% arara: pdflatex: { files: [latexindent]}
\subsection{Poly-switches}\label{sec:poly-switches}
 Every other field in the \texttt{modifyLineBreaks} field uses poly-switches, and can take
 one of the following%
 \announce{2017-08-21}*{blank line poly-switch} integer values:
 \index{modifying linebreaks! using poly-switches}
 \index{poly-switches!definition}
 \index{poly-switches!values}
 \index{poly-switches!off by default: set to 0}
 \begin{description}
  \item[$-1$] \emph{remove mode}: line breaks before or after the
   \emph{<part of thing>} can be removed (assuming that \texttt{preserveBlankLines} is
   set to \texttt{0});
  \item[0] \emph{off mode}: line breaks will not be modified for the
   \emph{<part of thing>} under consideration;
  \item[1] \emph{add mode}: a line break will be added before or after the
   \emph{<part of thing>} under consideration, assuming that
   there is not already a line break before or after the \emph{<part of thing>};
  \item[2] \emph{comment then add mode}: a comment symbol will be added, followed by a line break
   before or after the \emph{<part of thing>} under consideration, assuming that there is
   not already a comment and line break before or after the \emph{<part of thing>};
  \item[3] \emph{add then blank line mode}%
   \announce{2017-08-21}{blank line poly-switch}: a line break will be added before or after
   the \emph{<part of thing>} under consideration, assuming that there is not already a line
   break before or after the \emph{<part of thing>}, followed by a blank line;
  \item[4] \emph{add blank line mode}%
   \announce{2019-07-13}{blank line poly-switch}; a blank line will
   be added before or after the \emph{<part of thing>} under consideration, even if the
   \emph{<part of thing>} is already on its own line.
 \end{description}
 In the above, \emph{<part of thing>} refers to either the \emph{begin statement},
 \emph{body} or \emph{end statement} of the code blocks detailed in
 \vref{tab:code-blocks}. All poly-switches are \emph{off} by default;
 \texttt{latexindent.pl} searches first of all for per-name settings, and then followed by
 global per-thing settings.

\subsubsection{Poly-switches for environments}\label{sec:modifylinebreaks-environments}
 We start by viewing a snippet of \texttt{defaultSettings.yaml} in
 \cref{lst:environments-mlb}; note that it contains \emph{global} settings (immediately
 after the \texttt{environments} field) and that \emph{per-name} settings are also allowed
 -- in the case of \cref{lst:environments-mlb}, settings for \texttt{equation*} have been
 specified for demonstration. Note that all poly-switches are \emph{off} (set to 0) by
 default. \index{poly-switches!default values} \index{poly-switches!environment global
 example} \index{poly-switches!environment per-code block example}

 \cmhlistingsfromfile[style=modifylinebreaksEnv]{../defaultSettings.yaml}[width=.8\linewidth,before=\centering,MLB-TCB]{\texttt{environments}}{lst:environments-mlb}

 Let's begin with the simple example given in \cref{lst:env-mlb1-tex}; note that we have
 annotated key parts of the file using $\BeginStartsOnOwnLine$, $\BodyStartsOnOwnLine$,
 $\EndStartsOnOwnLine$ and $\EndFinishesWithLineBreak$, these will be related to fields
 specified in \cref{lst:environments-mlb}. \index{poly-switches!visualisation:
 $\BeginStartsOnOwnLine$, $\BodyStartsOnOwnLine$, $\EndStartsOnOwnLine$,
 $\EndFinishesWithLineBreak$}

 \begin{cmhlistings}[style=tcblatex,escapeinside={(*@}{@*)}]{\texttt{env-mlb1.tex}}{lst:env-mlb1-tex}
before words(*@$\BeginStartsOnOwnLine$@*) \begin{myenv}(*@$\BodyStartsOnOwnLine$@*)body of myenv(*@$\EndStartsOnOwnLine$@*)\end{myenv}(*@$\EndFinishesWithLineBreak$@*) after words
\end{cmhlistings}

 \paragraph{Adding line breaks: BeginStartsOnOwnLine and BodyStartsOnOwnLine}
  Let's explore \texttt{BeginStartsOnOwnLine} and \texttt{BodyStartsOnOwnLine} in
  \cref{lst:env-mlb1,lst:env-mlb2}, and in particular, let's allow each of them in turn to
  take a value of $1$. \index{modifying linebreaks! at the \emph{beginning} of a code
  block} \index{poly-switches!adding line breaks: set to 1}

  \begin{minipage}{.45\textwidth}
   \cmhlistingsfromfile[style=yaml-LST]{demonstrations/env-mlb1.yaml}[MLB-TCB]{\texttt{env-mlb1.yaml}}{lst:env-mlb1}
  \end{minipage}
  \hfill
  \begin{minipage}{.45\textwidth}
   \cmhlistingsfromfile[style=yaml-LST]{demonstrations/env-mlb2.yaml}[MLB-TCB]{\texttt{env-mlb2.yaml}}{lst:env-mlb2}
  \end{minipage}

  After running the following commands, \index{switches!-l demonstration}
  \index{switches!-m demonstration}
  \begin{commandshell}
latexindent.pl -m env-mlb.tex -l env-mlb1.yaml
latexindent.pl -m env-mlb.tex -l env-mlb2.yaml
\end{commandshell}
  the output is as in \cref{lst:env-mlb-mod1,lst:env-mlb-mod2} respectively.

  \begin{widepage}
   \begin{minipage}{.56\linewidth}
    \cmhlistingsfromfile{demonstrations/env-mlb-mod1.tex}{\texttt{env-mlb.tex} using \cref{lst:env-mlb1}}{lst:env-mlb-mod1}
   \end{minipage}
   \hfill
   \begin{minipage}{.43\linewidth}
    \cmhlistingsfromfile{demonstrations/env-mlb-mod2.tex}{\texttt{env-mlb.tex} using \cref{lst:env-mlb2}}{lst:env-mlb-mod2}
   \end{minipage}
  \end{widepage}

  There are a couple of points to note:
  \begin{itemize}
   \item in \cref{lst:env-mlb-mod1} a line break has been added at the point denoted by
         $\BeginStartsOnOwnLine$ in \cref{lst:env-mlb1-tex}; no other line breaks have been
         changed;
   \item in \cref{lst:env-mlb-mod2} a line break has been added at the point denoted by
         $\BodyStartsOnOwnLine$ in \cref{lst:env-mlb1-tex}; furthermore, note that the \emph{body}
         of \texttt{myenv} has received the appropriate (default) indentation.
  \end{itemize}

  Let's now change each of the \texttt{1} values in \cref{lst:env-mlb1,lst:env-mlb2} so
  that they are $2$ and save them into \texttt{env-mlb3.yaml} and \texttt{env-mlb4.yaml}
  respectively (see \cref{lst:env-mlb3,lst:env-mlb4}). \index{poly-switches!adding comments
  and then line breaks: set to 2}

  \begin{minipage}{.45\textwidth}
   \cmhlistingsfromfile[style=yaml-LST]{demonstrations/env-mlb3.yaml}[MLB-TCB]{\texttt{env-mlb3.yaml}}{lst:env-mlb3}
  \end{minipage}
  \hfill
  \begin{minipage}{.45\textwidth}
   \cmhlistingsfromfile[style=yaml-LST]{demonstrations/env-mlb4.yaml}[MLB-TCB]{\texttt{env-mlb4.yaml}}{lst:env-mlb4}
  \end{minipage}

  Upon running commands analogous to the above, we obtain
  \cref{lst:env-mlb-mod3,lst:env-mlb-mod4}.

  \begin{widepage}
   \begin{minipage}{.56\linewidth}
    \cmhlistingsfromfile{demonstrations/env-mlb-mod3.tex}{\texttt{env-mlb.tex} using \cref{lst:env-mlb3}}{lst:env-mlb-mod3}
   \end{minipage}
   \hfill
   \begin{minipage}{.43\linewidth}
    \cmhlistingsfromfile{demonstrations/env-mlb-mod4.tex}{\texttt{env-mlb.tex} using \cref{lst:env-mlb4}}{lst:env-mlb-mod4}
   \end{minipage}
  \end{widepage}

  Note that line breaks have been added as in \cref{lst:env-mlb-mod1,lst:env-mlb-mod2}, but
  this time a comment symbol has been added before adding the line break; in both cases,
  trailing horizontal space has been stripped before doing so.

