\let\>=\noindent
\def\qed{{\parfillskip=0pt\allowbreak\hfill\nobreak $\spadesuit$\par}}
\def\qeditem{{\parfillskip=0pt\hfill\rlap{\hskip\rightskip\llap{$\spadesuit$}}\par}}
+\def\qedmath{\eqno{\spadesuit}}
\def\FIXME#1{\>{\bo TODO:} #1}
\def\symdiff{\mathbin{\Delta}}
\def\rack#1#2{\setbox0=\hbox{#1}\hbox to \wd0{#2}}
\def\examplen{\example\labelx}
\def\problemn{\problem\labelx}
+\def\paran#1{\para {\sl #1:}}
+
\def\proof{\noindent {\sl Proof.}\enspace}
\def\proofsketch{\noindent {\sl Proof sketch.}\enspace}