\unprotect
\def\dostartmathmatrix[#1][#2]%
  {\begingroup
   \edef\currentmathmatrix{#1}%
   \doifassignmentelse{#2}{\setupmathmatrix[#1][#2]}\donothing
   \null
   \executeifdefined{\??mx:\mathmatrixparameter\c!location}{\getvalue{\??mx:\v!lohi}}%
   \mathmatrixleft
   \mathmatrixbox\bgroup
   \pushmacro\domatrixNC
   \let\endmath\relax
   \def\NC{\domatrixNC}%
   \def\MC{\domatrixNC\ifmmode\else$\def\endmath{$}\fi}%
   \global\let\domatrixNC\dodomatrixNC
   \def\NR{\endmath\global\let\domatrixNC\dodomatrixNC\crcr}%
   \normalbaselines
   \mathsurround\zeropoint
   \everycr\emptytoks
   \tabskip\zeropoint
   \eqaligncolumn\zerocount % could be \!!counta
   \processcommacommand[\mathmatrixparameter\c!align]{\advance\eqaligncolumn\plusone\dosetmatrixcolumn}%
   \!!counta=\ifnum\eqaligncolumn>\!!counta \eqaligncolumn \else \plusone \fi
   \global\eqaligncolumn\plusone
   \preparemathmatrix } % uses !!counta

\def\buildmathmatrix % beware: etex only
  {\scratchtoks\emptytoks
   \expanded{\scratchtoks{\the\scratchtoks\the\!!toksa}}%
   \dorecurse{\numexpr\!!counta-\plusone\relax}
     {\expanded{\scratchtoks{\the\scratchtoks\the\!!toksb}}}%
   \expanded{\scratchtoks{\the\scratchtoks\the\!!toksc }}}
\protect

\loadmapfile[original-youngryu-tx.map]

\starttypescript [math] [modern,computer-modern,latin-modern,ams] [size]
    \definebodyfont [17.3pt,14.4pt,12pt,11pt,10pt,9pt] [mm] [mb=rsfs10 sa 1]
    \definebodyfont [8pt,7pt] [mm] [mb=rsfs7 sa 1]
    \definebodyfont [6pt,5pt,4pt] [mm] [mb=rsfs5 sa 1]
    \definebodyfont [28pt,24pt,18pt,17.3pt,14.4pt,12pt,11pt,10pt,9pt,8pt,7pt,6pt,5pt,4pt] [mm] [mc=txexa sa 1]
\stoptypescript

\startmathcollection [default]
\definemathsymbol [oiint]               [op] [mc] ["08] [mc] ["09]
\definemathsymbol [oiiint]              [op] [mc] ["29] [mc] ["2a]
\definemathsymbol [ointctrclockwise]    [op] [mc] ["0A] [mc] ["0B]
\definemathsymbol [ointclockwise]       [op] [mc] ["0C] [mc] ["0D]
\definemathsymbol [varointctrclockwise] [op] [mc] ["2B] [mc] ["2C]
\definemathsymbol [varointclockwise]    [op] [mc] ["2D] [mc] ["2E]
\definemathsymbol [iint]                [op] [mc] ["21] [mc] ["22]
\definemathsymbol [iiint]               [op] [mc] ["23] [mc] ["24]
\definemathsymbol [iiiint]              [op] [mc] ["25] [mc] ["26]
\definemathsymbol [idotsint]            [op] [mc] ["27] [mc] ["28]
\definemathsymbol [oiintctrclockwise]   [op] [mc] ["40] [mc] ["41]
\definemathsymbol [oiintclockwise]      [op] [mc] ["48] [mc] ["49]
\definemathsymbol [varoiintctrclockwise][op] [mc] ["4A] [mc] ["4B]
\definemathsymbol [varoiintclockwise]   [op] [mc] ["42] [mc] ["43]
\definemathsymbol [oiiintctrclockwise]  [op] [mc] ["44] [mc] ["45]
\definemathsymbol [oiiintclockwise]     [op] [mc] ["4C] [mc] ["4D]
\definemathsymbol [varoiiintctrclockwise][op] [mc] ["4E] [mc] ["4F]
\definemathsymbol [varoiiintclockwise]  [op] [mc] ["46] [mc] ["47]
\stopmathcollection
\definefamilysynonym [default] [scriptfamily] [mb]
\def\scr{\fam\purefamily{scriptfamily}}

\definetypeface[MyFace] [rm] [serif] [modern] [default] [encoding=texansi]
\definetypeface[MyFace] [mm] [math] [modern] [modern]  [encoding=texansi]

\setupbodyfont[MyFace,11pt]


\definemathmatrix[mycases][left={\left\{\,},right={\,\right.}]

\starttext
\startformula
\Delta =
\startmatrix[n=4,align={left,middle,left,right}]
\NC -aaa \NC vvvvv \NC -wwwwwwww \NC wwwwwwww \NR
\NC aaaa \NC -vvvvv \NC wwwwwwww \NC www \NR
\NC -bbbbb \NC vv \NC -wwww \NC wwwwwwww \NR
\NC bbbbb \NC -vvvvv \NC wwwwwwww \NC wwwwwwww \NR
\stopmatrix
\stopformula

\startformula
\startmatrix[align={right, left}]
\NC aa \NC vvvv \NR
\NC vvvvv \NC -vvvvv  \NR
\NC -vvvvv \NC vvvvv  \NR
\NC vv \NC -vvvvv  \NR
\stopmatrix
\stopformula

\startformula
 \startalign[n=4,align={left,middle,middle,right}]
 \NC aaa\NC b\NC cccc\NC d\NR
 \NC a\NC bbb\NC c\NC ddd\NR
 \stopalign
 \stopformula

 \startformula
 \startmycases[n=4,align={left,middle,middle,right}]
 \NC aaa\NC b\NC cccc\NC d\NR
 \NC a\NC bbb\NC c\NC ddd\NR
 \stopmycases
\stopformula
\section{Extra math symbols}
\startformula
\oiint
\oiiint
\ointctrclockwise
\ointclockwise
\varointctrclockwise
\varointclockwise
\iint
\iiint
\iiiint
\idotsint
\oiintctrclockwise
\oiintclockwise
\varoiintctrclockwise
\varoiintclockwise
\oiiintctrclockwise
\oiiintclockwise
\varoiiintctrclockwise
\varoiiintclockwise
\stopformula

\startformula
\alpha \beta \gamma \delta \mu \nu \eta \xi \sigma \epsilon \Gamma \Delta
\stopformula
\type{\scr ABCDEFGHIJKLMNOPQRSTUVWXYZ}
\startformula
{\scr ABCDEFGHIJKLMNOPQRSTUVWXYZ}
\stopformula
\type{\cal ABCDEFGHIJKLMNOPQRSTUVWXYZ}
\startformula
{\cal ABCDEFGHIJKLMNOPQRSTUVWXYZ}
\stopformula

\page
\section{Default math characters}
\showmathcharacters

\stoptext