[NTG-context] mathmatrix and internal lines

[Hans Hagen]

On 11/26/2020 8:43 PM, Otared Kavian wrote:
> Hi Jean-Philippe,
> 
> A few weeks ago I saw briefly the discussion about Hans' message regarding \noalign and the the new definitions of \HR and \VR that you are sending. Indeed your solution works great !
> Just for the case other people may have the same question about writing block matrix, I copy below the whole example which can be found later in the mail archive.
> (For mkiv, I don't know how to do the same thing…).

The \noaligned permits a \protected definition. Otherwise one has to do 
something

\def\VR{\noalign\bgroup
   <command that picks up [#1]

that command then does the rule and ends the noalign. Also, that one 
cannot be \protected (a pitty in case one uses \expanded or so)

So ... a multistep approach. Plenty of that in mkiv.

> %%% begin block-matrix.tex
> % in LMTX defining \HR and \VR to create block matrices:
> \pushoverloadmode
> \noaligned\tolerant\protected\def\HR[#1]{\noalign{\hrule #1}}
> \popoverloadmode
> 
> \def\VR{\dosingleempty\doVR}
> \def\doVR[#1]{\NC \hskip-0.5em \vrule #1 \hskip-0.5em \NC}

given the \HR definition that should be

\tolerant\protected\def\VR[#1]{\NC ...\NC}

> \definemathmatrix[mymatrix]
> 	[left={\left(\,},
> 	right={\, \right)}]
> 
> \starttext	
> 
> \startformula
> 	\startmymatrix
> 		\NC A \VR  B \NR
> 		\HR
> 		\NC C \VR  D \NR
> 	\stopmymatrix
> \stopformula
> 
> \stoptext

Anyway, a feature like this should be in sync with other table 
mechanisms, so

\definemathmatrix
   [mymatrix]
   [left={\left\lparent\thinspace},
    right={\thinspace\right\rparent}]

\starttext

\startformula
	\startmymatrix
		\NC A \VL  B \NR
		\HL
		\NC C \VL  D \NR
	\stopmymatrix
\stopformula

\startformula
	\startmymatrix
		\NC A \VL[3,green]  B \NR
		\HL[10,red]
		\NC C \VL  D \NR
	\stopmymatrix
\stopformula

\stoptext

A bit more code needed but the next upload will have it. Of course you 
have to wikify it.

Hans

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