  Let's \announce{2017-08-21}{demonstration of blank line poly-switch (3)} now change each
  of the \texttt{1} values in \cref{lst:env-mlb1,lst:env-mlb2} so that they are $3$ and
  save them into \texttt{env-mlb5.yaml} and \texttt{env-mlb6.yaml} respectively (see
  \cref{lst:env-mlb5,lst:env-mlb6}). \index{poly-switches!adding blank lines: set to 3}%

  \begin{minipage}{.45\textwidth}
   \cmhlistingsfromfile[style=yaml-LST]{demonstrations/env-mlb5.yaml}[MLB-TCB]{\texttt{env-mlb5.yaml}}{lst:env-mlb5}
  \end{minipage}
  \hfill
  \begin{minipage}{.45\textwidth}
   \cmhlistingsfromfile[style=yaml-LST]{demonstrations/env-mlb6.yaml}[MLB-TCB]{\texttt{env-mlb6.yaml}}{lst:env-mlb6}
  \end{minipage}

  Upon running commands analogous to the above, we obtain
  \cref{lst:env-mlb-mod5,lst:env-mlb-mod6}.

  \begin{widepage}
   \begin{minipage}{.56\linewidth}
    \cmhlistingsfromfile{demonstrations/env-mlb-mod5.tex}{\texttt{env-mlb.tex} using \cref{lst:env-mlb5}}{lst:env-mlb-mod5}
   \end{minipage}
   \hfill
   \begin{minipage}{.43\linewidth}
    \cmhlistingsfromfile{demonstrations/env-mlb-mod6.tex}{\texttt{env-mlb.tex} using \cref{lst:env-mlb6}}{lst:env-mlb-mod6}
   \end{minipage}
  \end{widepage}

  Note that line breaks have been added as in \cref{lst:env-mlb-mod1,lst:env-mlb-mod2}, but
  this time a \emph{blank line} has been added after adding the line break.

  Let's now change \announce{2019-07-13}{demonstration of new blank line poly-switch} each
  of the \texttt{1} values in \cref{lst:env-mlb5,lst:env-mlb6} so that they are $4$ and
  save them into \texttt{env-beg4.yaml} and \texttt{env-body4.yaml} respectively (see
  \cref{lst:env-beg4,lst:env-body4}). \index{poly-switches!adding blank lines (again"!):
  set to 4}%

  \begin{minipage}{.45\textwidth}
   \cmhlistingsfromfile[style=yaml-LST]{demonstrations/env-beg4.yaml}[MLB-TCB]{\texttt{env-beg4.yaml}}{lst:env-beg4}
  \end{minipage}
  \hfill
  \begin{minipage}{.45\textwidth}
   \cmhlistingsfromfile[style=yaml-LST]{demonstrations/env-body4.yaml}[MLB-TCB]{\texttt{env-body4.yaml}}{lst:env-body4}
  \end{minipage}

  We will demonstrate this poly-switch value using the code in \cref{lst:env-mlb1-text}.

  \cmhlistingsfromfile{demonstrations/env-mlb1.tex}{\texttt{env-mlb1.tex}}{lst:env-mlb1-text}

  Upon running the commands \index{switches!-l demonstration} \index{switches!-m
  demonstration}
  \begin{commandshell}
latexindent.pl -m env-mlb1.tex -l env-beg4.yaml
latexindent.pl -m env-mlb.1tex -l env-body4.yaml
\end{commandshell}

  then we receive the respective outputs in \cref{lst:env-mlb1-beg4,lst:env-mlb1-body4}.

  \begin{cmhtcbraster}[raster column skip=.1\linewidth]
   \cmhlistingsfromfile{demonstrations/env-mlb1-beg4.tex}{\texttt{env-mlb1.tex} using \cref{lst:env-beg4}}{lst:env-mlb1-beg4}
   \cmhlistingsfromfile{demonstrations/env-mlb1-body4.tex}{\texttt{env-mlb1.tex} using \cref{lst:env-body4}}{lst:env-mlb1-body4}
  \end{cmhtcbraster}

  We note in particular that, by design, for this value of the poly-switches:
  \begin{enumerate}
   \item in \cref{lst:env-mlb1-beg4} a blank line has been inserted before the \lstinline!\begin!
         statement, even though the \lstinline!\begin! statement was already on its own line;
   \item in \cref{lst:env-mlb1-body4} a blank line has been inserted before the beginning of the
         \emph{body}, even though it already began on its own line.
  \end{enumerate}

 \paragraph{Adding line breaks using EndStartsOnOwnLine and EndFinishesWithLineBreak}
  Let's explore \texttt{EndStartsOnOwnLine} and \texttt{EndFinishesWithLineBreak} in
  \cref{lst:env-mlb7,lst:env-mlb8}, and in particular, let's allow each of them in turn to
  take a value of $1$. \index{modifying linebreaks! at the \emph{end} of a code block}
  \index{poly-switches!adding line breaks: set to 1}

  \begin{minipage}{.49\textwidth}
   \cmhlistingsfromfile[style=yaml-LST]{demonstrations/env-mlb7.yaml}[MLB-TCB]{\texttt{env-mlb7.yaml}}{lst:env-mlb7}
  \end{minipage}
  \hfill
  \begin{minipage}{.49\textwidth}
   \cmhlistingsfromfile[style=yaml-LST]{demonstrations/env-mlb8.yaml}[MLB-TCB]{\texttt{env-mlb8.yaml}}{lst:env-mlb8}
  \end{minipage}

  After running the following commands, \index{switches!-l demonstration}
  \index{switches!-m demonstration}
  \begin{commandshell}
latexindent.pl -m env-mlb.tex -l env-mlb7.yaml
latexindent.pl -m env-mlb.tex -l env-mlb8.yaml
\end{commandshell}
  the output is as in \cref{lst:env-mlb-mod7,lst:env-mlb-mod8}.

  \begin{widepage}
   \begin{minipage}{.42\linewidth}
    \cmhlistingsfromfile{demonstrations/env-mlb-mod7.tex}{\texttt{env-mlb.tex} using \cref{lst:env-mlb7}}{lst:env-mlb-mod7}
   \end{minipage}
   \hfill
   \begin{minipage}{.57\linewidth}
    \cmhlistingsfromfile{demonstrations/env-mlb-mod8.tex}{\texttt{env-mlb.tex} using \cref{lst:env-mlb8}}{lst:env-mlb-mod8}
   \end{minipage}
  \end{widepage}

  There are a couple of points to note:
  \begin{itemize}
   \item in \cref{lst:env-mlb-mod7} a line break has been added at the point denoted by
         $\EndStartsOnOwnLine$ in \vref{lst:env-mlb1-tex}; no other line breaks have been changed
         and the \lstinline!\end{myenv}! statement has \emph{not} received indentation (as
         intended);
   \item in \cref{lst:env-mlb-mod8} a line break has been added at the point denoted by
         $\EndFinishesWithLineBreak$ in \vref{lst:env-mlb1-tex}.
  \end{itemize}

  Let's now change each of the \texttt{1} values in \cref{lst:env-mlb7,lst:env-mlb8} so
  that they are $2$ and save them into \texttt{env-mlb9.yaml} and \texttt{env-mlb10.yaml}
  respectively (see \cref{lst:env-mlb9,lst:env-mlb10}). \index{poly-switches!adding
  comments and then line breaks: set to 2}

  \begin{minipage}{.49\textwidth}
   \cmhlistingsfromfile[style=yaml-LST]{demonstrations/env-mlb9.yaml}[MLB-TCB]{\texttt{env-mlb9.yaml}}{lst:env-mlb9}
  \end{minipage}
  \hfill
  \begin{minipage}{.49\textwidth}
   \cmhlistingsfromfile[style=yaml-LST]{demonstrations/env-mlb10.yaml}[MLB-TCB]{\texttt{env-mlb10.yaml}}{lst:env-mlb10}
  \end{minipage}

  Upon running commands analogous to the above, we obtain
  \cref{lst:env-mlb-mod9,lst:env-mlb-mod10}.

  \begin{widepage}
   \begin{minipage}{.43\linewidth}
    \cmhlistingsfromfile{demonstrations/env-mlb-mod9.tex}{\texttt{env-mlb.tex} using \cref{lst:env-mlb9}}{lst:env-mlb-mod9}
   \end{minipage}
   \hfill
   \begin{minipage}{.56\linewidth}
    \cmhlistingsfromfile{demonstrations/env-mlb-mod10.tex}{\texttt{env-mlb.tex} using \cref{lst:env-mlb10}}{lst:env-mlb-mod10}
   \end{minipage}
  \end{widepage}

  Note that line breaks have been added as in \cref{lst:env-mlb-mod7,lst:env-mlb-mod8}, but
  this time a comment symbol has been added before adding the line break; in both cases,
  trailing horizontal space has been stripped before doing so.

  Let's \announce{2017-08-21}{demonstration of blank line poly-switch (3)} now change each
  of the \texttt{1} values in \cref{lst:env-mlb7,lst:env-mlb8} so that they are $3$ and
  save them into \texttt{env-mlb11.yaml} and \texttt{env-mlb12.yaml} respectively (see
  \cref{lst:env-mlb11,lst:env-mlb12}). \index{poly-switches!adding blank lines: set to 3}%

  \begin{minipage}{.49\textwidth}
   \cmhlistingsfromfile[style=yaml-LST]{demonstrations/env-mlb11.yaml}[MLB-TCB]{\texttt{env-mlb11.yaml}}{lst:env-mlb11}
  \end{minipage}
  \hfill
  \begin{minipage}{.49\textwidth}
   \cmhlistingsfromfile[style=yaml-LST]{demonstrations/env-mlb12.yaml}[MLB-TCB]{\texttt{env-mlb12.yaml}}{lst:env-mlb12}
  \end{minipage}

  Upon running commands analogous to the above, we obtain
  \cref{lst:env-mlb-mod11,lst:env-mlb-mod12}.

  \begin{widepage}
   \begin{minipage}{.42\linewidth}
    \cmhlistingsfromfile{demonstrations/env-mlb-mod11.tex}{\texttt{env-mlb.tex} using \cref{lst:env-mlb11}}{lst:env-mlb-mod11}
   \end{minipage}
   \hfill
   \begin{minipage}{.57\linewidth}
    \cmhlistingsfromfile{demonstrations/env-mlb-mod12.tex}{\texttt{env-mlb.tex} using \cref{lst:env-mlb12}}{lst:env-mlb-mod12}
   \end{minipage}
  \end{widepage}

  Note that line breaks have been added as in \cref{lst:env-mlb-mod7,lst:env-mlb-mod8}, and
  that a \emph{blank line} has been added after the line break.

