%%
%% The LaTeX Companion, 3ed
%%
%% Example 11-4-2 on page II-163 in "amsmath, mathtools, extarrows --- Decorated arrows".
%%
%% 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{tlc3examargin}
\pagestyle{empty}
\setcounter{page}{6}
\setlength\textwidth{153.0pt}
% Shorten the vertical size of the example ...
\AtBeginDocument{%
\setlength\abovedisplayskip{.8\abovedisplayskip}%
\setlength\belowdisplayskip{.8\belowdisplayskip}%
}
%StartShownPreambleCommands
\usepackage{mathtools}
%StopShownPreambleCommands
\begin{document}
\begin{gather}
A \xLeftarrow{\ x} B \xRightarrow[y\ ]{}
C \xLeftrightarrow[y]{\ x\ } D \\
A \xhookleftarrow{x} B \xhookrightarrow[bbb]{a} C \\
\xleftharpoondown{} \xleftharpoonup{}
\xleftrightharpoons{xxx} \xrightleftharpoons[yy]{}
\xrightharpoondown{} \xrightharpoonup{} \\
\xmapsto{x>0} A \xleftrightarrow[\text{letters}]{} Z
\end{gather}
\end{document}
