% \iffalse meta-comment
%
% verse.dtx
% Author: Peter Wilson
% Maintainer: Will Robertson (will dot robertson at latex-project dot org)
%         Herries Press
% Copyright 2001--2007 Peter R. Wilson
%
% This work 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: <http://www.latex-project.org/lppl.txt>
%
% This work has the LPPL maintenance status "maintained".
% The Current Maintainer of this work is Will Robertson.
%
% This work consists of the files listed in the README file.
%
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%
% \changes{v1.0}{2001/07/21}{First public release}
% \changes{v1.1}{2001/08/03}{Added patterns for line indents}
% \changes{v1.2}{2001/10/28}{Minor change in verse environment}
% \changes{v2.0}{2002/03/24}{Added numbering}
% \changes{v2.1}{2002/03/28}{Added shorthands for linebreak and end of stanza}
% \changes{v2.2}{2002/07/18}{Added interstanza spacing}
% \changes{v2.21}{2004/03/21}{Made compatible with hangul package}
% \changes{v2.22}{2005/08/22}{Made compatible with hyperref package}
% \changes{v2.3}{2006/01/14}{Added switch for linenumber side}
% \changes{v2.4}{2007/01/10}{Added code to start numbering at a given line}
% \changes{v2.4a}{2009/09/04}{New maintainer (Will Robertson)}
% \changes{v2.4b}{2014/05/10}{Documentation updates}
%
% \def\dtxfile{verse.dtx}
% ^^A \def\fileversion{v1.0}
% ^^A \def\filedate{2001/07/21}
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% \def\fileversion{v2.4a} \def\filedate{2009/09/04}
% \def\fileversion{v2.4b} \def\filedate{2014/05/10}
% \newcommand*{\Lpack}[1]{\textsf {#1}}           ^^A typeset a package
% \newcommand*{\Lopt}[1]{\textsf {#1}}            ^^A typeset an option
% \newcommand*{\file}[1]{\texttt {#1}}            ^^A typeset a file
% \newcommand*{\Lcount}[1]{\textsl {\small#1}}    ^^A typeset a counter
% \newcommand*{\pstyle}[1]{\textsl {#1}}          ^^A typeset a pagestyle
% \newcommand*{\Lenv}[1]{\texttt {#1}}            ^^A typeset an environment
% \newcommand*{\ablankline}{\vspace{\baselineskip}}
%
% \title{Typesetting simple verse with \LaTeX}
%
% \author{
%   Author: Peter Wilson, Herries Press \\
%   Maintainer: Will Robertson \\
%   \large
%   \texttt{http://github.com/wspr/herries-press/}
% }
% \date{\fileversion\qquad\filedate}
% \maketitle
% \begin{abstract}
%    The \Lpack{verse} package provides some aids for the typesetting
% of simple verse.
%
% \end{abstract}
% \tableofcontents
%
% 
%
% \section{Introduction}
%
% The typesetting of a poem should be really be dependent on the
% particular poem. Individual problems do not usually admit of a
% general solution, so this document and code should be used more
% as a guide towards some solutions rather than providing a ready
% made solution for any particular piece of verse.
%
% This manual is typeset according to the conventions of the
% \LaTeX{} \textsc{docstrip} utility which enables the automatic
% extraction of the \LaTeX{} macro source files~\cite{GOOSSENS94}.
%
%    Section~\ref{sec:usc} describes the usage of the \Lpack{verse} 
% package and 
% commented source code is in Section~\ref{sec:code}.
% Colour is used to indicate input and output material; a \colorbox[rgb]{0.97,0.97,1}{blue} background indicates \LaTeX\ input source, and a \colorbox[rgb]{0.97,1,0.97}{green} background shows the corresponding output one should expect.
%
% The doggerel used as illustrative material has been taken 
% from~\cite{RUMOUR}.
%
% \section{Verses in \LaTeX\ \emph{without} this package}
%
% LaTeX provides the |verse| environment which is defined as a particular
% kind of list. Within the environment you use |\\| to end a line
% and a blank line will end a stanza. For example, here is a single
% stanza poem:
% \begin{lstlisting}
% \newcommand{\garden}{
%   I used to love my garden \\
%   But now my love is dead \\
%   For I found a bachelor's button \\
%   In black-eyed Susan's bed.
% }
% \end{lstlisting}
% \newcommand{\garden}{
% I used to love my garden \\
% But now my love is dead \\
% For I found a bachelor's button \\
% In black-eyed Susan's bed.
% }
% When this is typeset as a normal LaTeX paragraph (with no paragraph
% indentation) it looks like:
% \begin{ltxoutput}
% \garden{}
% \end{ltxoutput}
% Typesetting it within \LaTeX's |verse| environment produces:
% \begin{ltxoutput}
% \begin{verse}  
% \garden
% \end{verse}
% \end{ltxoutput}
% The stanza could also be typeset within the |alltt| environment, defined
% in the standard \Lpack{alltt} package, using a normal font and no |\\|
% line endings.
% \begin{lstlisting}
% \begin{alltt}\normalfont
% I used to love my garden 
% But now my love is dead 
% For I found a bachelor's button 
% In black-eyed Susan's bed.
% \end{alltt}\end{lstlisting}
% which produces:
% \begin{ltxoutput}
% \begin{alltt}\catcode\%=9
%\normalfont
%I used to love my garden 
%But now my love is dead 
%For I found a bachelor's button 
%In black-eyed Susan's bed.
% \end{alltt}
% \end{ltxoutput}
% The |alltt| environment is like the |verbatim| environment except that
% you can use LaTeX macros inside it.
%
%    In the |verse| environment long lines will be wrapped and indented
% but in the |alltt| environment there is no indentation. 
%
% Some stanzas have certain lines indented, often alternate ones. To
% typeset stanzas like this you have to add your own spacing. For
% instance:
% \begin{lstlisting}
% \begin{verse}
% There was an old party of Lyme \\
% Who married three wives at one time. \\
% \hspace{2em} When asked: `Why the third?' \\
% \hspace{2em} He replied: `One's absurd, \\
% And bigamy, sir, is a crime.'
% \end{verse}
% \end{lstlisting}
% will be typeset in a verse environment as: 
% \begin{ltxoutput}
% \begin{verse}
% There was an old party of Lyme \\
% Who married three wives at one time. \\
% \hspace{2em} When asked: `Why the third?' \\
% \hspace{2em} He replied: `One's absurd, \\
% And bigamy, sir, is a crime.'
% \end{verse}
% \end{ltxoutput}
% Using the |alltt| environment you can put in the spacing via ordinary
% spaces. That is, this
% \begin{lstlisting}
% \begin{alltt}\normalfont
% There was an old party of Lyme
% Who married three wives at one time.
%       When asked: `Why the third?' 
%       He replied: `One's absurd, 
% And bigamy, sir, is a crime.'
% \end{alltt}
% \end{lstlisting}
% is typeset as
% \begin{ltxoutput}
% \begin{alltt}\catcode\%=9\normalfont
%There was an old party of Lyme
%Who married three wives at one time.
%      When asked: `Why the third?' 
%      He replied: `One's absurd, 
%And bigamy, sir, is a crime.'
% \end{alltt}
% \end{ltxoutput}
%
% More exotically you could use the TeX |\parshape| command:
% \begin{lstlisting}
% \parshape = 5 0pt \linewidth 0pt \linewidth 
%               2em \linewidth 2em \linewidth 0pt \linewidth
% \noindent There was an old party of Lyme \\
% Who married three wives at one time. \\
% When asked: `Why the third?' \\
% He replied: `One's absurd, \\
% And bigamy, sir, is a crime.' \par
% \end{lstlisting}
% which will be typeset as:
% \begin{ltxoutput*}
% \parshape = 5 0pt \linewidth 0pt \linewidth 
%               2em \linewidth 2em \linewidth 0pt \linewidth
% \noindent There was an old party of Lyme \\
% Who married three wives at one time. \\
% When asked: `Why the third?' \\
% He replied: `One's absurd, \\
% And bigamy, sir, is a crime.' \par
% \end{ltxoutput*}
%    All of this is about as much assistance as standard (La)TeX provides.
