{x}} \NC= - \vec x \NR
     \NC \widehat t        \NC= t        \NR
   \quad \text{resp} \quad
     \NC \widehat{\vec{x}} \NC= \vec x \NR
     \NC \widehat t        \NC= -t     \NR

There is also startstop cases, but that does not give the correct 
spacing in this case. May be useful otherwise.

     \NC \widehat{\vec{x}} \MC= - \vec x \NR
     \NC \widehat t        \MC= t        \NR
% Read MC as Math Column, there is also the usual NC
% which gives a text column
   \quad \text{resp} \quad
     \NC \widehat{\vec{x}} \MC= \vec x \NR
     \NC \widehat t        \MC= -t     \NR


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