%%
%% The LaTeX Companion, 3ed
%%
%% Example A-5-5 on page II-690 in "ifthen --- Advanced control structures".
%%
%% Copyright (C) 2022 Frank Mittelbach
%%
%% It may be distributed and/or modified under the conditions
%% of the LaTeX Project Public License, either version 1.3c
%% of this license or (at your option) any later version.
%%
%% See https://www.latex-project.org/lppl.txt for details.
%%

\documentclass{tlc3exa}
\pagestyle{empty}
\setcounter{page}{6}
\setlength\textwidth{111.0pt}
%StartShownPreambleCommands
\usepackage{ifthen,shortvrb}  \MakeShortVerb\|
%StopShownPreambleCommands

\begin{document}
\newcommand\BB{\CC}\newcommand\CC{\DD}
\newcommand\DD{AA} \newcommand\EE{EE}
|\BB|=|\EE|?  \ifthenelse{\equal{\BB}{\EE}}{True}{False}.\par
|\BB|=|\CC|?  \ifthenelse{\equal{\BB}{\CC}}{True}{False}.\par
|\DD|=|\BB|?  \ifthenelse{\equal{\DD}{\BB}}{True}{False}.
\end{document}