\ShowPar \par{\HCondtrue\noindent}%
-_-_-
   
 
    \:CheckOption{no_^}
  
 \if:Option \else \:CheckOption{no_}\fi
  
 \if:Option \else
  
    \Configure{SUB}
  
       {\HCode{<sub>}}{\HCode{</sub>}}
  
 \fi
  
 \:CheckOption{no_^}
  
 \if:Option \else \:CheckOption{no^}\fi
  
 \if:Option \else
  
    \Configure{SUP}
  
       {\HCode{<sup>}}{\HCode{</sup>}}
  
 \fi
  
 \:CheckOption{no_^}
  
  \if:Option \else \:CheckOption{no_}\fi
  
  \if:Option \else \:CheckOption{no^}\fi
  
 \if:Option \else
  
    \Configure{SUBSUP}
  
       {\HCode{<sub>}}{\HCode{</sub><sup>}}{\HCode{</sup>}}
  
 \fi
  
 \Configure{left}
  
   {\Picture+{ \a:@Picture{left}}}
  
   {\aftergroup\EndPicture   }
  
 \Configure{mathchoice}{\PictureOff}{\PictureOn}
-_-_-
   
 
   \endgraf is safer than \par, because the latter may be redefined. For instance,
see p 262 in texbook.
    \let\MathPar=\empty
  
 \Configure{PicDisplay}
  
   {\edef\MathPar{\ifvmode par-\fi}\IgnorePar\endgraf\EndP
  
    \HCode{<center class="\MathPar math-display" \a:LRdir >}}
  
   {\HCode{</center>}}  {}  {class="\MathPar math-display" }
-_-_-
   
 
    \HCode{&\expandafter \ifx\csname U#2#1\endcsname\relax
  
                  #2#1\else \#x\csname U#2#1\endcsname\fi;}%
-_-_-
   
 
    xmlns="http://www.w3.org/1999/xhtml"
-_-_-
   
 
   
The \trap:base is to catch empty bases of exponents like, e.g., in $a^{^b}$.
    \def\MathRow#1{%
  
    \Configure{\expandafter\:gobble\string#1*}{*}%
  
       {<\a:mathml: mrow\Hnewline
  
          class="\expandafter\:gobble\string#1">}{</\a:mathml: mrow>}%
  
       {\Configure{\expandafter\:gobble\string#1}{}{}{}{}}#1}%
-_-_-
   
 
   
    \edef\sv:ignore{\if:nopar
  
     \noexpand\IgnorePar\else \noexpand\ShowPar\fi}%
-_-_-
   
 
   The \MathRow requests a <|.mrow\Hnewline>...</|.mrow>, instead of the
contributions of \mathop, \mathrel,...., for the next parameter.
   
Definitions like \def\mathbf#1{\a:mathbf#1\b:mathbf} can’t be done on
a global level, because \mathbf is just a name of a font. So, for instance,
\bf expands to \mathbf, and so $\bf R$ indirectly brings up the latter
command.
   
The default \left and \right in their default definition with tex produce
multi-part delimiters, from cmex, on large subformulas. Hence, the ‘’.’ below is
needed.