%
%
% \clearpage
% \section{The \Lpack{verse} package} \label{sec:usc}
%
% The code provided by the \Lpack{verse} package is meant to help
% with some aspects of typesetting poetry but does not, and cannot,
% provide a comprehensive solution to all the requirements that
% will arise.
%
% A brief introduction is included to get started quickly; see the examples in Section~\ref{sec:ex} for more context.
%
% \subsection{Brief introduction}
%
% The \Lpack{verse} package provides the |verse| environment for typesetting verses, overwriting \LaTeX's original definition.
% Every line in a verse environment must end with |\\|, and every stanza within a verse should end with |\\!| (an empty line afterwards is optional for readability).
% These requirements allow line numbering to work correctly in all cases.
% Use the \cs{poemlines}\marg{N} command to number every \meta{N}th line of a poem.
%
% Use the \cs{poemtitle}\marg{title} command (just before the |verse| environment) to give each poem a title; commands are provided to adjust the formatting and include the poem into the standard table of contents.
%
% Each stanza within a verse may optionally be surrounded by either an |altverse| or |patverse| environment to effect specific typesetting; |altverse| indents every second line of a stanza, and |patverse| allows arbitrary indentation based on the \meta{pattern} given by \cs{indentpattern}\marg{pattern}.
% The command \cs{flagverse}, placed at the very beginning of a stanza places a `title'; e.g., for numbering and otherwise labelling stanzas.
%
%
% \subsection{Comprehensive documentation}
%
% \subsubsection{Main verse environments}
%
% \DescribeEnv{verse}
% The |verse| environment provided by the package is an extension
% of the usual LaTeX environment. The environment takes one optional
% parameter, which is a length; for example |\begin{verse}[4em]|.
% You may have noticed that the earlier verse examples are all
% near the left margin, whereas verses usually look better if they
% are typeset about the center of the page. The length parameter,
% if given, should be about the length of an average line, and then
% the entire contents will be typeset with the mid point of the length
% centered horizontally on the page.
%
% \DescribeMacro{\versewidth}
% The length |\versewidth| is provided as a convenience. It may be used,
% for example, to calculate the length of a line of text for use
% as the optional argument to the |verse| environment: 
% \begin{lstlisting}
% \settowidth{\versewidth}{This is the average line,}
% \begin{verse}[\versewidth]
% \end{lstlisting}
%
% \DescribeEnv{altverse}
% Within the |verse| environment verses are separated by a blank line
% in the input. Individual verses within |verse| may, however, 
% be enclosed in the |altverse| environment. This has the effect of
% indenting the 2nd, 4th, etc., lines of the verse by the length |\vgap|.
%
% \DescribeEnv{patverse}
% Individual verses within the |verse| environment may be enclosed
% in the |patverse| environment. Within the environment the indentation
% of each line is specified by an indentation pattern, which consists
% of an array of digits, $d_{1}$ to $d_{n}$, and the $n^{th}$ line is
% indented by $d_{n}$ times |\vgap|. However, the first line is
% not indented, irrespective of the value of $d_{1}$.
%
% \DescribeEnv{patverse*}
% The |patverse*| environment is similar to |patverse| environment,
% except that the pattern will keep on repeating itself.
%
% \DescribeMacro{\indentpattern}
% The indentation pattern for a |patverse| environment is specified
% via the |\indentpattern{|\meta{digits}|}| command. If the pattern is
% shorter than the number of lines in a verse, the trailing lines will
% not be indented.
%
% \subsubsection{Other verse commands}
%
% \DescribeMacro{\\}
% Within the |verse| environment, the macro |\\| must be used at the
% end of each line of a verse, except for the last line in each stanza.
% If the lines in a poem are to be numbered then
% \DescribeMacro{\\!}
% |\\!| must be used at the 
% end of the last line in each stanza (the |\\| macro increments the line
% numbers).
%
% \DescribeMacro{\\*}
% The starred version, |\\*|, prohibits a page break after the
% line.
% \DescribeMacro{\\>}
% The |\\>| version causes a linebreak within a verse line.
%
% The |\\| macro in its various forms can also take an optional length 
% argument, like |\\[30pt]|
% which will insert |30pt| of vertical space; in the case of |\\>[30pt]|
% an additional 30pt of horizontal space will be inserted after the
% linebreak (effectively |\\>| is shorthand for |\verselinebreak|).
%
% The allowable forms of the
% macro are:
% \begin{center}
% |\\|, |\\*|. |\\!|, |\\>|, |\\[...]|, |\\*[...]|, |\\![...]|,
% and |\\>[...]|.
% \end{center}
%
% \DescribeMacro{\vin}
% \DescribeMacro{\vgap}
% The command |\vin| is shorthand for |\hspace{\vgap}| for use
% at the start of an indented line of verse. The length |\vgap|
% (initially 1.5em) can be changed by |\setlength| or |\addtolength|.
%
% \DescribeMacro{\vindent}
% When a verse line is too long to fit within the typeblock it is
% wrapped onto the next line with a space, given by the value of the
% length \cs{vindent}.
%
% \DescribeMacro{\verselinebreak}
% Using the command |\verselinebreak[|\meta{length}|]| will cause 
% later text in the
% line of the verse to be typeset indented on the following line.
% If the optional length argument is not given the indentation is 
% |\vgap|, otherwise the indentation is given by \meta{length} plus |\vgap|.
% The broken
% line will count as a single line as far as the |altverse| and |patverse|
% environments are concerned (see also the |\\>| macro).
%
% \DescribeMacro{\flagverse}
% \DescribeMacro{\vleftskip}
% Putting the command |\flagverse{|\meta{flag}|}| at the start of a line
% of verse will typeset \meta{flag} towards the left margin, ending
% a distance |\vleftskip| before the verse line.
%
% \subsubsection{Generic verse formatting}
%
% \DescribeMacro{\stanzaskip}
% The length |\stanzaskip| controls the spacing between stanzas.
% It may be changed like any other length.
%
% \DescribeMacro{\leftmargini}
% All verse lines have a minimum indent given by the length \cs{leftmargini}
% which also applies to any list environment. To change the minimum
% indent for verses do something along the lines:
% \begin{lstlisting}
% \newlength{\saveleftmargini}
% \setlength{\saveleftmargini}{\leftmargini}
% \setlength{\leftmargini}{-1em}% for example to outdent verse
% %  verses
% \setlength{\leftmargini}{\saveleftmargini}% restore original value
% \end{lstlisting}
%
%
% \subsubsection{Line numbering}
%
% \DescribeMacro{\poemlines}
% The declaration |\poemlines{|\meta{nth}|}| will cause every \meta{nth}
% lines of succeeding verses to be numbered. For example, |\poemlines{5}|
% will number every fifth line. The default is |\poemlines{0}| which prevents
% any numbering.
%
% \DescribeMacro{\setverselinenums}
% The command \cs{setverselinenums}\marg{firstlinenum}\marg{startnumsat}
% can be used to set the number of the first verse line to \meta{firstlinenum}
% instead of the default `1' and to specify that the first printed line number
% should be for line number \meta{startnumsat}. If used the command must be
% given within the \texttt{verse} environment before the first line of the
% verses. For example, if you were quoting portions of poems from a source
% where the lines were numbered, your first line might be the 112th of the 
% original and that line was originally numbered: \\
% \verb?\setverselinenums{112}{112}? \\
% or if it was line 115 that was first numbered: \\
% \verb?\setverselinenums{112}{115}? 
%
% Note that the numbers must be such that the following relationship holds: \\
% \verb?firstlinenum <= startnumsat < firstlinenum + poemlines?
