[Tex/LaTex] Example environment

environmentsexamples

I was wondering if there is any formal environment for specifying 'examples' through out the text. If not, which environments do you recommend?

Best Answer

You could use the amsthm package. As per their recommendations, which is what most people use, you should define the environment as

\theoremstyle{definition}
\newtheorem{exmp}{Example}[section]

and than use is as

\begin{exmp}
This is the example.
\end{exmp}

Note however, that the above definition will give the examples its own counter. If you already have theorems and definitions using the thm-counter, you might want to consider using

\newtheorem[thm]{exmp}

since it can be very confusing for the reader if you have Theorem 3, Lemma 3, Definition 3 and Example 3 on different pages.

Related Solutions

[Tex/LaTex] LaTeX example environment

Here a simple solution with rule:

\documentclass{article}
\usepackage{xcolor}
\usepackage{ntheorem,lipsum}
\theoremseparator{:}
\newtheorem*{example}{Example}
\newtheorem*{solution}{Solution}
\newlength\outerlinewidth
\newlength\interline
\newlength\hangleft
\newenvironment{block}{%
 \trivlist\item\relax\par%
 \noindent\rlap{\hspace*{-\hangleft}\color{gray}%
   \rule{\dimexpr \hangleft+\linewidth\relax}{\outerlinewidth}%
   }%
 }{\par%
 \noindent\rlap{\hspace*{-\hangleft}\color{gray}%
   \rule{\dimexpr \hangleft+\linewidth\relax}{\outerlinewidth}
   }%
   \endtrivlist}
\newcommand*\blockline{\par\noindent%
       \begingroup\color{gray}%
       \rule{\linewidth\relax}{\interline}\endgroup\par%
}


%Set parameter:
\setlength{\outerlinewidth}{6pt} %height of the outer line
\setlength{\interline}{2pt} %height of the inter line
\setlength{\hangleft}{1cm} % left indention
\begin{document}
\begin{block}
\begin{example}[Rear clock ahead]
\lipsum[1]
\end{example}
\begin{solution}
\lipsum[2]
\end{solution}
\blockline
\begin{example}[Rear clock ahead]
\lipsum[1]
\end{example}
\begin{solution}
\lipsum[2]
\end{solution}
\end{block}
\end{document}

enter image description here

EDIT

Here a solution with mdframed

\documentclass{article}
\usepackage{microtype}
\usepackage{xcolor}
\usepackage{ntheorem,lipsum}
\usepackage[framemethod=default]{mdframed}
\usepackage{showframe}

\mdfdefinestyle{block}{%
   rightmargin=0pt,
   innerrightmargin=0pt,
   skipabove=\topskip,
   skipbelow=\topskip,
   leftline=false,
   rightline=false,
   leftmargin=-1cm,
   innerleftmargin=1cm,
   linecolor=gray,
   linewidth=6pt
}

\newmdenv[style=block,ntheorem]{block}


\theoremseparator{:}
\newtheorem*{example}{Example}
\newtheorem*{solution}{Solution}
\newlength\outerlinewidth
\newlength\interline
\newcommand*\blockline{\par\noindent%
       \begingroup\color{gray}%
       \rule{\linewidth\relax}{\interline}\endgroup\par%
}
%Set parameter:
\setlength{\interline}{2pt} %height of the inter line

\begin{document}
\begin{block}
\begin{example}[Rear clock ahead]
\lipsum[1]
\end{example}
\begin{solution}
\lipsum[2]
\end{solution}
\blockline
\begin{example}[Rear clock ahead]
\lipsum[1]
\end{example}
\begin{solution}
\lipsum[2]
\end{solution}
\end{block}
\end{document}

EDIT 2

Here a solution with mdframed in combination with etoolbox. Of course you can use the solution without using mdframed.

