%%
%% The LaTeX Companion, 2ed (second printing August 2004)
%%
%% Example 8-9-4 on page 528.
%%
%% Copyright (C) 2004 Frank Mittelbach, Michel Goossens,
%%    Johannes Braams, David Carlisle, and Chris Rowley
%%
%% It may be distributed and/or modified under the conditions
%% of the LaTeX Project Public License, either version 1.3
%% of this license or (at your option) any later version.
%%
%% See http://www.latex-project.org/lppl.txt for details.
%%

\documentclass{ttctexa}
\pagestyle{empty}
\setcounter{page}{6}
\setlength\textwidth{111.0pt}

% To show the difference better, we enlarge the default
% (not advisable for real documents):
\thickmuskip=7mu plus 5mu

\StartShownPreambleCommands
\usepackage[fleqn]{amsmath}   \usepackage{amssymb}
\DeclareMathSymbol\bneg   {\mathbin}{symbols}{"3A}
\DeclareMathSymbol\rsquare{\mathrel}{AMSa}{"03}
\StopShownPreambleCommands
\begin{document}
\[ a \neg b           \qquad  x \square           y + z \]
\[ a \mathbin{\neg} b \qquad  x \mathrel{\square} y + z \]
\[ a \bneg          b \qquad  x \rsquare          y + z \]
\end{document}