%
%
% \DescribeMacro{\thepoemline}
% \DescribeMacro{\verselinenumfont}
% Lines are numbered via \cs{thepoemline} which defaults to typesetting 
% arabic numerals via: \\
% \verb?\renewcommand*{\thepoemline}{\arabic{poemline}}? \\
% The particular font is defined by \cs{verselinenumfont}\marg{font-spec},
% with default: \\
% \verb?\verselinenumfont{\rmfamily}? \\
%
% \DescribeMacro{\vrightskip}
% \DescribeMacro{\verselinenumbersleft}
% \DescribeMacro{\verselinenumbersright}
% By default the numbers are typeset at the distance \cs{vrightskip} into the 
% right margin.
% If you want line numbers set at the left use the \cs{verselinenumbersleft}
% declaration. To revert to the default use \cs{verselinenumbersright}.
%
%
% \DescribeMacro{\label}
% \DescribeMacro{\ref}
% The standard |\label{|meta{key}|}| command
% can be used inside the |verse| environment, between the end of the text 
% of a line and the line-ending |\\|, to grab that line number, no matter 
% what the setting of |\poemlines|. Elsewhere the standard
% |\ref{|\meta{key}|}| command can be used to refer to the line number.
%
% \subsubsection{Titles}
%
% \DescribeMacro{\poemtitle}
% |\poemtitle[|\meta{short}|}{|\meta{long}|}| typesets the title
% of a poem and makes an entry into the ToC. There is a starred version
% that makes no ToC entry.
%
% \DescribeMacro{\poemtoc}
% The kind of entry made in the ToC by the |\poemtitle| command is
% defined by |\poemtoc|. The initial definition is: \\
% |\newcommand{\poemtoc}{section}| \\
% for a section-like ToC entry. This can be changed to, say, |chapter|
% or |subsection| or \ldots.
%
% \DescribeMacro{\poemtitlefont}
% This macro specifies the font and positioning of the poem title. Its
% initial definition is: \\
% |\newcommand{\poemtitlefont}{\normalfont\bfseries\large\centering}| \\
% to give a |\large| bold centered title. This can of course be renewed
% if you want something else.
%
% \DescribeMacro{\beforepoemtitleskip}
% \DescribeMacro{\afterpoemtitleskip}
% These two lengths are the vertical space before and after the |\poemtitle|
% title text. They are initially defined to give the same spacing
% as for a |\section| title. They can be changed by |\setlength| or
% |\addtolength| for different spacings.
%
%
% \DescribeMacro{\poemtitlemark}
% The |\poemtitle| macro, but not |\poemtitle*|,
% calls the |\poemtitlemark{|\meta{title}|}| macro,
% which is defined to do nothing. This would probably be changed by a
% pagestyle definition (like |\sectionmark| or |\chaptermark|).
%
% \subsection{Supports}
%
%    The package includes some macros for supporting the |patverse|
% environment which may be more generally useful. See the code section
% for examples on how these may be used.
%
% \DescribeMacro{\newarray}
% |\newarray{|\meta{arrayname}|}{|\meta{low}|}{|\meta{high}|}| defines
% the \meta{arrayname} array, where \meta{arrayname} is a name like
% |MyArray|. The lowest and highest array indices are set to
% \meta{low} and \meta{high} respectively, where both are integer numbers.
%
% \DescribeMacro{\setarrayelement}
% |\setarrayelement{|\meta{arrayname}|}{|\meta{index}|}{|\meta{text}|}|
% sets the \meta{index} location in the \meta{arrayname} array to be 
% \meta{text}. For example: \\
%  |\setarrayelement{MyArray}{23}{$2^{23}$}|.
%
% \DescribeMacro{\getarrayelement}
% |\getarrayelement{|\meta{arrayname}|}{|\meta{index}|}{|\meta{result}|}|
% sets the parameterless macro \meta{result} to the contents of
% the \meta{index} location in the \meta{arrayname} array. For
% example: \\
%  |\getarrayelement{MyArray}{23}{\result}|.
%
% \DescribeMacro{\checkarrayindex}
% |\checkarrayindex{|\meta{arrayname}|}{|\meta{index}|}| checks if
% \meta{arrayname} is an array and if \meta{index} is a valid index for
% the array.
%
% \DescribeMacro{\stringtoarray}
% |\stringtoarray{|\meta{arrayname}|}{|\meta{string}|}| puts each character
% from \meta{string} sequentially into the \meta{arrayname} array, starting
% at index 1. For example: \\
%  |\stringtoarray{MyArray}{Chars}|.
%
% \DescribeMacro{\arraytostring}
% The macro |\arraytostring{|\meta{arrayname}|}{|\meta{result}|}| assumes
% that \meta{arrayname} is an array of characters, and defines the macro
% \meta{result} to be that sequence of characters. For example: \\
% |\arraytostring{MyArray}{\MyString}|.
%
% \DescribeMacro{\checkifinteger}
% |\checkifinteger{|\meta{num}|}| checks if \meta{num} is an integer (not less
% than zero). If it is then |\ifinteger| is set TRUE, otherwise it is set 
% FALSE.
%
% \subsection{Examples}
% \label{sec:ex}
%
%    Here are some sample verses using the package facilities.
% First our old Limerick friend, but titled and centered:
% \begin{lstlisting}
% \renewcommand{\poemtoc}{subsection}
% \poemtitle{A Limerick}
% \settowidth{\versewidth}{There was an old party of Lyme}
% \begin{verse}[\versewidth]
% There was an old party of Lyme \\
% Who married three wives at one time. \\
% \vin When asked: `Why the third?' \\
% \vin He replied: `One's absurd, \\
% And bigamy, sir, is a crime.' \\
% \end{verse}
% \end{lstlisting}
% which gets typeset as below. The default |\poemtoc| is redefined
% to |subsection| so the
% title is entered into the ToC as an unnumbered |\subsection|.
% \begin{ltxoutput}
% \renewcommand{\poemtoc}{subsection}
% \poemtitle{A Limerick}
% \settowidth{\versewidth}{There was an old party of Lyme}
% \begin{verse}[\versewidth]
% There was an old party of Lyme \\
% Who married three wives at one time. \\
% \vin When asked: `Why the third?' \\
% \vin He replied: `One's absurd, \\
% And bigamy, sir, is a crime.' \\
% \end{verse}
% \end{ltxoutput}
%
% \ablankline
%
%     Next is the Garden verse within the |altverse| environment. It
% is titled and centered.
% \begin{lstlisting}
% \settowidth{\versewidth}{But now my love is dead}
% \poemtitle{Love's lost}
% \begin{verse}[\versewidth]
% \begin{altverse}
% \garden
% \end{altverse}
% \end{verse}
% \end{lstlisting}
% which produces:
% \begin{ltxoutput}
% \settowidth{\versewidth}{But now my love is dead}
% \poemtitle{Love's lost}
% \begin{verse}[\versewidth]
% \begin{altverse}
% \garden
% \end{altverse}
% \end{verse}
% \end{ltxoutput}
%
%  \ablankline
%
% It is left up to you how you might want to add information about
% the author of a poem. Here is one example of a macro for this:
% \begin{lstlisting}
% \newcommand{\attrib}[1]{%
%    \nopagebreak{\raggedleft\footnotesize #1\par}}
% \end{lstlisting}
% \newcommand{\attrib}[1]{%
%    \nopagebreak{\raggedleft\footnotesize #1\par}}
%
%    This can be used as in the next bit of doggerel.
% \begin{lstlisting}
% \poemtitle{Fleas}
% \settowidth{\versewidth}{What a funny thing is a flea}
% \begin{verse}[\versewidth]
% What a funny thing is a flea. \\
% You can't tell a he from a she. \\
% But he can. And she can. \\
% Whoopee! \\
% \end{verse}
% \attrib{Anonymous}
% \end{lstlisting}
%
% \begin{ltxoutput}
% \poemtitle{Fleas}
% \settowidth{\versewidth}{What a funny thing is a flea}
% \begin{verse}[\versewidth]
% What a funny thing is a flea. \\
% You can't tell a he from a she. \\
% But he can. And she can. \\
% Whoopee! \\
% \end{verse}
% \attrib{Anonymous}
% \end{ltxoutput}
%
% \ablankline
%
% Here is an example of line wrapping.