  Let's now change \announce{2019-07-13}{demonstration of new blank line poly-switch} each
  of the \texttt{1} values in \cref{lst:env-mlb11,lst:env-mlb12} so that they are $4$ and
  save them into \texttt{env-end4.yaml} and \texttt{env-end-f4.yaml} respectively (see
  \cref{lst:env-end4,lst:env-end-f4}). \index{poly-switches!adding blank lines (again"!):
  set to 4}%

  \begin{minipage}{.45\textwidth}
   \cmhlistingsfromfile[style=yaml-LST]{demonstrations/env-end4.yaml}[MLB-TCB]{\texttt{env-end4.yaml}}{lst:env-end4}
  \end{minipage}
  \hfill
  \begin{minipage}{.5\textwidth}
   \cmhlistingsfromfile[style=yaml-LST]{demonstrations/env-end-f4.yaml}[MLB-TCB]{\texttt{env-end-f4.yaml}}{lst:env-end-f4}
  \end{minipage}

  We will demonstrate this poly-switch value using the code from \vref{lst:env-mlb1-text}.

  Upon running the commands \index{switches!-l demonstration} \index{switches!-m
  demonstration}
  \begin{commandshell}
latexindent.pl -m env-mlb1.tex -l env-end4.yaml
latexindent.pl -m env-mlb.1tex -l env-end-f4.yaml
\end{commandshell}

  then we receive the respective outputs in \cref{lst:env-mlb1-end4,lst:env-mlb1-end-f4}.

  \begin{cmhtcbraster}[raster column skip=.1\linewidth]
   \cmhlistingsfromfile{demonstrations/env-mlb1-end4.tex}{\texttt{env-mlb1.tex} using \cref{lst:env-end4}}{lst:env-mlb1-end4}
   \cmhlistingsfromfile{demonstrations/env-mlb1-end-f4.tex}{\texttt{env-mlb1.tex} using \cref{lst:env-end-f4}}{lst:env-mlb1-end-f4}
  \end{cmhtcbraster}

  We note in particular that, by design, for this value of the poly-switches:
  \begin{enumerate}
   \item in \cref{lst:env-mlb1-end4} a blank line has been inserted before the \lstinline!\end!
         statement, even though the \lstinline!\end! statement was already on its own line;
   \item in \cref{lst:env-mlb1-end-f4} a blank line has been inserted after the \lstinline!\end!
         statement, even though it already began on its own line.
  \end{enumerate}

 \paragraph{poly-switches 1, 2, and 3 only add line breaks when necessary}
  If you ask \texttt{latexindent.pl} to add a line break (possibly with a comment) using a
  poly-switch value of $1$ (or $2$ or $3$), it will only do so if necessary. For example,
  if you process the file in \vref{lst:mlb2} using poly-switch values of 1, 2, or 3, it
  will be left unchanged.

  \begin{minipage}{.45\linewidth}
   \cmhlistingsfromfile{demonstrations/env-mlb2.tex}{\texttt{env-mlb2.tex}}{lst:mlb2}
  \end{minipage}
  \hfill
  \begin{minipage}{.45\linewidth}
   \cmhlistingsfromfile{demonstrations/env-mlb3.tex}{\texttt{env-mlb3.tex}}{lst:mlb3}
  \end{minipage}

  Setting the poly-switches to a value of $4$ instructs \texttt{latexindent.pl} to add a
  line break even if the \emph{<part of thing>} is already on its own line; see
  \cref{lst:env-mlb1-beg4,lst:env-mlb1-body4} and
  \cref{lst:env-mlb1-end4,lst:env-mlb1-end-f4}.

  In contrast, the output from processing the file in \cref{lst:mlb3} will vary depending
  on the poly-switches used; in \cref{lst:env-mlb3-mod2} you'll see that the comment symbol
  after the \lstinline!\begin{myenv}! has been moved to the next line, as
  \texttt{BodyStartsOnOwnLine} is set to \texttt{1}. In \cref{lst:env-mlb3-mod4} you'll see
  that the comment has been accounted for correctly because \texttt{BodyStartsOnOwnLine}
  has been set to \texttt{2}, and the comment symbol has \emph{not} been moved to its own
  line. You're encouraged to experiment with \cref{lst:mlb3} and by setting the other
  poly-switches considered so far to \texttt{2} in turn.

  \begin{cmhtcbraster}[raster column skip=.1\linewidth]
   \cmhlistingsfromfile{demonstrations/env-mlb3-mod2.tex}{\texttt{env-mlb3.tex} using \vref{lst:env-mlb2}}{lst:env-mlb3-mod2}
   \cmhlistingsfromfile{demonstrations/env-mlb3-mod4.tex}{\texttt{env-mlb3.tex} using \vref{lst:env-mlb4}}{lst:env-mlb3-mod4}
  \end{cmhtcbraster}

  The details of the discussion in this section have concerned \emph{global} poly-switches
  in the \texttt{environments} field; each switch can also be specified on a
  \emph{per-name} basis, which would take priority over the global values; with reference
  to \vref{lst:environments-mlb}, an example is shown for the \texttt{equation*}
  environment.

 \paragraph{Removing line breaks (poly-switches set to $-1$)}
  Setting poly-switches to $-1$ tells \texttt{latexindent.pl} to remove line breaks of the
  \emph{<part of the thing>}, if necessary. We will consider the example code given in
  \cref{lst:mlb4}, noting in particular the positions of the line break highlighters,
  $\BeginStartsOnOwnLine$, $\BodyStartsOnOwnLine$, $\EndStartsOnOwnLine$ and
  $\EndFinishesWithLineBreak$, together with the associated YAML files in
  \crefrange{lst:env-mlb13}{lst:env-mlb16}. \index{poly-switches!removing line breaks: set
  to -1}

  \begin{minipage}{.45\linewidth}
   \begin{cmhlistings}[style=tcblatex,escapeinside={(*@}{@*)}]{\texttt{env-mlb4.tex}}{lst:mlb4}
before words(*@$\BeginStartsOnOwnLine$@*)
\begin{myenv}(*@$\BodyStartsOnOwnLine$@*)
body of myenv(*@$\EndStartsOnOwnLine$@*)
\end{myenv}(*@$\EndFinishesWithLineBreak$@*)
after words
\end{cmhlistings}
  \end{minipage}%
  \hfill
  \begin{minipage}{.51\textwidth}
   \cmhlistingsfromfile[style=yaml-LST]{demonstrations/env-mlb13.yaml}[MLB-TCB]{\texttt{env-mlb13.yaml}}{lst:env-mlb13}

   \cmhlistingsfromfile[style=yaml-LST]{demonstrations/env-mlb14.yaml}[MLB-TCB]{\texttt{env-mlb14.yaml}}{lst:env-mlb14}

   \cmhlistingsfromfile[style=yaml-LST]{demonstrations/env-mlb15.yaml}[MLB-TCB]{\texttt{env-mlb15.yaml}}{lst:env-mlb15}

   \cmhlistingsfromfile[style=yaml-LST]{demonstrations/env-mlb16.yaml}[MLB-TCB]{\texttt{env-mlb16.yaml}}{lst:env-mlb16}
  \end{minipage}

  After running the commands \index{switches!-l demonstration} \index{switches!-m
  demonstration}
  \begin{commandshell}
latexindent.pl -m env-mlb4.tex -l env-mlb13.yaml
latexindent.pl -m env-mlb4.tex -l env-mlb14.yaml
latexindent.pl -m env-mlb4.tex -l env-mlb15.yaml
latexindent.pl -m env-mlb4.tex -l env-mlb16.yaml
\end{commandshell}

  we obtain the respective output in \crefrange{lst:env-mlb4-mod13}{lst:env-mlb4-mod16}.

  \begin{minipage}{.45\linewidth}
   \cmhlistingsfromfile{demonstrations/env-mlb4-mod13.tex}{\texttt{env-mlb4.tex} using \cref{lst:env-mlb13}}{lst:env-mlb4-mod13}
  \end{minipage}
  \hfill
  \begin{minipage}{.45\linewidth}
   \cmhlistingsfromfile{demonstrations/env-mlb4-mod14.tex}{\texttt{env-mlb4.tex} using \cref{lst:env-mlb14}}{lst:env-mlb4-mod14}
  \end{minipage}

  \begin{minipage}{.45\linewidth}
   \cmhlistingsfromfile{demonstrations/env-mlb4-mod15.tex}{\texttt{env-mlb4.tex} using \cref{lst:env-mlb15}}{lst:env-mlb4-mod15}
  \end{minipage}
  \hfill
  \begin{minipage}{.45\linewidth}
   \cmhlistingsfromfile{demonstrations/env-mlb4-mod16.tex}{\texttt{env-mlb4.tex} using \cref{lst:env-mlb16}}{lst:env-mlb4-mod16}
  \end{minipage}

