%%% Reversing text in 36 bytes (can you do better?)

% Jan Šustek presented a pearl titled ``Reversing text in 55 bytes'' the
% previous year.  It comprised the following macro for sending puzzle
% messages via SMS:


\def\##1{\ifx.#1\def\#{~.}\else\edef~{#1~}\fi\#}\def~{}\#dlrow\ olleH.

% Since length counts in text messages we propose the following version,
% which is only 36 bytes (if we count the total length of the macro
% definition and a call on ``Hello world.'' we get 70 bytes in Šustek’s
% version and 51 in ours):

\def~#1#2~{\ifx~#2~#1\else~#2~#1\fi}~.dlrow\ olleH~

% Let's trace the expansion of \verb|~|:
%   ~.dlrow\ olleH~
%   ~dlrow\ olleH~.
%   ~lrow\ olleH~d.
%   ~row\ olleH~ld.
%   ~ow\ olleH~rld.
%   ~w\ olleH~orld.
%   ~\ olleH~world.
%   ~olleH~\ world.
%   ~lleH~o\ world.
%   ~leH~lo\ world.
%   ~eH~llo\ world.
%   ~H~ello\ world.
%   Hello\ world.

% The beauty of this macro lies in symmetry: in the definition the
% tokens between \verb|\ifx| and \verb|\else| are exactly the same as
% tokens between \verb|\else| and \verb|\fi|.

% Can you do any better?

\end