% \begin{lstlisting}
% \poemtitle{In the beginning}
% \settowidth{\versewidth}{And objects at rest tended to remain at rest}
% \begin{verse}[\versewidth]
% Then God created Newton, \\
% And objects at rest tended to remain at rest, \\
% And objects in motion tended to remain in motion, \\
% And energy was conserved
%    and momentum was conserved
%    and matter was conserved \\
% And God saw that it was conservative. \\
% \end{verse}
% \attrib{Possibly from \textit{Analog}, circa 1950}
% \end{lstlisting}
%
% \begin{ltxoutput}
% \poemtitle{In the beginning}
% \settowidth{\versewidth}{And objects at rest tended to remain at rest}
% \begin{verse}[\versewidth]
% Then God created Newton, \\
% And objects at rest tended to remain at rest, \\
% And objects in motion tended to remain in motion, \\
% And energy was conserved
%    and momentum was conserved
%    and matter was conserved \\
% And God saw that it was conservative. \\
% \end{verse}
% \attrib{Possibly from \textit{Analog}, circa 1950}
% \end{ltxoutput}
%
% \ablankline
%
% Here is one with a forced line break and a slightly different title style.
% \begin{lstlisting}
% \renewcommand{\poemtitlefont}{\normalfont\large\itshape\centering}
% \poemtitle{Mathematics}
% \settowidth{\versewidth}{Than Tycho Brahe, or Erra Pater:}
% \begin{verse}[\versewidth]
% In mathematics he was greater \\
% Than Tycho Brahe, or Erra Pater: \\
% For he, by geometric scale, \\
% Could take the size of pots of ale;\\ \settowidth{\versewidth}{Resolve by}
% Resolve, by sines \\>[\versewidth] and tangents straight, \\
% If bread or butter wanted weight; \\
% And wisely tell what hour o' the day \\
% The clock does strike, by Algebra. \\
% \end{verse}
% \attrib{Samuel Butler (1612--1680)}
% \end{lstlisting}
%
% \begin{ltxoutput}
% \renewcommand{\poemtitlefont}{\normalfont\large\itshape\centering}
% \poemtitle{Mathematics}
% \settowidth{\versewidth}{Than Tycho Brahe, or Erra Pater:}
% \begin{verse}[\versewidth]
% In mathematics he was greater \\
% Than Tycho Brahe, or Erra Pater: \\
% For he, by geometric scale, \\
% Could take the size of pots of ale;\\ \settowidth{\versewidth}{Resolve by}
% Resolve, by sines \\>[\versewidth] and tangents straight, \\
% If bread or butter wanted weight; \\
% And wisely tell what hour o' the day \\
% The clock does strike, by Algebra. \\
% \end{verse}
% \attrib{Samuel Butler (1612--1680)}
% \end{ltxoutput}
%
% \ablankline
%
% Another limerick, but this time taking advantage of the |patverse|
% environment and numbering every third line.
% \begin{lstlisting}
% \settowidth{\versewidth}{There was a young lady of Ryde}
% \poemtitle{The Young Lady of Ryde}
% \begin{verse}[\versewidth]
% \poemlines{3}
% \indentpattern{00110}
% \begin{patverse}
% There was a young lady of Ryde \\
% Who ate some apples and died. \\
% The apples fermented \\
% Inside the lamented \\
% And made cider inside her inside. \\
% \end{patverse}
% \poemlines{0}
% \end{verse}
% \end{lstlisting}
%
% \begin{ltxoutput}
% \settowidth{\versewidth}{There was a young lady of Ryde}
% \poemtitle{The Young Lady of Ryde}
% \begin{verse}[\versewidth]
% \poemlines{3}
% \indentpattern{00110}
% \begin{patverse}
% There was a young lady of Ryde \\
% Who ate some apples and died. \\
% The apples fermented \\
% Inside the lamented \\
% And made cider inside her inside. \\
% \end{patverse}
% \poemlines{0}
% \end{verse}
% \end{ltxoutput}
%
% \ablankline
%
% The next example is a song you may have heard of. The `forty-niner' in
% line \ref{vs:49} refers to the gold rush  of 1849.
%
% \begin{lstlisting}
% \settowidth{\versewidth}{In a cavern, in a canyon,}
% \poemtitle{Clementine}
% \begin{verse}[\versewidth]
% \poemlines{2}
% \begin{altverse}
% \flagverse{1.} In a cavern, in a canyon, \\
% Excavating for a mine, \\
% Lived a miner, forty-niner, \label{vs:49} \\
% And his daughter, Clementine. \\!
% \end{altverse}
%
% \begin{altverse}
% \flagverse{\textsc{chorus}} Oh my darling, Oh my darling, \\
% Oh my darling Clementine. \\
% Thou art lost and gone forever, \\
% Oh my darling Clementine \\!
% \end{altverse}
% \poemlines{0}
% \end{verse}
% \end{lstlisting}
%
%
% \begin{ltxoutput}
% \settowidth{\versewidth}{In a cavern, in a canyon,}
% \poemtitle{Clementine}
% \begin{verse}[\versewidth]
% \poemlines{2}
% \begin{altverse}
% \flagverse{1.} In a cavern, in a canyon, \\
% Excavating for a mine, \\
% Lived a miner, forty-niner, \label{vs:49} \\
% And his daughter, Clementine. \\!
% \end{altverse}
%
% \begin{altverse}
% \flagverse{\textsc{chorus}} Oh my darling, Oh my darling, \\
% Oh my darling Clementine. \\
% Thou art lost and gone forever, \\
% Oh my darling Clementine \\!
% \end{altverse}
% \poemlines{0}
% \end{verse}
% \end{ltxoutput}
%
%
%  The last example is a much more ambitious use of |\indentpattern|. In
% this case it is defined as: \\
% |\indentpattern{0135554322112346898779775545653222345544456688778899}| \\
% and the result is shown on the next page.
%
%
% \clearpage
% \begin{ltxoutput}
% \poemtitle{Mouse's Tale}
% \settowidth{\versewidth}{a mouse that morning}
% \indentpattern{0135554322112346898779775545653222345544456688778899}
% \begin{verse}[\versewidth]
% \setlength{\vgap}{1em}
% \begin{patverse}
% \large Fury said to \\
%   a mouse, That \\
%   he met \\
%   in the \\
%   house, \\
% \normalsize `Let us \\
%   both go \\
%   to law: \\
%   \emph{I} will \\
%   prosecute \\
%   \textit{you.} --- \\
%   Come, I'll \\
% \small take no \\
%   denial; \\
%   We must \\
%   have a \\
%   trial: \\
%   For \\
% \footnotesize really \\
%   this \\
%   morning \\
%   I've \\
%   nothing \\
%   to do.' \\
%   Said the \\
%   mouse to \\
% \scriptsize the cur, \\
%   Such a \\
%   trial, \\
%   dear sir, \\
%   With no \\
%   jury or \\
%   judge, \\
%   would be \\
%   wasting \\
%   our breath.' \\
% \tiny  `I'll be \\
%   judge, \\
%   I'll be \\
%   jury.' \\
%   Said \\
%   cunning \\
%   old Fury; \\
%   `I'll try \\
%   the whole \\
%   cause \\
%   and \\
%   condemn \\
%   you \\
%   to \\
%   death.'  \par
% \end{patverse}
% \end{verse}
% \attrib{Lewis Carrol, \textit{Alice's Adventures in Wonderland}, 1865}
% \end{ltxoutput}
%
%
% \StopEventually{
% \bibliographystyle{alpha}
% \begin{thebibliography}{GMS94}
% \bibitem[GMS94]{GOOSSENS94}
% Michel Goossens, Frank Mittelbach, and Alexander Samarin.
