Re: [NTG-context] LaTeX array equivalence with multiline \lbrace

26 Jan 2006

      Renaud AUBIN wrote:
...
I've read the post [NTG-context] Math Cases and I'm interested to have 
the possibility to do this kind of numbering:
{ b , if whatever     (1a)
 a ={
    { c,  otherwise       (1b)
...
If I understand you correctly, then something like this
\definealign[cases][left={\left\{}, right={\right.}, n=2, 
align={left,left}]
will give us \startcases, \stopcases which works like \cases. Such a 
feature will be very useful.
Is it possible to define left|right in such a way that
\definealign[important][left={\framed\bgroup},right={\egroup}]
results in a frame around the equations (and does not include the equation 
numbers), that is the frame is as broad as the width of the largest 
equation that follows. This mechanism can be used to highlight equations.
Also, in another post, I had asked if it is possible to have cases that 
are numbered, that is, can I get
{ b , if whatever     (1a)
a ={
   { c,  otherwise       (1b)
This is not important, but will be nice to have.
something like this?
\unprotect 

\definesystemvariable{ce}
\def\v!mathcases     {mathcases}
\def\c!numberdistance{numberdistance}

\def\setupmathcases
  {\dodoubleempty\dosetupmathcases}

\def\dosetupmathcases[#1][#2]%
  {\ifsecondargument
     \getparameters[\??ce#1][#2]%
   \else
     \getparameters[\??ce][#1]%
   \fi}

\let\currentmathcases\empty

\def\mathcasesparameter#1%
  {\executeifdefined{\??ce\currentmathcases#1}{\executeifdefined{\??ce#1}\empty}}

\setupmathcases
  [\c!distance=1em,
   \c!numberdistance=2.5em]

\def\definemathcases
  {\dodoubleempty\dodefinemathcases}

\def\dodefinemathcases[#1]% [#2]%
  {\setvalue{\e!start#1}{\dodoubleempty\dostartmathcases[#1]}%
   \setvalue{\e!stop #1}{\dostopmathcases}%
   \setupmathcases[#1]}% [#2]

\definemathcases[cases]
\definemathcases[\v!mathcases]

\def\dodocasesNC
  {\gdef\docasesNC{\endmath&}}

\let\docasesNR\doalignNR

\def\dostartmathcases[#1][#2]%
  {\begingroup
   \edef\currentmathcases{#1}%
   \doifassignmentelse{#2}{\setupmathcases[#1][#2]}\donothing
   \left\{%
   \,%
   \vcenter\bgroup
   \pushmacro\docasesNC
   \let\endmath\relax
   \def\NC{\docasesNC}%
   \def\MC{\docasesNC\ifmmode\else$\def\endmath{$}\fi}%
   \global\let\docasesNC\dodocasesNC
   \def\NR{\endmath&\global\let\docasesNC\dodocasesNC\doxxdoubleempty\docasesNR}%
   \normalbaselines
   \mathsurround\zeropoint
   \everycr\emptytoks
   \tabskip\zeropoint
   \global\eqaligncolumn\plusone
   \halign\bgroup
        \span$##$\hfil
       &\hskip\mathcasesparameter\c!distance\relax\popmacro\docasesNC##\hfil
       &\hskip\mathcasesparameter\c!numberdistance\relax\span\textineqalign{##}%
     \crcr} % todo: number

\def\dostopmathcases
  {\crcr
   \egroup
   \popmacro\docasesNC
   \egroup
   \right.
   \endgroup}

\protect

\showframe

\placeformula \startformula \startcases
\NC 2 \NC $ y > 0 $ \NR
\NC 7 \NC $ x = 7 $ \NR[+]
\NC 4 \NC otherwise \NR
\stopcases \stopformula

\placeformula \startformula x
\startcases
\NC 2 \NC $ y > 0 $ \NR[+]
\NC 7 \NC $ x = 7 $ \NR
\NC 4 \NC otherwise \NR
\stopcases
\stopformula

\placeformula \startformula \startcases
\NC 2 \NC $ y > 0 $ \NR
\NC 7 \NC $ x = 7 $ \NR
\NC 4 \NC otherwise \NR
\stopcases \stopformula

\placeformula \startformula x
\startcases
\NC 2 \NC $ y > 0 $ \NR
\NC 7 \NC $ x = 7 $ \NR
\NC 4 \NC otherwise \NR
\stopcases
\stopformula

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