% A small macro for Tex82 or Latex.  You can prevent a file of
% macros from being loaded twice by putting
%        \input maybeload
%        \thisfileis{<dirname>filename}
% in the macro file.  -- eb@oz 6/27/86
\global\def\thisfileis#1{\if T\csname #1=loaded\endcsname \endinput
  \else \global\expandafter\def\csname #1=loaded\endcsname{T}\fi}
%
% If you like, you can conditionalize the \input maybeload with the
% incantation
% \ifx\thisfileis\anUndefinedMacro\input maybeload \fi
% instead of just \input maybeload.
%