% \newblock \emph{The LaTeX Companion}.
% \newblock Addison-Wesley Publishing Company, 1994.
% \bibitem[Wil01]{RUMOUR}
% Peter Wilson.
% \newblock \emph{A Rumour of Humour: A scientist's commonplace book}.
% \newblock To be published.
% \end{thebibliography}
% }
%
%
% \clearpage
% \section{The package code} \label{sec:code}
%
%    To try and avoid name clashes, all the internal commands include
% the string |@vs|.
%
% \subsection{Preliminaries}
%
%    Announce the name and version of the package, which requires
% \LaTeXe.
%    \begin{macrocode}
%<*usc>
\NeedsTeXFormat{LaTeX2e}
\ProvidesPackage{verse}[2009/09/04 v2.4a verse typesetting]
%    \end{macrocode}
%
% For reference, here is the original definition of the |verse| environment
% from \file{classes.dtx}, based on |\let|ting |\\| equal |\@centercr|.
% \begin{lstlisting}
% \newenvironment{verse}
%    {\let\\\@centercr
%     \list{}{\itemsep      \z@
%             \itemindent   -1.5em%
%             \listparindent\itemindent
%             \rightmargin  \leftmargin
%             \advance\leftmargin 1.5em}%
%    \item\relax}
%    {\endlist}
% \end{lstlisting}
%
% \subsection{Verse code}
%
%
% \begin{macro}{vslineno}
% \begin{macro}{poemline}
% \begin{macro}{\c@fvsline}
% \begin{macro}{modulo@vs}
% \begin{macro}{verse@envctr}
% \begin{macro}{\theHpoemlines}
% We need a counter for verse lines and poem lines, and one for unique
% hyperref anchors (based on the verse environment). Also one for specifying
% the start of line numbering.
% \changes{v2.0}{2002/03/24}{Added poemline and modulo@vs counters}
% \changes{v2.22}{2005/08/22}{Added verse@envctr counter and 
%                \cs{theHpoemlines} for hyperref}
% \changes{v2.4}{2007/01/10}{Added fvsline counter}
%    \begin{macrocode}
\newcounter{vslineno}
\newcounter{poemline}
\newcounter{fvsline}
  \setcounter{fvsline}{0}
\newcounter{modulo@vs}
\newcounter{verse@envctr}\setcounter{verse@envctr}{0}
\newcommand*{\theHpoemline}{\arabic{verse@envctr}.\arabic{poemline}}
%    \end{macrocode}
% \end{macro}
% \end{macro}
% \end{macro}
% \end{macro}
% \end{macro}
% \end{macro}
%
% \begin{macro}{\poemlines}
% |\poemlines{|\meta{nth}|}| specifies that every \meta{nth} poem line 
% should be numbered. Default is not to number any lines.
% \changes{v2.0}{2002/03/24}{Added \cs{poemlines}}
%    \begin{macrocode}
\newcommand{\poemlines}[1]{%
  \ifnum#1>\z@
    \setcounter{modulo@vs}{#1}%
  \else
    \setcounter{modulo@vs}{0}%
  \fi
}
\poemlines{0}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\verselinenumfont}
% \begin{macro}{\vlvnumfont}
% Set the font for line numbers.
% \changes{v2.3}{2006/01/14}{Added \cs{verselinenumfont} and \cs{vlvnumfont}}
%    \begin{macrocode}
\newcommand*{\verselinenumfont}[1]{\def\vlnumfont{#1}}
\verselinenumfont{\rmfamily}
%    \end{macrocode}
% \end{macro}
% \end{macro}
%
% \begin{macro}{\setverselinenums}
% \cs{setverslinenums}\marg{firstlinenum}\marg{startnumsat} sets the
% number of the first verse line to be \meta{firstlinenum} and the
% first line to be numbered to be \meta{startnumsat}. Note that
% \verb?startnumsat < (firstlinenum + poemlines)?
% \changes{v2.4}{2007/01/10}{Added \cs{setverselinenums}}
%    \begin{macrocode}
\newcommand*{\setverselinenums}[2]{%
%    \end{macrocode}
% Set the poemline counter to \verb?#1?.
%    \begin{macrocode}
  \setcounter{poemline}{#1}\addtocounter{poemline}{\m@ne}%
  \refstepcounter{poemline}%
  \ifnum\c@modulo@vs>\z@
%    \end{macrocode}
% If line numbers are to be printed, set \cs{c@fvsline} to a suitable
% value so that the first number to be printed will be line \verb?#2?.
%    \begin{macrocode}
    \@tempcnta #2\relax
    \divide\@tempcnta\c@modulo@vs
    \multiply\@tempcnta\c@modulo@vs
    \c@fvsline #2\relax
    \advance\c@fvsline-\@tempcnta
  \fi
}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\getmodulo@vs}
% This returns either nothing or a poem line number for printing.
% \changes{v2.0}{2002/03/24}{Added \cs{getmodulo@vs}}
% \changes{v2.4}{2007/01/10}{Modified \cs{getmodulo@vs} for specified start
%                            of line numbers}
%    \begin{macrocode}
\newcommand{\getmodulo@vs}{\bgroup
  \ifnum\c@modulo@vs<\@ne   % no line numbers
  \else
    \ifnum\c@modulo@vs<\tw@ % every line numbered
      \vlnumfont\thepoemline
    \else
      \@tempcnta\c@poemline
      \advance\@tempcnta -\c@fvsline
      \divide\@tempcnta\c@modulo@vs
      \multiply\@tempcnta\c@modulo@vs
      \advance\@tempcnta\c@fvsline
      \ifnum\@tempcnta=\c@poemline\vlnumfont\thepoemline\fi
    \fi
  \fi
\egroup}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\ifaltindent}
% This should be set TRUE for indenting alternate lines.
%    \begin{macrocode}
\newif\ifaltindent
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\ifpattern}
% This should be set TRUE for indenting lines according to a pattern.
%    \begin{macrocode}
\newif\ifpattern
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\ifstarpattern}
% This should be set TRUE for indenting lines according in a |patverse*|
% environment.
% \changes{v2.1}{2002/03/8}{Added \cs{ifstarpattern}}
%    \begin{macrocode}
\newif\ifstarpattern
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\versewidth}
% |\versewidth| is a convenience length for the user.
%    \begin{macrocode}
\newlength{\versewidth}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\vgap}
% \begin{macro}{\vin}
% \begin{macro}{\vindent}
% \begin{macro}{\stanzaskip}
% The length |\vgap| is used as the basis for spacing. |\vin| makes
% a horizontal space of |\vgap| and |\vindent| is the indentation
% of wrapped lines in a verse. |\stanzaskip| controls the space
% between stanzas.
% \changes{v2.2}{2002/07/18}{Added \cs{stanzaskip}}
%    \begin{macrocode}
\newlength{\vgap}
\setlength{\vgap}{1.5em}
\newcommand{\vin}{\hspace*{\vgap}}
\newlength{\vindent}
\setlength{\vindent}{2\vgap}
\newlength{\stanzaskip}
\setlength{\stanzaskip}{0.75\baselineskip}
%    \end{macrocode}
% \end{macro}
% \end{macro}
% \end{macro}
% \end{macro}
%
% \begin{macro}{\vleftskip}
% \begin{macro}{\vrightskip}
% Skips to the left and right of a line of verse.
% \changes{v2.0}{2002/03/24}{Added \cs{vleftksip} and \cs{vrightskip}}
%    \begin{macrocode}
\newlength{\vleftskip}
\setlength{\vleftskip}{30pt}
\newlength{\vrightskip}
\setlength{\vrightskip}{10pt}
%    \end{macrocode}
% \end{macro}
% \end{macro}
%
% \begin{macro}{\flagverse}
% |\flagverse{|\meta{flag}|}| inserts \meta{flag} at the left (of a line).