  Notice that in:
  \begin{itemize}
   \item \cref{lst:env-mlb4-mod13} the line break denoted by $\BeginStartsOnOwnLine$ in
         \cref{lst:mlb4} has been removed;
   \item \cref{lst:env-mlb4-mod14} the line break denoted by $\BodyStartsOnOwnLine$ in
         \cref{lst:mlb4} has been removed;
   \item \cref{lst:env-mlb4-mod15} the line break denoted by $\EndStartsOnOwnLine$ in
         \cref{lst:mlb4} has been removed;
   \item \cref{lst:env-mlb4-mod16} the line break denoted by $\EndFinishesWithLineBreak$ in
         \cref{lst:mlb4} has been removed.
  \end{itemize}
  We examined each of these cases separately for clarity of explanation, but you can
  combine all of the YAML settings in \crefrange{lst:env-mlb13}{lst:env-mlb16} into one
  file; alternatively, you could tell \texttt{latexindent.pl} to load them all by using the
  following command, for example \index{switches!-l demonstration} \index{switches!-m
  demonstration}
  \begin{widepage}
   \begin{commandshell}
latexindent.pl -m env-mlb4.tex -l env-mlb13.yaml,env-mlb14.yaml,env-mlb15.yaml,env-mlb16.yaml
\end{commandshell}
  \end{widepage}
  which gives the output in \vref{lst:env-mlb1-tex}.

 \paragraph{About trailing horizontal space}
  Recall that on \cpageref{yaml:removeTrailingWhitespace} we discussed the YAML field
  \texttt{removeTrailingWhitespace}, and that it has two (binary) switches to determine if
  horizontal space should be removed \texttt{beforeProcessing} and
  \texttt{afterProcessing}. The \texttt{beforeProcessing} is particularly relevant when
  considering the \texttt{-m} switch; let's consider the file shown in \cref{lst:mlb5},
  which highlights trailing spaces.

  \begin{cmhtcbraster}
   \begin{cmhlistings}[style=tcblatex,showspaces=true,escapeinside={(*@}{@*)}]{\texttt{env-mlb5.tex}}{lst:mlb5}
before words   (*@$\BeginStartsOnOwnLine$@*) 
\begin{myenv}           (*@$\BodyStartsOnOwnLine$@*)
body of myenv      (*@$\EndStartsOnOwnLine$@*) 
\end{myenv}     (*@$\EndFinishesWithLineBreak$@*)
after words
\end{cmhlistings}
   \cmhlistingsfromfile[style=yaml-LST]{demonstrations/removeTWS-before.yaml}[yaml-TCB]{\texttt{removeTWS-before.yaml}}{lst:removeTWS-before}
  \end{cmhtcbraster}

  The output from the following commands \index{switches!-l demonstration}
  \index{switches!-m demonstration}
  \begin{widepage}
   \begin{commandshell}
latexindent.pl -m env-mlb5.tex -l env-mlb13.yaml,env-mlb14.yaml,env-mlb15.yaml,env-mlb16.yaml
latexindent.pl -m env-mlb5.tex -l env-mlb13.yaml,env-mlb14.yaml,env-mlb15.yaml,env-mlb16.yaml,removeTWS-before.yaml
\end{commandshell}
  \end{widepage}
  is shown, respectively, in \cref{lst:env-mlb5-modAll,lst:env-mlb5-modAll-remove-WS}; note
  that the trailing horizontal white space has been preserved (by default) in
  \cref{lst:env-mlb5-modAll}, while in \cref{lst:env-mlb5-modAll-remove-WS}, it has been
  removed using the switch specified in \cref{lst:removeTWS-before}.

  \begin{widepage}
   \cmhlistingsfromfile[showspaces=true]{demonstrations/env-mlb5-modAll.tex}{\texttt{env-mlb5.tex} using \crefrange{lst:env-mlb4-mod13}{lst:env-mlb4-mod16}}{lst:env-mlb5-modAll}

   \cmhlistingsfromfile[showspaces=true]{demonstrations/env-mlb5-modAll-remove-WS.tex}{\texttt{env-mlb5.tex} using \crefrange{lst:env-mlb4-mod13}{lst:env-mlb4-mod16} \emph{and} \cref{lst:removeTWS-before}}{lst:env-mlb5-modAll-remove-WS}
  \end{widepage}

 \paragraph{poly-switch line break removal and blank lines}
  Now let's consider the file in \cref{lst:mlb6}, which contains blank lines.
  \index{poly-switches!blank lines}

  \begin{cmhtcbraster}
   \begin{cmhlistings}[style=tcblatex,escapeinside={(*@}{@*)}]{\texttt{env-mlb6.tex}}{lst:mlb6}
before words(*@$\BeginStartsOnOwnLine$@*)


\begin{myenv}(*@$\BodyStartsOnOwnLine$@*)


body of myenv(*@$\EndStartsOnOwnLine$@*)


\end{myenv}(*@$\EndFinishesWithLineBreak$@*)

after words
\end{cmhlistings}
   \cmhlistingsfromfile[style=yaml-LST]{demonstrations/UnpreserveBlankLines.yaml}[MLB-TCB]{\texttt{UnpreserveBlankLines.yaml}}{lst:UnpreserveBlankLines}
  \end{cmhtcbraster}

  Upon running the following commands \index{switches!-l demonstration} \index{switches!-m
  demonstration}
  \begin{widepage}
   \begin{commandshell}
latexindent.pl -m env-mlb6.tex -l env-mlb13.yaml,env-mlb14.yaml,env-mlb15.yaml,env-mlb16.yaml
latexindent.pl -m env-mlb6.tex -l env-mlb13.yaml,env-mlb14.yaml,env-mlb15.yaml,env-mlb16.yaml,UnpreserveBlankLines.yaml
\end{commandshell}
  \end{widepage}
  we receive the respective outputs in
  \cref{lst:env-mlb6-modAll,lst:env-mlb6-modAll-un-Preserve-Blank-Lines}. In
  \cref{lst:env-mlb6-modAll} we see that the multiple blank lines have each been condensed
  into one blank line, but that blank lines have \emph{not} been removed by the
  poly-switches -- this is because, by default, \texttt{preserveBlankLines} is set to
  \texttt{1}. By contrast, in \cref{lst:env-mlb6-modAll-un-Preserve-Blank-Lines}, we have
  allowed the poly-switches to remove blank lines because, in
  \cref{lst:UnpreserveBlankLines}, we have set \texttt{preserveBlankLines} to \texttt{0}.

  \begin{cmhtcbraster}[ raster left skip=-3.5cm,
    raster right skip=-2cm,
    raster force size=false,
    raster column 1/.style={add to width=-.2\textwidth},
    raster column 2/.style={add to width=.2\textwidth},
    raster column skip=.06\linewidth]
   \cmhlistingsfromfile{demonstrations/env-mlb6-modAll.tex}{\texttt{env-mlb6.tex} using \crefrange{lst:env-mlb4-mod13}{lst:env-mlb4-mod16}}{lst:env-mlb6-modAll}
   \cmhlistingsfromfile{demonstrations/env-mlb6-modAll-un-Preserve-Blank-Lines.tex}{\texttt{env-mlb6.tex} using \crefrange{lst:env-mlb4-mod13}{lst:env-mlb4-mod16} \emph{and} \cref{lst:UnpreserveBlankLines}}{lst:env-mlb6-modAll-un-Preserve-Blank-Lines}
  \end{cmhtcbraster}

  We can explore this further using the blank-line poly-switch value of $3$; let's use the
  file given in \cref{lst:env-mlb7-tex}.

  \cmhlistingsfromfile{demonstrations/env-mlb7.tex}{\texttt{env-mlb7.tex}}{lst:env-mlb7-tex}

  Upon running the following commands \index{switches!-l demonstration} \index{switches!-m
  demonstration}
  \begin{commandshell}
latexindent.pl -m env-mlb7.tex -l env-mlb12.yaml,env-mlb13.yaml
latexindent.pl -m env-mlb7.tex -l env-mlb13.yaml,env-mlb14.yaml,UnpreserveBlankLines.yaml
\end{commandshell}
  we receive the outputs given in \cref{lst:env-mlb7-preserve,lst:env-mlb7-no-preserve}.

