subarray

<..equations of amsmath.sty..>+
                                     \catcode‘\#=13 \catcode‘\!=6
 \def\reg:subarray!1{%
   \vcenter\bgroup
   \Let@ \restore@math@cr \default@tag
   \baselineskip\fontdimen10 \scriptfont\tw@
   \advance\baselineskip\fontdimen12 \scriptfont\tw@
   \lineskip\thr@@\fontdimen8 \scriptfont\thr@@
   <.ialign amsmath subarray.>}
                                     \catcode‘\#=6 \catcode‘\!=12
 -_-_-

<..ialign amsmath subarray..>
 \let\e:subarray=\empty \let\f:subarray=\empty
 \everycr{}\SaveMkHalignConf:g{subarray}%\HRestore\noalign
 \MkHalign#{$\m@th\scriptstyle#$}%
 -_-_-

<..equations of amsmath.sty..>+
 \def\:tempc{\crcr\EndMkHalign
     \RecallMkHalignConfig \egroup\b:subarray}
 \HLet\endsubarray=\:tempc
 \def\:temp#1{\def\Hlcr{#1}\pic:MkHalign{subarray}{#1}}
 \HLet\subarray=\:temp
 \NewConfigure{subarray}{4}
 -_-_-