% \changes{v2.0}{2002/03/24}{Added \cs{flagverse}}
%    \begin{macrocode}
\newcommand{\flagverse}[1]{%
  \hskip-\vleftskip\llap{#1}\hskip\vleftskip
  \ignorespaces
}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\verselinebreak}
% Break a verse line by inserting \cs{newline}.\footnote{In an email to me
% dated 2006/01/13 Aaron Rendahl pointed out that this should include
% an \cs{ignorespaces}.}
% \changes{v2.0}{2002/03/24}{Modified \cs{verselinebreak}}
% \changes{v2.1}{2002/03/28}{Modified \cs{verselinebreak}}
% \changes{v2.3}{2006/01/14}{Added \cs{ignorespaces} to \cs{verselinebreak}}
%    \begin{macrocode}
\newcommand*{\verselinebreak}[1][\z@]{%
  \newline\hspace*{#1}%
  \ignorespaces
}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\incr@vsline}
% Increment the line counters.
% \changes{v2.0}{2002/03/24}{Added poemline counter to \cs{incr@vsline}}
%    \begin{macrocode}
\newcommand{\incr@vsline}{%
  \refstepcounter{poemline}%
  \stepcounter{vslineno}%
}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\@vsifbang}
% Like the kernel |\@ifstar| except it looks for an exclamation mark!
% \changes{v2.0}{2002/03/24}{Added \cs{@vsifbang}}
%    \begin{macrocode}
\newcommand{\@vsifbang}[1]{\@ifnextchar !{\@firstoftwo{#1}}}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\@vsifgt}
% Like the kernel |\@ifstar| except it looks for a |>| character.
% \changes{v2.1}{2002/03/28}{Added \cs{@vsifgt}}
%    \begin{macrocode}
\newcommand{\@vsifgt}[1]{\@ifnextchar >{\@firstoftwo{#1}}}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\@vstypelinenumright}
% \begin{macro}{\@vstypelinenumleft}
% \begin{macro}{\verselinenumbersright}
% \begin{macro}{\verselinenumbersleft}
% These control the typesetting of verse line numbers to the
% right and to the left of the verse. Default is to set them at
% the right.
% \changes{v2.3}{2006/01/14}{Added left/right switching line numbers}
%    \begin{macrocode}
\newcommand*{\@vstypelinenumright}{%
  \hfill\rlap{\kern\vrightskip\kern\rightmargin\getmodulo@vs}%
}
\newcommand*{\@vstypelinenumleft}{%
  \hfill\rlap{\kern-\textwidth\kern-\vrightskip\getmodulo@vs}%
}
\newcommand*{\verselinenumbersright}{\def\@vstypelinenum{\@vstypelinenumright}}
\newcommand*{\verselinenumbersleft} {\def\@vstypelinenum{\@vstypelinenumleft}}
\verselinenumbersright
%    \end{macrocode}
% \end{macro}
% \end{macro}
% \end{macro}
% \end{macro}
%
% \begin{macro}{\@vscentercr}
% This puts the poem line number in the margin, increments
% the line numbers, and then deals with the options. It is based
% on the kernel |\@centercr|.
% This has to handle various forms of the |\\| command: |\\|,
% |\\*|, |\\!|, and |\\>|, together with an optional length argument.
% \changes{v1.1}{2001/08/03}{Changed definition of \cs{@centercrplus}}
% \changes{v2.0}{2002/03/24}{Renamed \cs{@centercrplus} as \cs{@vscentercr}}
% \changes{v2.0}{2002/03/24}{Major rewrite of \cs{@vscentercr} and friends}
% \changes{v2.1}{2002/03/28}{Added greater than character to \cs{@vscentercr}}%
% \changes{v2.3}{2006/01/14}{Used \cs{@vstypelinenum} in \cs{@vscentercr}}
%    \begin{macrocode}
\newcommand{\@vscentercr}{%
  \ifhmode \unskip\else \@nolnerr\fi
  \@vstypelinenum
%%%%  \hfill\rlap{\kern\vrightskip\kern\rightmargin\getmodulo@vs}%
%    \end{macrocode}
% For |>| call |\verselinebreak| to process it.
%    \begin{macrocode}
  \@vsifgt{\verselinebreak}{%
    \incr@vsline
%    \end{macrocode}
% If the call is |\\*...| call |\@vsxcentercr| to handle the |*...|.
% If the call is |\\!|, do nothing.
% If the call is |\\![...]|, call |\@vsicentercr| to handle the |[...]|.
% Otherwise, call |\@vsxcentercr|.
%    \begin{macrocode}
    \par\@ifstar{\nobreak\@vsxcentercr}{%
      \@vsifbang{\@ifnextchar[ {\@vsicentercr}{}}{\@vsxcentercr}%
    }%
  }%
}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\@vsxcentercr}
% Processes |\\*|, and either calls |\@vsicentercr| to handle a |[length]|,
% or |\start@vsline|.
% \changes{v2.0}{2002/03/24}{Added \cs{@vsxcentercr}}
%    \begin{macrocode}
\newcommand{\@vsxcentercr}{%
  \addvspace{-\parskip}%
  \@ifnextchar[ {\@vsicentercr}{\start@vsline}%
}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\@vsicentercr}
% Processes |(\\...)[length]| and then calls |\start@vsline|.
% \changes{v2.0}{2002/03/24}{Added \cs{@vsicentercr}}
%    \begin{macrocode}
\def\@vsicentercr[#1]{\vskip #1\ignorespaces \start@vsline}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\start@vsline}
% This is called at the start of every verse line except the first.
% \changes{v1.1}{2001/08/03}{Added \cs{start@vsline}}
% \changes{v2.1}{2002/03/28}{Added \cs{ifstarpattern} to \cs{start@vsline}}
% \changes{v2.21}{2004/03/22}{Changed \cs{thevslineno} to \cs{c@vslineno} in
%                             \cs{start@vsline}}
%    \begin{macrocode}
\newcommand{\start@vsline}{%
  \ifaltindent\ifodd\c@vslineno\else\vin\fi\fi%
  \ifpattern\get@vsindent\fi%
  \ifstarpattern\getstar@vsindent\fi
}
%    \end{macrocode}
% \end{macro}
%
% \begin{environment}{verse}
% The extended |verse| environment. It sets the verse line counter,
% then defines the particular list environment adjusting the margins
% to center according to the length parameter. If the length parameter
% is at least the |\linewidth| then the `centering' defaults to
% the original |verse| layout.
% \changes{v1.1}{2001/08/03}{Initialise the line counter to 1, not 0, in
%                all cases}
% \changes{v1.2}{2001/10/28}{Fixed new verse environment to match spacings
%                of the original (misplaced close brace)}
% \changes{v2.2}{2002/07/18}{Added \cs{stanzaskip} to the verse environment}
% \changes{v2.22}{2005/08/22}{Added verse@envctr to the verse environment}
%    \begin{macrocode}
\renewenvironment{verse}[1][\linewidth]{%
  \stepcounter{verse@envctr}%
  \setcounter{poemline}{0}\refstepcounter{poemline}%
  \setcounter{vslineno}{1}%
  \let\\=\@vscentercr
  \list{}{\itemsep \z@
          \itemindent  -\vindent%
          \listparindent\itemindent
          \parsep       \stanzaskip
          \ifdim #1 < \linewidth
            \rightmargin        \z@
            \setlength{\leftmargin}{\linewidth}%
            \addtolength{\leftmargin}{-#1}%
            \addtolength{\leftmargin}{-0.5\leftmargin}%
          \else
            \rightmargin        \leftmargin
          \fi
          \addtolength{\leftmargin}{\vindent}}%
  \item[]%
}
{\endlist}
%    \end{macrocode}
% \end{environment}
%
% \begin{environment}{altverse}
% This sets |\altindenttrue| (afterwards false) and initialises the line counter.