  \cmhlistingsfromfile{demonstrations/env-mlb7-preserve.tex}{\texttt{env-mlb7-preserve.tex}}{lst:env-mlb7-preserve}
  \cmhlistingsfromfile{demonstrations/env-mlb7-no-preserve.tex}{\texttt{env-mlb7-no-preserve.tex}}{lst:env-mlb7-no-preserve}

  Notice that in:
  \begin{itemize}
   \item \cref{lst:env-mlb7-preserve} that \lstinline!\end{one}! has added a blank line,
         because of the value of \texttt{EndFinishesWithLineBreak} in \vref{lst:env-mlb12}, and
         even though the line break ahead of \lstinline!\begin{two}! should have been removed
         (because of \texttt{BeginStartsOnOwnLine} in \vref{lst:env-mlb13}), the blank line has
         been preserved by default;
   \item \cref{lst:env-mlb7-no-preserve}, by contrast, has had the additional line-break removed,
         because of the settings in \cref{lst:UnpreserveBlankLines}.
  \end{itemize}

\subsubsection{Poly-switches for double back slash}\label{subsec:dbs}
 With reference to \texttt{lookForAlignDelims} (see \vref{lst:aligndelims:basic})
 \announce{2019-07-13}{poly-switch for double back slash} you can specify poly-switches to
 dictate the line-break behaviour of double back slashes in environments
 (\vref{lst:tabularafter:basic}), commands (\vref{lst:matrixafter}), or special code
 blocks (\vref{lst:specialafter}). Note that for these poly-switches to take effect, the
 name of the code block must necessarily be specified within \texttt{lookForAlignDelims}
 (\vref{lst:aligndelims:basic}); we will demonstrate this in what follows.
 \index{delimiters!poly-switches for double back slash} \index{modifying linebreaks!
 surrounding double back slash} \index{poly-switches!for double back slash (delimiters)}%

 Consider the code given in \cref{lst:dbs-demo}.
 \begin{cmhlistings}[style=tcblatex,escapeinside={(*@}{@*)}]{\texttt{tabular3.tex}}{lst:dbs-demo}
\begin{tabular}{cc}
 1 & 2 (*@$\ElseStartsOnOwnLine$@*)\\(*@$\ElseFinishesWithLineBreak$@*) 3 & 4 (*@$\ElseStartsOnOwnLine$@*)\\(*@$\ElseFinishesWithLineBreak$@*)
\end{tabular}
\end{cmhlistings}
 Referencing \cref{lst:dbs-demo}:
 \begin{itemize}
  \item \texttt{DBS} stands for \emph{double back slash};
  \item line breaks ahead of the double back slash are annotated by $\ElseStartsOnOwnLine$, and
        are controlled by \texttt{DBSStartsOnOwnLine};
  \item line breaks after the double back slash are annotated by $\ElseFinishesWithLineBreak$,
        and are controlled by \texttt{DBSFinishesWithLineBreak}.
 \end{itemize}

 Let's explore each of these in turn.

 \paragraph{Double back slash starts on own line}
  We explore \texttt{DBSStartsOnOwnLine} ($\ElseStartsOnOwnLine$ in \cref{lst:dbs-demo});
  starting with the code in \cref{lst:dbs-demo}, together with the YAML files given in
  \cref{lst:DBS1} and \cref{lst:DBS2} and running the following commands \index{switches!-l
  demonstration} \index{switches!-m demonstration}
  \begin{commandshell}
latexindent.pl -m tabular3.tex -l DBS1.yaml
latexindent.pl -m tabular3.tex -l DBS2.yaml
\end{commandshell}
  then we receive the respective output given in \cref{lst:tabular3-DBS1} and
  \cref{lst:tabular3-DBS2}.

  \begin{cmhtcbraster}[raster column skip=.01\linewidth]
   \cmhlistingsfromfile{demonstrations/tabular3-mod1.tex}{\texttt{tabular3.tex} using \cref{lst:DBS1}}{lst:tabular3-DBS1}
   \cmhlistingsfromfile[style=yaml-LST]{demonstrations/DBS1.yaml}[MLB-TCB]{\texttt{DBS1.yaml}}{lst:DBS1}
  \end{cmhtcbraster}

  \begin{cmhtcbraster}[raster column skip=.01\linewidth]
   \cmhlistingsfromfile{demonstrations/tabular3-mod2.tex}{\texttt{tabular3.tex} using \cref{lst:DBS2}}{lst:tabular3-DBS2}
   \cmhlistingsfromfile[style=yaml-LST]{demonstrations/DBS2.yaml}[MLB-TCB]{\texttt{DBS2.yaml}}{lst:DBS2}
  \end{cmhtcbraster}

  We note that
  \begin{itemize}
   \item \cref{lst:DBS1} specifies \texttt{DBSStartsOnOwnLine} for
         \emph{every} environment (that is within \texttt{lookForAlignDelims},
         \vref{lst:aligndelims:advanced});
         the double back slashes from \cref{lst:dbs-demo} have been moved to their own line in
         \cref{lst:tabular3-DBS1};
   \item \cref{lst:DBS2} specifies \texttt{DBSStartsOnOwnLine} on a
         \emph{per-name} basis for \texttt{tabular} (that is within \texttt{lookForAlignDelims},
         \vref{lst:aligndelims:advanced});
         the double back slashes from \cref{lst:dbs-demo} have been moved to their own line in
         \cref{lst:tabular3-DBS2}, having added comment symbols before moving them.
  \end{itemize}

 \paragraph{Double back slash finishes with line break}
  Let's now explore \texttt{DBSFinishesWithLineBreak} ($\ElseFinishesWithLineBreak$ in
  \cref{lst:dbs-demo}); starting with the code in \cref{lst:dbs-demo}, together with the
  YAML files given in \cref{lst:DBS3} and \cref{lst:DBS4} and running the following
  commands \index{poly-switches!for double back slash (delimiters)} \index{switches!-l
  demonstration} \index{switches!-m demonstration}
  \begin{commandshell}
latexindent.pl -m tabular3.tex -l DBS3.yaml
latexindent.pl -m tabular3.tex -l DBS4.yaml
\end{commandshell}
  then we receive the respective output given in \cref{lst:tabular3-DBS3} and
  \cref{lst:tabular3-DBS4}.

  \begin{cmhtcbraster}[raster column skip=.01\linewidth]
   \cmhlistingsfromfile{demonstrations/tabular3-mod3.tex}{\texttt{tabular3.tex} using \cref{lst:DBS3}}{lst:tabular3-DBS3}
   \cmhlistingsfromfile[style=yaml-LST]{demonstrations/DBS3.yaml}[MLB-TCB]{\texttt{DBS3.yaml}}{lst:DBS3}
  \end{cmhtcbraster}

  \begin{cmhtcbraster}[raster column skip=.01\linewidth]
   \cmhlistingsfromfile{demonstrations/tabular3-mod4.tex}{\texttt{tabular3.tex} using \cref{lst:DBS4}}{lst:tabular3-DBS4}
   \cmhlistingsfromfile[style=yaml-LST]{demonstrations/DBS4.yaml}[MLB-TCB]{\texttt{DBS4.yaml}}{lst:DBS4}
  \end{cmhtcbraster}

  We note that
  \begin{itemize}
   \item \cref{lst:DBS3} specifies \texttt{DBSFinishesWithLineBreak} for
         \emph{every} environment (that is within \texttt{lookForAlignDelims},
         \vref{lst:aligndelims:advanced});
         the code following the double back slashes from \cref{lst:dbs-demo} has been moved to
         their own line in \cref{lst:tabular3-DBS3};
   \item \cref{lst:DBS4} specifies \texttt{DBSFinishesWithLineBreak} on a
         \emph{per-name} basis for \texttt{tabular} (that is within \texttt{lookForAlignDelims},
         \vref{lst:aligndelims:advanced});
         the first double back slashes from \cref{lst:dbs-demo} have moved code following them to
         their own line in \cref{lst:tabular3-DBS4}, having added comment symbols before moving
         them; the final double back slashes have \emph{not} added a line break as they are at the
         end of the body within the code block.
  \end{itemize}

 \paragraph{Double back slash poly-switches for specialBeginEnd}
  Let's explore the double back slash poly-switches for code blocks within
  \texttt{specialBeginEnd} code blocks (\vref{lst:specialBeginEnd}); we begin with the code
  within \cref{lst:special4}. \index{specialBeginEnd!double backslash poly-switch
  demonstration} \index{poly-switches!double backslash} \index{poly-switches!for double
  back slash (delimiters)} \index{specialBeginEnd!lookForAlignDelims} \index{delimiters}
  \index{linebreaks!summary of poly-switches}

  \cmhlistingsfromfile{demonstrations/special4.tex}{\texttt{special4.tex}}{lst:special4}

  Upon using the YAML settings in \cref{lst:DBS5}, and running the command
  \index{switches!-l demonstration} \index{switches!-m demonstration}
  \begin{commandshell}
latexindent.pl -m special4.tex -l DBS5.yaml
\end{commandshell}
  then we receive the output given in \cref{lst:special4-DBS5}. \index{delimiters!with
  specialBeginEnd and the -m switch}

  \begin{cmhtcbraster}[
    raster force size=false,
    raster column 1/.style={add to width=-.1\textwidth},
    raster column skip=.06\linewidth]
   \cmhlistingsfromfile{demonstrations/special4-mod5.tex}{\texttt{special4.tex} using \cref{lst:DBS5}}{lst:special4-DBS5}
   \cmhlistingsfromfile[style=yaml-LST]{demonstrations/DBS5.yaml}[MLB-TCB,width=0.6\textwidth]{\texttt{DBS5.yaml}}{lst:DBS5}
  \end{cmhtcbraster}

