%% overlay.sty = overlay and align two symbols, respecting changing styles
%% see \TeX\ and TUG News vol 3 no 2 pp 10-11 for documentation
 
\def\loverlay#1#2{\mathpalette\@overlay{{#1}{#2}{}{\hfil}}}
\def\overlay#1#2{\mathpalette\@overlay{{#1}{#2}{\hfil}{\hfil}}}
\def\roverlay#1#2{\mathpalette\@overlay{{#1}{#2}{\hfil}{}}}
   % calls to \@overlay look like
   %    \@overlay\textstyle{{x}{y}{\hfil}{\hfil}}
 
\def\@overlay#1#2{\@@overlay#1#2}
   % strip brackets from 2nd arg, to get
   %    \@@overlay\textstyle{x}{y}{\hfil}{\hfil}

 
\def\@@overlay#1#2#3#4#5{{%
   \def\overlaystyle{#1}%
   \setbox0=\hbox{\m@th$\overlaystyle#2$}%
   \setbox1=\hbox{\m@th$\overlaystyle#3$}%
   \ifdim \wd0<\wd1 \setbox2=\box1 \setbox1=\box0 \setbox0=\box2\fi
      % \box0 is now the wider box
   \rlap{\hbox to\wd0{#4\box1\relax#5}}\box0%
}}