% \changes{v2.1}{2002/03/28}{Added \cs{starpatternfalse} to altverse}
%    \begin{macrocode}
\newenvironment{altverse}%
  {\starpatternfalse\patternfalse\altindenttrue\setcounter{vslineno}{1}}%
  {\altindentfalse}
%    \end{macrocode}
% \end{environment}
%
% \subsection{Pattern code}
%
%    The pattern code is based on the idea of converting a string of
% digits to an array of digits, and then being able to access the
% digit at a particular position in the array.
% \changes{v1.1}{2001/08/03}{Added all the pattern code}
%
% \begin{macro}{\vs@nameedef}
% A shorthand for using |\protected@edef|.
%    \begin{macrocode}
\newcommand{\vs@nameedef}[1]{%
  \expandafter\protected@edef\csname #1\endcsname
}
%    \end{macrocode}
% \end{macro}
%
%
% \begin{macro}{\ifbounderror}
% A flag set TRUE if an attempt is made to access an array element outside
% the array limits.
%    \begin{macrocode}
\newif\ifbounderror
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\ifinteger}
%  A flag to indicate if a `number' is an integer (TRUE) or not (FALSE).
%    \begin{macrocode}
\newif\ifinteger
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\c@chrsinstr}
% A counter for the number of characters.
%    \begin{macrocode}
\newcounter{chrsinstr}  % CHARactersINSTRing
%    \end{macrocode}
% \end{macro}
%
%
% \begin{macro}{\newarray}
% |\newarray{|\meta{arrayname}|}{|\meta{low}|}{|\meta{high}|}| defines
% an array called \meta{arrayname} (no backslash e.g. |MyArray|), 
% with low and high limits \meta{low} and \meta{high}.
%    \begin{macrocode}
\newcommand{\newarray}[3]{%
  \vs@nameedef{#1-low}{#2}%
  \vs@nameedef{#1-high}{#3}%
  \ifnum #3<#2
    \PackageError{verse}{Limits for array #1 are in reverse order}{\@ehc}%
  \fi
}
%    \end{macrocode}
% \end{macro}
%
%
% \begin{macro}{\stringtoarray}
% |\stringtoarray{|\meta{arrayname}|}{|\meta{string}|}| puts each character
% from \meta{string} sequentially into the \meta{arrayname} array, starting
% with \meta{low} = 1. It checks for an empty \meta{string} and handles that
% specially.
%    \begin{macrocode}
\newcommand{\stringtoarray}[2]{%
  \def\@vsarrayname{#1}%
  \protected@edef\the@vsstring{#2}%
  \newarray{\@vsarrayname}{1}{1}%
  \@ifmtarg{#2}{%
    \c@chrsinstr \z@
    \@namedef{\@vsarrayname-1}{}%
  }{%
    \c@chrsinstr \@ne
    \expandafter\@vsstringtoarray \the@vsstring\@vsend
  }%
}
%    \end{macrocode}
% \end{macro}
%
%
% \begin{macro}{\@vsstringtoarray}
% Recursively adds characters to the array |\@vsarrayname|, incrementing
% the array's high limit.
%    \begin{macrocode}
\def\@vsstringtoarray #1#2\@vsend{%
  \@namedef{\@vsarrayname-\the\c@chrsinstr}{#1}%
  \vs@nameedef{\@vsarrayname-high}{\the\c@chrsinstr}%
  \@ifmtarg{#2}{%
    \def\@vsinext{}%
  }{%
    \advance\c@chrsinstr \@ne
    \def\@vsinext{%
      \@vsstringtoarray #2\@vsend%
    }%
  }%
  \@vsinext
}
%    \end{macrocode}
% \end{macro}
%
%
% \begin{macro}{\setarrayelement}
% |\setarrayelement{|\meta{arrayname}|}{|\meta{index}|}{|\meta{value}|}| sets
% the \meta{arrayname} array's element at \meta{index} to \meta{value}.
%    \begin{macrocode}
\newcommand{\setarrayelement}[3]{%
  \checkarrayindex{#1}{#2}%
  \vs@nameedef{#1-#2}{#3}%
}
%    \end{macrocode}
% \end{macro}
%
%
% \begin{macro}{\getarrayelement}
% |\getarrayelement{|\meta{arrayname}|}{|\meta{index}|}{|\meta{value}|}|
% defines the parameterless macro \meta{value} (e.g., |\result|) to be
% the value at \meta{index} in the \meta{arrayname} array.
%    \begin{macrocode}
\newcommand{\getarrayelement}[3]{%
  \checkarrayindex{#1}{#2}%
  \protected@edef#3{\@nameuse{#1-#2}}%
}
%    \end{macrocode}
% \end{macro}
%
%
% \begin{macro}{\checkarrayindex}
% |\checkarrayindex{|\meta{arrayname}|}{|\meta{index}|}| checks that
% the \meta{index} of the \meta{arrayname} array is valid. |\ifbounderror|
% is set FALSE if everything is OK, otherwise it is set TRUE.
%    \begin{macrocode}
\newcommand{\checkarrayindex}[2]{%
  \bounderrorfalse
  \expandafter\ifx\csname #1-low\endcsname\relax
    \ifpattern\else
      \PackageError{verse}{No array called #1}{\@ehc}%
    \fi
    \bounderrortrue
  \fi
  \ifnum #2<\@nameuse{#1-low}\relax
    \ifpattern\else
      \PackageError{verse}{Index #2 outside limits for array #1}{\@ehc}%
    \fi
    \bounderrortrue
  \fi
  \ifnum #2>\@nameuse{#1-high}\relax
    \ifpattern\else
      \PackageError{verse}{Index #2 outside limits for array #1}{\@ehc}%
    \fi
    \bounderrortrue
  \fi
}
%    \end{macrocode}
% \end{macro}
%
%
% \begin{macro}{\@ifmtarg}
% Provides an if-then-else command for an empty macro argument
% (empty = zero or more spaces only). Use as: \\
%  |\@ifmtarg{arg1}{Code for arg1 empty}{Code for arg1 not empty}| \\
% This code is copied from my \Lpack{ifmtarg} package.
%    \begin{macrocode}
\begingroup
\catcode`\Q=3
\long\gdef\@ifmtarg#1{\@xifmtarg#1QQ\@secondoftwo\@firstoftwo\@nil}
\long\gdef\@xifmtarg#1#2Q#3#4#5\@nil{#4}
\long\gdef\@ifnotmtarg#1{\@xifmtarg#1QQ\@firstofone\@gobble\@nil}
\endgroup
%    \end{macrocode}
% \end{macro}
%
%
% \begin{macro}{\arraytostring}
% |\arraytostring{|\meta{arrayname}|}{|\meta{string}|}| converts the
% characters in the \meta{arrayname} array into the parameterless macro
% \meta{string} (e.g., |\MyString|).
%    \begin{macrocode}
\newcommand{\arraytostring}[2]{%
  \def#2{}%
  \c@chrsinstr = \@nameuse{#1-low}%
  \@vsarraytostring{#1}{#2}%
}
%    \end{macrocode}
% \end{macro}
%
%
% \begin{macro}{\@vsarraytostring}
% |\@vsarraytostring{|\meta{arrayname}|}{|\meta{string}|}| recursively
% adds the (character) elements from \meta{arrayname} to \meta{string}.
%    \begin{macrocode}
\newcommand{\@vsarraytostring}[2]{%
  \ifnum\c@chrsinstr>\@nameuse{#1-high}\else
    \protected@edef#2{#2\@nameuse{#1-\thechrsinstr}}%
    \advance\c@chrsinstr\@ne%
    \@vsarraytostring{#1}{#2}%
  \fi%
}
%    \end{macrocode}
% \end{macro}
%
%
% \begin{macro}{\checkifinteger}
% |\checkifinteger{|\meta{num}|}| checks if \meta{num} is an integer.
% If it is, then |\ifinteger| is set TRUE, otherwise it is set FALSE.
% (Code based on Donald Arseneau's \Lpack{cite} package).
