%%
%% The LaTeX Companion, 3ed
%%
%% Example 11-4-23 on page II-172 in "mathtools, interval --- Properly spaced intervals".
%%
%% 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{165.0pt}

  % Shorten the vertical size of the example ...
  \AtBeginDocument{%
    \setlength\abovedisplayskip{.5\abovedisplayskip}%
    \setlength\belowdisplayskip{.8\belowdisplayskip}%
  }

%StartShownPreambleCommands
\usepackage{interval}
%StopShownPreambleCommands

\begin{document}
\[ \interval[open right]{a}{d} = \interval{a}{b} +
   \interval[open left]{b}{c} + \interval[open]{c}{e}
      - \interval[open right]{d}{e}                \]
\end{document}