8.7 Displaylines

<..displaylines..>
 \def\tx:halign#1#2{\csname a:#1\endcsname
    \csname  \ifx \EndPicture\:Undef reg:#1\else o:#1:\fi
    \endcsname{#2}\csname b:#1\endcsname}
 -_-_-

<..displaylines..>+
 \def\:tempc#1{\tx:halign{displaylines}{#1}}
 \HLet\displaylines=\:tempc
                                     \catcode‘\#13 \catcode‘\!6
 \def\reg:displaylines!1{\tabskip\z@skip
    \SaveMkHalignConf:g{displaylines}\RecallTeXcr
    \MkHalign#{\hbox{$\@lign\displaystyle#$}}!1\crcr
    \EndMkHalign\RecallMkHalignConfig}
                                     \catcode‘\#=6 \catcode‘\!=12
 \NewConfigure{displaylines}{4}
 -_-_-

<..displaylinesNO..>
 \def\:temp#1{\displ@y
    <.html mode for displaylines.>%
    \TeXhalign {\hbox {$\@lign \displaystyle
        \ar:fld \R:dspln ##\r:dspln
        $}\crcr #1\aftergroup\t:dspln\crcr }}
 \HLet\displaylines=\:temp
 \NewConfigure{displaylines}[4]{%
    \c:def\T:dspln{#1}\c:def\t:dspln{#2}%
    \c:def\R:dspln{#3}\c:def\r:dspln{#4}}
 -_-_-

<..html mode for displaylinesNO..>
 \ifx \EndPicture\:UnDef
   \def\ar:fld{\T:dspln\global\let\ar:fld=\empty}%
 \else \let\ar:fld=\empty
 \fi
 -_-_-

When option ‘no-halign’ is up, the command ‘\h:noalign’ is undefined.

<..restore nohalignNO..>
 \csname h:noalign\endcsname
 -_-_-

<..plain,latex utilities..>
 \:CheckOption{no-halign} \if:Option \else
    \def\:temp{\everycr{}}
    \HLet\displ@y=\:temp
 \fi
 -_-_-

[test data]