  There are a few things to note:
  \begin{itemize}
   \item in \cref{lst:DBS5} we have specified \texttt{cmhMath} within \texttt{lookForAlignDelims};
         without this, the double back slash poly-switches would be ignored for this code block;
   \item the \texttt{DBSFinishesWithLineBreak} poly-switch has controlled the line breaks
         following the double back slashes;
   \item the \texttt{SpecialEndStartsOnOwnLine} poly-switch has controlled the addition of a
         comment symbol, followed by a line break, as it is set to a value of 2.
  \end{itemize}

 \paragraph{Double back slash poly-switches for optional and mandatory arguments}
  For clarity, we provide a demonstration of controlling the double back slash
  poly-switches for optional and mandatory arguments. We begin with the code in
  \cref{lst:mycommand2}. \index{poly-switches!for double back slash (delimiters)}

  \cmhlistingsfromfile{demonstrations/mycommand2.tex}{\texttt{mycommand2.tex}}{lst:mycommand2}

  Upon using the YAML settings in \cref{lst:DBS6,lst:DBS7}, and running the command
  \index{switches!-l demonstration} \index{switches!-m demonstration}
  \begin{commandshell}
latexindent.pl -m mycommand2.tex -l DBS6.yaml
latexindent.pl -m mycommand2.tex -l DBS7.yaml
\end{commandshell}
  then we receive the output given in \cref{lst:mycommand2-DBS6,lst:mycommand2-DBS7}.

  \begin{cmhtcbraster}[
    raster force size=false,
    raster column 1/.style={add to width=-.1\textwidth},
    raster column skip=.03\linewidth]
   \cmhlistingsfromfile{demonstrations/mycommand2-mod6.tex}{\texttt{mycommand2.tex} using \cref{lst:DBS6}}{lst:mycommand2-DBS6}
   \cmhlistingsfromfile[style=yaml-LST]{demonstrations/DBS6.yaml}[MLB-TCB,width=0.6\textwidth]{\texttt{DBS6.yaml}}{lst:DBS6}
  \end{cmhtcbraster}

  \begin{cmhtcbraster}[
    raster force size=false,
    raster column 1/.style={add to width=-.1\textwidth},
    raster column skip=.03\linewidth]
   \cmhlistingsfromfile{demonstrations/mycommand2-mod7.tex}{\texttt{mycommand2.tex} using \cref{lst:DBS7}}{lst:mycommand2-DBS7}
   \cmhlistingsfromfile[style=yaml-LST]{demonstrations/DBS7.yaml}[MLB-TCB,width=0.6\textwidth]{\texttt{DBS7.yaml}}{lst:DBS7}
  \end{cmhtcbraster}

 \paragraph{Double back slash optional square brackets}
  The pattern matching for the double back slash will also, optionally, allow trailing
  square brackets that contain a measurement of vertical spacing, for example
  \lstinline!\\[3pt]!. \index{poly-switches!for double back slash (delimiters)}

  For example, beginning with the code in \cref{lst:pmatrix3}

  \cmhlistingsfromfile{demonstrations/pmatrix3.tex}{\texttt{pmatrix3.tex}}{lst:pmatrix3}

  and running the following command, using \cref{lst:DBS3}, \index{switches!-l
  demonstration} \index{switches!-m demonstration}
  \begin{commandshell}
latexindent.pl -m pmatrix3.tex -l DBS3.yaml
\end{commandshell}
  then we receive the output given in \cref{lst:pmatrix3-DBS3}.

  \cmhlistingsfromfile{demonstrations/pmatrix3-mod3.tex}{\texttt{pmatrix3.tex} using \cref{lst:DBS3}}{lst:pmatrix3-DBS3}

  You can customise the pattern for the double back slash by exploring the \emph{fine
  tuning} field detailed in \vref{lst:fineTuning}.

\subsubsection{Poly-switches for other code blocks}
 Rather than repeat the examples shown for the environment code blocks (in
 \vref{sec:modifylinebreaks-environments}), we choose to detail the poly-switches for all
 other code blocks in \cref{tab:poly-switch-mapping}; note that each and every one of
 these poly-switches is \emph{off by default}, i.e, set to \texttt{0}.

 Note also that, by design, line breaks involving, \texttt{filecontents} and
 `comment-marked' code blocks (\vref{lst:alignmentmarkup}) can \emph{not} be modified
 using \texttt{latexindent.pl}. \announce{2019-05-05}*{verbatim poly-switch} However,
 there are two poly-switches available for \texttt{verbatim} code blocks: environments
 (\vref{lst:verbatimEnvironments}), commands (\vref{lst:verbatimCommands}) and
 \texttt{specialBeginEnd} (\vref{lst:special-verb1-yaml}).
 \index{specialBeginEnd!poly-switch summary} \index{verbatim!poly-switch summary}
 \index{poly-switches!summary of all poly-switches}%