\documentclass{article}
\usepackage{microtype}
\usepackage{xcolor}
\usepackage{ntheorem,lipsum}
\usepackage[framemethod=default]{mdframed}
\usepackage{showframe}

\mdfdefinestyle{block}{%
   rightmargin=0pt,
   innerrightmargin=0pt,
   skipabove=\topskip,
   skipbelow=\topskip,
   leftline=false,
   rightline=false,
   leftmargin=-1cm,
   innerleftmargin=1cm,
   linecolor=gray,
   linewidth=6pt
}

\newmdenv[style=block,ntheorem]{block}


\theoremseparator{:}
\theorembodyfont{}
\newtheorem*{example}{Example}
\newtheorem*{solution}{Solution}

\newtoggle{env:example}
\newtoggle{env:solution}
\newtoggle{env:block}
\settoggle{env:solution}{false}
\settoggle{env:example}{false}
\settoggle{env:block}{false}

\BeforeBeginEnvironment{block}%
    {\settoggle{env:block}{true}
     \settoggle{env:solution}{false}
     \settoggle{env:example}{false}}

\AfterEndEnvironment{block}%
    {\settoggle{env:solution}{false}
     \settoggle{env:block}{false}
     \settoggle{env:example}{false}}

\BeforeBeginEnvironment{example}%
    {\ifboolexpr{ test {\iftoggle{env:block}}
                  and 
                  test {\iftoggle{env:example}}}%
                 {\settoggle{env:example}{true}}{}
     \iftoggle{env:example}{\blockline}{}}

\AfterEndEnvironment{example}%
    {\settoggle{env:example}{true}}

\newlength\outerlinewidth
\newlength\interline
\newcommand*\blockline{\par\noindent%
       \begingroup\color{gray}%
       \rule{\linewidth\relax}{\interline}\endgroup\par%
}
%Set parameter:
\setlength{\interline}{2pt} %height of the inter line

\begin{document}
\begin{block}
\begin{example}[Rear clock ahead]
\lipsum[1]
\end{example}
\begin{solution}
\lipsum[2]
\end{solution}
%\blockline
\begin{example}[Rear clock ahead]
\lipsum[1]
\end{example}
\begin{solution}
\lipsum[2]
\end{solution}
\end{block}
\end{document}

[Tex/LaTex] define a new Example environment

This is just a partial answer (for a complete answer, go to the last exampe). I used the thmtools package as a front-end for amsthm to define a theorem-like structure.

The use of

  \interlinepenalty 10000

in postheadhook prevents pagebreaks as requested.

\documentclass{book}
\usepackage{xcolor}
\usepackage{amsthm}
\usepackage{amssymb}
\usepackage{thmtools}
\usepackage{lipsum}

\colorlet{myred}{red!80!black}

\declaretheoremstyle[
spaceabove=\topsep, spacebelow=\topsep,
headfont=\normalfont\color{myred},
notefont=\mdseries\color{myred}, notebraces={(}{)},
bodyfont=\normalfont,
postheadspace=\newline,
headpunct=,
numberwithin=chapter,
postheadhook=\leavevmode%
  \interlinepenalty 10000%
  \vskip-1.3\baselineskip%
  \noindent{\color{myred}\rule{\textwidth}{1pt}}%
  \interlinepenalty 10000%
  \vskip0.3\baselineskip\noindent,
qed=\textcolor{myred}{$\blacksquare$}
]{mystyle}
\declaretheorem[style=mystyle]{example}

\renewcommand\theexample{\thechapter-\arabic{example}}

\begin{document}

\chapter{Test Chapter}
%\lipsum[1-3]
\begin{example}
\lipsum*[2]
\end{example}

\end{document}

enter image description here

The only thing that remains unsolved is the positioning of the end-mark when the last line in the environment belongs to a displayed math expression. Quite frankly I wouldn't know how to conditionally change the end-mark placement.

