%%% Reversing text in 55 bytes

% The following short macro \# reverses given text.

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

% The definition is only 55 bytes long, so one can use it to write a puzzled SMS to a \TeX-friend.

\#dlrow\ olleH.

% Notice that the space must be escaped. This is because all tokens with category 10
% (space tokens) are skipped when \TeX reads undelimited parameters of a macro.

\end