 \clearpage
 \begin{longtable}{llll}
  \caption{Poly-switch mappings for all code-block types}\label{tab:poly-switch-mapping}                                                                                                                                                   \\
  \toprule
  Code block                                             & Sample                                                            & \multicolumn{2}{c}{Poly-switch mapping}                                                                     \\
  \midrule
  environment                                            & \verb!before words!$\BeginStartsOnOwnLine$                        & $\BeginStartsOnOwnLine$                 & BeginStartsOnOwnLine                                              \\
                                                         & \verb!\begin{myenv}!$\BodyStartsOnOwnLine$                        & $\BodyStartsOnOwnLine$                  & BodyStartsOnOwnLine                                               \\
                                                         & \verb!body of myenv!$\EndStartsOnOwnLine$                         & $\EndStartsOnOwnLine$                   & EndStartsOnOwnLine                                                \\
                                                         & \verb!\end{myenv}!$\EndFinishesWithLineBreak$                     & $\EndFinishesWithLineBreak$             & EndFinishesWithLineBreak                                          \\
                                                         & \verb!after words!                                                &                                         &                                                                   \\
  \cmidrule{2-4}
  ifelsefi                                               & \verb!before words!$\BeginStartsOnOwnLine$                        & $\BeginStartsOnOwnLine$                 & IfStartsOnOwnLine                                                 \\
                                                         & \verb!\if...!$\BodyStartsOnOwnLine$                               & $\BodyStartsOnOwnLine$                  & BodyStartsOnOwnLine                                               \\
                                                         & \verb!body of if/or statement!$\OrStartsOnOwnLine$                & $\OrStartsOnOwnLine$                    & OrStartsOnOwnLine                                                 %
  \announce{2018-04-27}{new ifElseFi code block poly-switches}                                                                                                                                                                             \\
                                                         & \verb!\or!$\OrFinishesWithLineBreak$                              & $\OrFinishesWithLineBreak$              & OrFinishesWithLineBreak                                           \\
                                                         & \verb!body of if/or statement!$\ElseStartsOnOwnLine$              & $\ElseStartsOnOwnLine$                  & ElseStartsOnOwnLine                                               \\
                                                         & \verb!\else!$\ElseFinishesWithLineBreak$                          & $\ElseFinishesWithLineBreak$            & ElseFinishesWithLineBreak                                         \\
                                                         & \verb!body of else statement!$\EndStartsOnOwnLine$                & $\EndStartsOnOwnLine$                   & FiStartsOnOwnLine                                                 \\
                                                         & \verb!\fi!$\EndFinishesWithLineBreak$                             & $\EndFinishesWithLineBreak$             & FiFinishesWithLineBreak                                           \\
                                                         & \verb!after words!                                                &                                         &                                                                   \\
  \cmidrule{2-4}
  optionalArguments                                      & \verb!...!$\BeginStartsOnOwnLine$                                 & $\BeginStartsOnOwnLine$                 & LSqBStartsOnOwnLine\footnote{LSqB stands for Left Square Bracket} \\
                                                         & \verb![!$\BodyStartsOnOwnLine$                                    & $\BodyStartsOnOwnLine$                  & OptArgBodyStartsOnOwnLine                                         \\
  \announce{2019-07-13}{new comma-related poly-switches} & \verb!value before comma!$\ElseStartsOnOwnLine$,                  & $\ElseStartsOnOwnLine$                  & CommaStartsOnOwnLine                                              \\
                                                         & $\ElseFinishesWithLineBreak$                                      & $\ElseFinishesWithLineBreak$            & CommaFinishesWithLineBreak                                        \\
                                                         & \verb!end of body of opt arg!$\EndStartsOnOwnLine$                & $\EndStartsOnOwnLine$                   & RSqBStartsOnOwnLine                                               \\
                                                         & \verb!]!$\EndFinishesWithLineBreak$                               & $\EndFinishesWithLineBreak$             & RSqBFinishesWithLineBreak                                         \\
                                                         & \verb!...!                                                        &                                         &                                                                   \\
  \cmidrule{2-4}
  mandatoryArguments                                     & \verb!...!$\BeginStartsOnOwnLine$                                 & $\BeginStartsOnOwnLine$                 & LCuBStartsOnOwnLine\footnote{LCuB stands for Left Curly Brace}    \\
                                                         & \verb!{!$\BodyStartsOnOwnLine$                                    & $\BodyStartsOnOwnLine$                  & MandArgBodyStartsOnOwnLine                                        \\
  \announce{2019-07-13}{new comma-related poly-switches} & \verb!value before comma!$\ElseStartsOnOwnLine$,                  & $\ElseStartsOnOwnLine$                  & CommaStartsOnOwnLine                                              \\
                                                         & $\ElseFinishesWithLineBreak$                                      & $\ElseFinishesWithLineBreak$            & CommaFinishesWithLineBreak                                        \\
                                                         & \verb!end of body of mand arg!$\EndStartsOnOwnLine$               & $\EndStartsOnOwnLine$                   & RCuBStartsOnOwnLine                                               \\
                                                         & \verb!}!$\EndFinishesWithLineBreak$                               & $\EndFinishesWithLineBreak$             & RCuBFinishesWithLineBreak                                         \\
                                                         & \verb!...!                                                        &                                         &                                                                   \\
  \cmidrule{2-4}
  commands                                               & \verb!before words!$\BeginStartsOnOwnLine$                        & $\BeginStartsOnOwnLine$                 & CommandStartsOnOwnLine                                            \\
                                                         & \verb!\mycommand!$\BodyStartsOnOwnLine$                           & $\BodyStartsOnOwnLine$                  & CommandNameFinishesWithLineBreak                                  \\
                                                         & $\langle$\itshape{arguments}$\rangle$                             &                                         &                                                                   \\
  \cmidrule{2-4}
  namedGroupingBracesBrackets                            & before words$\BeginStartsOnOwnLine$                               & $\BeginStartsOnOwnLine$                 & NameStartsOnOwnLine                                               \\
                                                         & myname$\BodyStartsOnOwnLine$                                      & $\BodyStartsOnOwnLine$                  & NameFinishesWithLineBreak                                         \\
                                                         & $\langle$\itshape{braces/brackets}$\rangle$                       &                                         &                                                                   \\
  \cmidrule{2-4}
  keyEqualsValuesBraces\newline Brackets                 & before words$\BeginStartsOnOwnLine$                               & $\BeginStartsOnOwnLine$                 & KeyStartsOnOwnLine                                                \\
                                                         & key$\EqualsStartsOnOwnLine$=$\BodyStartsOnOwnLine$                & $\EqualsStartsOnOwnLine$                & EqualsStartsOnOwnLine                                             \\
                                                         & $\langle$\itshape{braces/brackets}$\rangle$                       & $\BodyStartsOnOwnLine$                  & EqualsFinishesWithLineBreak                                       \\
  \cmidrule{2-4}
  items                                                  & before words$\BeginStartsOnOwnLine$                               & $\BeginStartsOnOwnLine$                 & ItemStartsOnOwnLine                                               \\
                                                         & \verb!\item!$\BodyStartsOnOwnLine$                                & $\BodyStartsOnOwnLine$                  & ItemFinishesWithLineBreak                                         \\
                                                         & \verb!...!                                                        &                                         &                                                                   \\
  \cmidrule{2-4}
  specialBeginEnd                                        & before words$\BeginStartsOnOwnLine$                               & $\BeginStartsOnOwnLine$                 & SpecialBeginStartsOnOwnLine                                       \\
                                                         & \verb!\[!$\BodyStartsOnOwnLine$                                   & $\BodyStartsOnOwnLine$                  & SpecialBodyStartsOnOwnLine                                        \\
                                                         & \verb!body of special/middle!$\ElseStartsOnOwnLine$               & $\ElseStartsOnOwnLine$                  & SpecialMiddleStartsOnOwnLine                                      %
  \announce{2018-04-27}{new special code block poly-switches}                                                                                                                                                                              \\
                                                         & \verb!\middle!$\ElseFinishesWithLineBreak$                        & $\ElseFinishesWithLineBreak$            & SpecialMiddleFinishesWithLineBreak                                \\
                                                         & body of special/middle $\EndStartsOnOwnLine$                      & $\EndStartsOnOwnLine$                   & SpecialEndStartsOnOwnLine                                         \\
                                                         & \verb!\]!$\EndFinishesWithLineBreak$                              & $\EndFinishesWithLineBreak$             & SpecialEndFinishesWithLineBreak                                   \\
                                                         & after words                                                       &                                         &                                                                   \\
  \cmidrule{2-4}
  verbatim                                               & before words$\BeginStartsOnOwnLine$\verb!\begin{verbatim}!        & $\BeginStartsOnOwnLine$                 & VerbatimBeginStartsOnOwnLine                                      \\
  \announce{2019-05-05}{verbatim poly-switches}          & body of verbatim \verb!\end{verbatim}!$\EndFinishesWithLineBreak$ & $\EndFinishesWithLineBreak$             & VerbatimEndFinishesWithLineBreak                                  \\
                                                         & after words                                                       &                                         &                                                                   \\
  \bottomrule
 \end{longtable}
\subsubsection{Partnering BodyStartsOnOwnLine with argument-based poly-switches}
 Some poly-switches need to be partnered together; in particular, when line breaks
 involving the \emph{first} argument of a code block need to be accounted for using both
 \texttt{BodyStartsOnOwnLine} (or its equivalent, see \vref{tab:poly-switch-mapping}) and
 \texttt{LCuBStartsOnOwnLine} for mandatory arguments, and \texttt{LSqBStartsOnOwnLine}
 for optional arguments. \index{poly-switches!conflicting partnering}

 Let's begin with the code in \cref{lst:mycommand1} and the YAML settings in
 \cref{lst:mycom-mlb1}; with reference to \vref{tab:poly-switch-mapping}, the key
 \texttt{CommandNameFinishesWithLineBreak} is an alias for \texttt{BodyStartsOnOwnLine}.

 \cmhlistingsfromfile{demonstrations/mycommand1.tex}{\texttt{mycommand1.tex}}{lst:mycommand1}

 Upon running the command \index{switches!-l demonstration} \index{switches!-m
 demonstration}
 \begin{commandshell}
latexindent.pl -m -l=mycom-mlb1.yaml mycommand1.tex
\end{commandshell}
 we obtain \cref{lst:mycommand1-mlb1}; note that the \emph{second} mandatory argument
 beginning brace \lstinline!{! has had its leading line break removed, but that the
 \emph{first} brace has not.

 \begin{cmhtcbraster}[
   raster force size=false,
   raster column 1/.style={add to width=-1cm},
  ]
  \cmhlistingsfromfile{demonstrations/mycommand1-mlb1.tex}{\texttt{mycommand1.tex} using \cref{lst:mycom-mlb1}}{lst:mycommand1-mlb1}
  \cmhlistingsfromfile[style=yaml-LST]{demonstrations/mycom-mlb1.yaml}[MLB-TCB,width=.6\textwidth]{\texttt{mycom-mlb1.yaml}}{lst:mycom-mlb1}
 \end{cmhtcbraster}

 Now let's change the YAML file so that it is as in \cref{lst:mycom-mlb2}; upon running
 the analogous command to that given above, we obtain \cref{lst:mycommand1-mlb2}; both
 beginning braces \lstinline!{! have had their leading line breaks removed.

 \begin{cmhtcbraster}[
   raster force size=false,
   raster column 1/.style={add to width=-1cm},
  ]
  \cmhlistingsfromfile{demonstrations/mycommand1-mlb2.tex}{\texttt{mycommand1.tex} using \cref{lst:mycom-mlb2}}{lst:mycommand1-mlb2}
  \cmhlistingsfromfile[style=yaml-LST]{demonstrations/mycom-mlb2.yaml}[MLB-TCB,width=.6\textwidth]{\texttt{mycom-mlb2.yaml}}{lst:mycom-mlb2}
 \end{cmhtcbraster}

 Now let's change the YAML file so that it is as in \cref{lst:mycom-mlb3}; upon running
 the analogous command to that given above, we obtain \cref{lst:mycommand1-mlb3}.

 \begin{cmhtcbraster}[
   raster force size=false,
   raster column 1/.style={add to width=-1cm},
  ]
  \cmhlistingsfromfile{demonstrations/mycommand1-mlb3.tex}{\texttt{mycommand1.tex} using \cref{lst:mycom-mlb3}}{lst:mycommand1-mlb3}
  \cmhlistingsfromfile[style=yaml-LST]{demonstrations/mycom-mlb3.yaml}[MLB-TCB,width=.6\textwidth]{\texttt{mycom-mlb3.yaml}}{lst:mycom-mlb3}
 \end{cmhtcbraster}

\subsubsection{Conflicting poly-switches: sequential code blocks}
 It is very easy to have conflicting poly-switches; if we use the example from
 \vref{lst:mycommand1}, and consider the YAML settings given in \cref{lst:mycom-mlb4}. The
 output from running \index{poly-switches!conflicting switches} \index{switches!-l
 demonstration} \index{switches!-m demonstration}
 \begin{commandshell}
latexindent.pl -m -l=mycom-mlb4.yaml mycommand1.tex
\end{commandshell}
 is given in \cref{lst:mycom-mlb4}.

 \begin{cmhtcbraster}
  \cmhlistingsfromfile{demonstrations/mycommand1-mlb4.tex}{\texttt{mycommand1.tex} using \cref{lst:mycom-mlb4}}{lst:mycommand1-mlb4}
  \cmhlistingsfromfile[style=yaml-LST]{demonstrations/mycom-mlb4.yaml}[MLB-TCB,width=\linewidth]{\texttt{mycom-mlb4.yaml}}{lst:mycom-mlb4}
 \end{cmhtcbraster}

 Studying \cref{lst:mycom-mlb4}, we see that the two poly-switches are at opposition with
 one another:
 \begin{itemize}
  \item on the one hand, \texttt{LCuBStartsOnOwnLine} should \emph{not} start on its own line (as
        poly-switch is set to $-1$);
  \item on the other hand, \texttt{RCuBFinishesWithLineBreak} \emph{should} finish with a line
        break.
 \end{itemize}
 So, which should win the conflict? As demonstrated in \cref{lst:mycommand1-mlb4}, it is
 clear that \texttt{LCuBStartsOnOwnLine} won this conflict, and the reason is that
 \emph{the second argument was processed after the first} -- in general, the most
 recently-processed code block and associated poly-switch takes priority.