%    \begin{macrocode}
\newcommand{\checkifinteger}[1]{%
  \protected@edef\@vsa{#1}%
  \ifcat _\ifnum9<1\gobm{#1} _\else A\fi
    \integertrue
  \else
    \integerfalse
  \fi
}
%    \end{macrocode}
% \end{macro}
%
%
% \begin{macro}{\gobm}
% |\gobm{|\meta{num}|}| is defined as \meta{num}. It could be defined as: \\
% |\newcommand{\gobm}[1]{\ifx-#1\expandafter\gobm\else#1\fi}| \\
% which would remove a leading minus sign (hyphen) from its argument
% (|gobm| = gobble minus sign).
% (Code from a posting to CTT by Donald Arseneau on 1997/07/21).
%    \begin{macrocode}
\newcommand{\gobm}[1]{#1}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\indentpattern}
% |\indentpattern{|\meta{digits}|}| stores \meta{digits} for use as
% a verse indentation pattern.
%    \begin{macrocode}
\newcommand{\indentpattern}[1]{%
  \stringtoarray{Array@vs}{#1}%
}
%    \end{macrocode}
% \end{macro}
%
%
% \begin{macro}{\get@vsindent}
% |\get@vsindent| gets the indent pattern digit for the |\thevslineno|,
% then uses this to specify the line indentation as |digit*\vgap|.
% \changes{v2.21}{2004/03/21}{Changed \cs{thevslineno} to
%          \cs{number}\cs{value}\texttt{vslineno} in \cs{get@vsindent}}
%    \begin{macrocode}
\newcommand{\get@vsindent}{%
  \getarrayelement{Array@vs}{\number\value{vslineno}}{\@vspat}%
  \ifbounderror
    \arraytostring{Array@vs}{\@vsp@t}%
    \PackageWarning{verse}{%
      Index `\thevslineno' for pattern `\@vsp@t' is out of bounds}%
    \def\@vspat{0}%
  \else
    \checkifinteger{\@vspat}%
    \ifinteger\else
      \arraytostring{Array@vs}{\@vsp@t}%
      \PackageWarning{verse}{%
       `\@vspat' at index `\thevslineno' in pattern `\@vsp@t' is not a digit}%
      \def\@vspat{0}%
    \fi
  \fi
  \ifcase\@vspat\else\hspace*{\@vspat\vgap}\fi
}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\getstar@vsindent}
% |\getstar@vsindent| gets the indent pattern digit for the |patverse*|
% environment,
% then uses this to specify the line indentation as |digit*\vgap|.
% It lets the pattern repeat by resetting the |vslineno| counter.
% \changes{v2.1}{2002/03/28}{Added \cs{getstar@vsindent}}
%    \begin{macrocode}
\newcommand{\getstar@vsindent}{%
  \expandafter\ifx\csname Array@vs-high\endcsname\relax
    \PackageError{verse}{A pattern has not been specified}{\@ehc}%
  \else
    \ifnum\c@vslineno>\@nameuse{Array@vs-high}%
      \setcounter{vslineno}{1}%
     \fi
     \get@vsindent
  \fi
}
%    \end{macrocode}
% \end{macro}
%
%
% \begin{environment}{patverse}
% The environment for setting verse line indents according to a pattern.
% It starts by setting |\ifpattern| TRUE, any other flags to FALSE,
% and initialises the line number. It ends by setting |\ifpattern| FALSE.
% \changes{v2.1}{2002/03/28}{Added \cs{starpatternfalse} to patverse}
%    \begin{macrocode}
\newenvironment{patverse}
  {\starpatternfalse\patterntrue\altindentfalse\setcounter{vslineno}{1}}
  {\patternfalse}
%    \end{macrocode}
% \end{environment}
%
% \begin{environment}{patverse*}
% The environment for setting verse line indents according to a repeating
% pattern.
% It starts by setting |\ifstarpattern| TRUE, any other flags to FALSE,
% and initialises the line number. It ends by setting |\ifstarpattern| FALSE.
% \changes{v2.1}{2002/03/28}{Added patverse* environment}
%    \begin{macrocode}
\newenvironment{patverse*}
  {\starpatterntrue\patternfalse\altindentfalse\setcounter{vslineno}{1}}
  {\starpatternfalse}
%    \end{macrocode}
% \end{environment}
%
% \subsection{Title code}
%
% \begin{macro}{\poemtitle}
% Typeset a poem title (like |\section| or other). The actual work
% is done by |\@vsptitle| (plain) or |\@vssptitle| (starred).
%    \begin{macrocode}
\newcommand{\poemtitle}{%
  \par
  \secdef\@vsptitle\@vssptitle
}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\poemtoc}
% The kind of entry |\poemtitle| is to make in the ToC.
%    \begin{macrocode}
\newcommand{\poemtoc}{section}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\@vsptitle}
% Typeset a |poemtitle|.
% \changes{v2.22}{2005/08/22}{Added hyperref anchor to \cs{@vsptitle}}
%    \begin{macrocode}
\def\@vsptitle[#1]#2{%
  \@nameuse{phantomsection}%
  \addcontentsline{toc}{\poemtoc}{#1}%
  \poemtitlemark{#1}%
  \@vstypeptitle{#2}%
  \@afterheading
}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\@vssptitle}
% Typeset a |\poemtitle*|.
%    \begin{macrocode}
\def\@vssptitle#1{%
  \@vstypeptitle{#1}
  \@afterheading
}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\@vstypeptitle}
% This \emph{really} typesets the title.
%    \begin{macrocode}
\newcommand{\@vstypeptitle}[1]{%
  \vspace{\beforepoemtitleskip}%
  {\poemtitlefont #1\par}%
  \vspace{\afterpoemtitleskip}%
}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\poemtitlefont}
% \begin{macro}{\poemtitlemark}
% Sets the appearance to the title of a poem, and something for a header.
%    \begin{macrocode}
\newcommand{\poemtitlefont}{\normalfont\large\bfseries\centering}
\newcommand{\poemtitlemark}[1]{}
%    \end{macrocode}
% \end{macro}
% \end{macro}
%
% \begin{macro}{\beforepoemtitleskip}
% \begin{macro}{\afterpoemtitleskip}
% Lengths before and after a poem title, using the |\section| values.
%    \begin{macrocode}
\newlength{\beforepoemtitleskip}
\setlength{\beforepoemtitleskip}{3.5ex \@plus 1ex \@minus .2ex}
\newlength{\afterpoemtitleskip}
\setlength{\afterpoemtitleskip}{2.3ex \@plus.2ex}
%    \end{macrocode}
% \end{macro}
% \end{macro}
%
%    The end of this package.
%    \begin{macrocode}
%</usc>
%    \end{macrocode}
%
% \Finale
% \PrintIndex
%
\endinput
%% \CharacterTable
%%  {Upper-case    \A\B\C\D\E\F\G\H\I\J\K\L\M\N\O\P\Q\R\S\T\U\V\W\X\Y\Z
%%   Lower-case    \a\b\c\d\e\f\g\h\i\j\k\l\m\n\o\p\q\r\s\t\u\v\w\x\y\z
%%   Digits        \0\1\2\3\4\5\6\7\8\9
%%   Exclamation   \!     Double quote  \"     Hash (number) \#
%%   Dollar        \$     Percent       \%     Ampersand     \&
%%   Acute accent  \'     Left paren    \(     Right paren   \)
%%   Asterisk      \*     Plus          \+     Comma         \,
%%   Minus         \-     Point         \.     Solidus       \/
%%   Colon         \:     Semicolon     \;     Less than     \<
%%   Equals        \=     Greater than  \>     Question mark \?
%%   Commercial at \@     Left bracket  \[     Backslash     \\
%%   Right bracket \]     Circumflex    \^     Underscore    \_
%%   Grave accent  \`     Left brace    \{     Vertical bar  \|
%%   Right brace   \}     Tilde         \~}