Here's another possibility using this time the mdframed package; the end-mark is provided using the \xqed macro defined in the document linked in the page Theorems in AMS-LaTeX of the AMS-FAQ.:

\documentclass{book}
\usepackage[framemethod=tikz]{mdframed}
\usepackage{amssymb}
\usepackage{lipsum}
\usepackage{etoolbox}

\newcommand{\xqed}[1]{%
  \leavevmode\unskip\penalty9999 \hbox{}\nobreak\hfill
  \quad\hbox{\ensuremath{#1}}}

\AtBeginEnvironment{example}{\stepcounter{example}}
\AtEndEnvironment{example}{\xqed{\textcolor{myred}{\blacksquare}}}

\colorlet{myred}{red!80!black}

\newmdenv[
  hidealllines=true,
  frametitle={Example~\theexample},
  frametitlerule=true,
  frametitlerulecolor=myred,
  frametitlerulewidth=2pt,
  frametitlefont=\bfseries\color{myred},
  innerleftmargin=0pt,
  innerrightmargin=0pt
]{example}

\newcounter{example}[chapter]
\renewcommand\theexample{\thechapter-\arabic{example}}

\begin{document}

\chapter{Test Chapter}
\begin{example}
\lipsum*[2]
\end{example}

\end{document}

enter image description here

Here's now a possible complete solution; instead of conditionally redefining the behaviour of the end-marks (which could be really difficult), the user can manually select the lexample environment which behaves like example, but placing the end-mark to the left:

\documentclass{book}
\usepackage[framemethod=tikz]{mdframed}
\usepackage{amsmath}
\usepackage{amssymb}
\usepackage{etoolbox}

\newlength\mylen

\newcommand{\xxqed}[1]{%
  \settowidth\mylen{$#1$}%
  \vskip-2\baselineskip\hspace*{-\mylen}\llap{\hbox{\ensuremath{#1}}}%
}

\newcommand{\xqed}[1]{%
  \leavevmode\unskip\penalty9999 \hbox{}\nobreak\hfill
  \quad\hbox{\ensuremath{#1}}}

\AtBeginEnvironment{example}{\stepcounter{example}}
\AtEndEnvironment{example}{\xqed{\textcolor{myred}{\blacksquare}}}

\AtBeginEnvironment{lexample}{\stepcounter{example}}
\AtEndEnvironment{lexample}{\xxqed{\textcolor{myred}{\blacksquare}}}

\colorlet{myred}{red!80!black}

\newmdenv[
  hidealllines=true,
  frametitle={Example~\theexample},
  frametitlerule=true,
  frametitlerulecolor=myred,
  frametitlerulewidth=2pt,
  frametitlefont=\bfseries\color{myred},
  innerleftmargin=0pt,
  innerrightmargin=0pt,
  skipabove=.6\topskip,
  skipbelow=.6\topskip
]{lexample}

\newmdenv[
  hidealllines=true,
  frametitle={Example~\theexample},
  frametitlerule=true,
  frametitlerulecolor=myred,
  frametitlerulewidth=2pt,
  frametitlefont=\bfseries\color{myred},
  innerleftmargin=0pt,
  innerrightmargin=0pt,
  skipabove=.6\topskip,
  skipbelow=.6\topskip
]{example}

\newcounter{example}[chapter]
\renewcommand\theexample{\thechapter-\arabic{example}}

\newcommand\Text{% just to generate text for the example
Quisque ullamcorper placerat ipsum. Cras nibh. Morbi vel justo vitae lacus
tincidunt ultrices. Lorem ipsum dolor sit amet, consectetuer adipiscing elit. In
hac habitasse platea dictumst. Integer tempus convallis augue. Etiam facilisis.
Nunc elementum fermentum wisi. Aenean placerat. Ut imperdiet, enim sed
gravida sollicitudin, felis odio placerat quam, ac pulvinar elit purus eget enim.
Nunc vitae tortor. Proin tempus nibh sit amet nisl.
}

\begin{document}

\chapter{Test Chapter}
\begin{lexample}
\Text
\begin{align}
a &= b \\
&= c 
\end{align}
\end{lexample}
\Text
\begin{example}
\Text
\end{example}

\end{document}

enter image description here

Best Answer

Related Solutions

[Tex/LaTex] LaTeX example environment

[Tex/LaTex] define a new Example environment

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