 We can explore this further by considering the YAML settings in \cref{lst:mycom-mlb5};
 upon running the command \index{switches!-l demonstration} \index{switches!-m
 demonstration}
 \begin{commandshell}
latexindent.pl -m -l=mycom-mlb5.yaml mycommand1.tex
\end{commandshell}
 we obtain the output given in \cref{lst:mycommand1-mlb5}.

 \begin{cmhtcbraster}[raster column skip=.1\linewidth]
  \cmhlistingsfromfile{demonstrations/mycommand1-mlb5.tex}{\texttt{mycommand1.tex} using \cref{lst:mycom-mlb5}}{lst:mycommand1-mlb5}
  \cmhlistingsfromfile[style=yaml-LST]{demonstrations/mycom-mlb5.yaml}[MLB-TCB,width=\linewidth]{\texttt{mycom-mlb5.yaml}}{lst:mycom-mlb5}
 \end{cmhtcbraster}

 As previously, the most-recently-processed code block takes priority -- as before, the
 second (i.e, \emph{last}) argument. Exploring this further, we consider the YAML settings
 in \cref{lst:mycom-mlb6}, which give associated output in \cref{lst:mycommand1-mlb6}.

 \begin{cmhtcbraster}[raster column skip=.1\linewidth]
  \cmhlistingsfromfile{demonstrations/mycommand1-mlb6.tex}{\texttt{mycommand1.tex} using \cref{lst:mycom-mlb6}}{lst:mycommand1-mlb6}
  \cmhlistingsfromfile[style=yaml-LST]{demonstrations/mycom-mlb6.yaml}[MLB-TCB,width=\linewidth]{\texttt{mycom-mlb6.yaml}}{lst:mycom-mlb6}
 \end{cmhtcbraster}

 Note that a \lstinline!%! \emph{has} been added to the trailing first \lstinline!}!; this
 is because:
 \begin{itemize}
  \item while processing the \emph{first} argument, the trailing line break has been removed
        (\texttt{RCuBFinishesWithLineBreak} set to $-1$);
  \item while processing the \emph{second} argument, \texttt{latexindent.pl} finds that it does
        \emph{not} begin on its own line, and so because \texttt{LCuBStartsOnOwnLine} is set to
        $2$, it adds a comment, followed by a line break.
 \end{itemize}

\subsubsection{Conflicting poly-switches: nested code blocks}
 Now let's consider an example when nested code blocks have conflicting poly-switches;
 we'll use the code in \cref{lst:nested-env}, noting that it contains nested environments.
 \index{poly-switches!conflicting switches}

 \cmhlistingsfromfile{demonstrations/nested-env.tex}{\texttt{nested-env.tex}}{lst:nested-env}

 Let's use the YAML settings given in \cref{lst:nested-env-mlb1-yaml}, which upon running
 the command \index{switches!-l demonstration} \index{switches!-m demonstration}
 \begin{commandshell}
latexindent.pl -m -l=nested-env-mlb1.yaml nested-env.tex
\end{commandshell}
 gives the output in \cref{lst:nested-env-mlb1}.

 \begin{cmhtcbraster}[raster column skip=.05\linewidth]
  \cmhlistingsfromfile{demonstrations/nested-env-mlb1.tex}{\texttt{nested-env.tex} using \cref{lst:nested-env-mlb1-yaml}}{lst:nested-env-mlb1}
  \cmhlistingsfromfile[style=yaml-LST]{demonstrations/nested-env-mlb1.yaml}[MLB-TCB,width=\linewidth]{\texttt{nested-env-mlb1.yaml}}{lst:nested-env-mlb1-yaml}
 \end{cmhtcbraster}

 In \cref{lst:nested-env-mlb1}, let's first of all note that both environments have
 received the appropriate (default) indentation; secondly, note that the poly-switch
 \texttt{EndStartsOnOwnLine} appears to have won the conflict, as \lstinline!\end{one}!
 has had its leading line break removed.

 To understand it, let's talk about the three basic phases \label{page:phases}of
 \texttt{latexindent.pl}:
 \begin{enumerate}
  \item Phase 1: packing, in which code blocks are replaced with unique ids, working from
        \emph{the inside to the outside}, and then sequentially -- for example, in
        \cref{lst:nested-env}, the \texttt{two} environment is found \emph{before} the
        \texttt{one} environment; if the -m switch is active, then during this phase:
        \begin{itemize}
         \item line breaks at the beginning of the \texttt{body} can be added (if
               \texttt{BodyStartsOnOwnLine} is $1$ or $2$) or removed (if \texttt{BodyStartsOnOwnLine}
               is $-1$);
         \item line breaks at the end of the body can be added (if \texttt{EndStartsOnOwnLine} is $1$ or
               $2$) or removed (if \texttt{EndStartsOnOwnLine} is $-1$);
         \item line breaks after the end statement can be added (if \texttt{EndFinishesWithLineBreak} is
               $1$ or $2$).
        \end{itemize}
  \item Phase 2: indentation, in which white space is added to the begin, body, and end
        statements;
  \item Phase 3: unpacking, in which unique ids are replaced by their \emph{indented} code
        blocks; if the -m switch is active, then during this phase,
        \begin{itemize}
         \item line breaks before \texttt{begin} statements can be added or removed (depending upon
               \texttt{BeginStartsOnOwnLine});
         \item line breaks after \emph{end} statements can be removed but \emph{NOT} added (see
               \texttt{EndFinishesWithLineBreak}).
        \end{itemize}
 \end{enumerate}

 With reference to \cref{lst:nested-env-mlb1}, this means that during Phase 1:
 \begin{itemize}
  \item the \texttt{two} environment is found first, and the line break ahead of the
        \lstinline!\end{two}! statement is removed because \texttt{EndStartsOnOwnLine} is set to
        $-1$. Importantly, because, \emph{at this stage}, \lstinline!\end{two}! \emph{does}
        finish with a line break, \texttt{EndFinishesWithLineBreak} causes no action.
  \item next, the \texttt{one} environment is found; the line break ahead of
        \lstinline!\end{one}! is removed because \texttt{EndStartsOnOwnLine} is set to $-1$.
 \end{itemize}
 The indentation is done in Phase 2; in Phase 3 \emph{there is no option to add a line
 break after the \lstinline!end! statements}. We can justify this by remembering that
 during Phase 3, the \texttt{one} environment will be found and processed first, followed
 by the \texttt{two} environment. If the \texttt{two} environment were to add a line break
 after the \lstinline!\end{two}! statement, then \texttt{latexindent.pl} would have no way
 of knowing how much indentation to add to the subsequent text (in this case,
 \lstinline!\end{one}!).

 We can explore this further using the poly-switches in \cref{lst:nested-env-mlb2}; upon
 running the command \index{switches!-l demonstration} \index{switches!-m demonstration}
 \begin{commandshell}
latexindent.pl -m -l=nested-env-mlb2.yaml nested-env.tex
\end{commandshell}
 we obtain the output given in \cref{lst:nested-env-mlb2-output}.

 \begin{cmhtcbraster}
  \cmhlistingsfromfile{demonstrations/nested-env-mlb2.tex}{\texttt{nested-env.tex} using \cref{lst:nested-env-mlb2}}{lst:nested-env-mlb2-output}
  \cmhlistingsfromfile[style=yaml-LST]{demonstrations/nested-env-mlb2.yaml}[MLB-TCB,width=\linewidth]{\texttt{nested-env-mlb2.yaml}}{lst:nested-env-mlb2}
 \end{cmhtcbraster}

 During Phase 1:
 \begin{itemize}
  \item the \texttt{two} environment is found first, and the line break ahead of the
        \lstinline!\end{two}! statement is not changed because \texttt{EndStartsOnOwnLine} is set
        to $1$. Importantly, because, \emph{at this stage}, \lstinline!\end{two}! \emph{does}
        finish with a line break, \texttt{EndFinishesWithLineBreak} causes no action.
  \item next, the \texttt{one} environment is found; the line break ahead of
        \lstinline!\end{one}! is already present, and no action is needed.
 \end{itemize}
 The indentation is done in Phase 2, and then in Phase 3, the \texttt{one} environment is
 found and processed first, followed by the \texttt{two} environment. \emph{At this
 stage}, the \texttt{two} environment finds \texttt{EndFinishesWithLineBreak} is $-1$, so
 it removes the trailing line break; remember, at this point, \texttt{latexindent.pl} has
 completely finished with the \texttt{one} environment.
