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%
% Copyright (C) 2012 by Robin Schneider &lt;ypid23@aol.de&gt;
%
% This work may be distributed and/or modified under the
% conditions of the LaTeX Project Public License, either version 1.3
% of this license or (at your option) any later version.
% The latest version of this license is in
%   http://www.latex-project.org/lppl.txt
% and version 1.3 or later is part of all distributions of LaTeX
% version 2005/12/01 or later.
%
% This work has the LPPL maintenance status `maintained'.
%
% The Current Maintainer of this work is Robin Schneider.
%
% This work consists of the files calcage.dtx and calcage.ins
% and the derived filebase calcage.sty.
%
% \fi
%
% \iffalse
%&lt;*driver&gt;
\ProvidesFile{calcage.dtx}
%&lt;/driver&gt;
%&lt;package&gt;%% See file 'calcage.dtx' for copyright and licence.
%&lt;package&gt;\NeedsTeXFormat{LaTeX2e}[1998/12/01]
%&lt;package&gt;\ProvidesPackage{calcage}
%&lt;*package&gt;
    [2012/09/09 v0.90 Calculate the age in years]
%&lt;/package&gt;
%
%&lt;*driver&gt;
\documentclass[english]{ltxdoc}
\newcommand{\PackageURL}{https://github.com/ypid/latex-packages/tree/master/calcage}
\newcommand{\PackageCTANURL}{http://www.ctan.org/pkg/calcage}
\newcommand{\PackageAuthor}{Robin Schneider}
\newcommand{\PackageAuthorEmail}{ypid23@aol.de}
\newcommand{\PackageName}{\PrintPackage{calcage}}
\newcommand{\PrintPackage}[1]{\textsf{#1}}
\newcommand{\PrintOptionF}[1]{\emph{#1}} %% ^^A This macro is used for
%% ^^A explaining any parameter when they first come up in the documentation.
\newcommand{\DescribePara}[1]{\marginpar{\raggedleft\strut\MacroFont\string #1}}
\usepackage{calcage}
\usepackage{
  babel,
  csquotes,
  xcolor,
  url,
  hypdoc,
  nameref,
}
\GetFileInfo{calcage.dtx}
\hypersetup{
  pdftitle={A manual for \PackageName},
  pdfauthor={\PackageAuthor{} &lt;\PackageAuthorEmail&gt;},
  pdfsubject={\fileinfo},
  baseurl={\PackageURL},
  pdfkeywords={This document corresponds to \PackageName~\fileversion,
    dated \filedate}
}

\title{The \PackageName{} package\thanks{This document
corresponds to \PackageName~\fileversion, dated \filedate.}}
\author{\PackageAuthor \\
  \texttt{\href{mailto:\PackageAuthorEmail?subject=LaTeX package calcage}%
    {\PackageAuthorEmail}%
  }%
}

\EnableCrossrefs
\CodelineIndex
\RecordChanges
\begin{document}
  \DocInput{calcage.dtx}
  \PrintChanges
  \PrintIndex
\end{document}
%&lt;/driver&gt;
% \fi
%
% \CheckSum{122}
%
% \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     \&amp;
%   Acute accent  \'     Left paren    \(     Right paren   \)
%   Asterisk      \*     Plus          \+     Comma         \,
%   Minus         \-     Point         \.     Solidus       \/
%   Colon         \:     Semicolon     \;     Less than     \&lt;
%   Equals        \=     Greater than  \&gt;     Question mark \?
%   Commercial at \@     Left bracket  \[     Backslash     \\
%   Right bracket \]     Circumflex    \^     Underscore    \_
%   Grave accent  \`     Left brace    \{     Vertical bar  \|
%   Right brace   \}     Tilde         \~}
%
% \changes{0.90}{2012/09/09}{Initial version}
%
% \DoNotIndex{\RequirePackage, \DeclareOption, \ProcessOptions}
% \DoNotIndex{\PackageWarning, \MessageBreak}
% \DoNotIndex{\DeclareRobustCommand, \newcommand, \renewcommand, \def, \edef}
% \DoNotIndex{\DeclareStringOption, \ProcessLocalKeyvalOptions}
% \DoNotIndex{\ProcessKeyvalOptions, \SetupKeyvalOptions, \DeclareBoolOption}
% \DoNotIndex{\newenvironment}
% \DoNotIndex{\if, \else, \fi, \ifcase, \or, \ifthenelse, \AND, \OR, \value, \relax}
% \DoNotIndex{\loop, \repeat, \the, \ifnum}
% \DoNotIndex{\equal, \boolean, \@currname, \newcounter, \setcounter}
% \DoNotIndex{\stepcounter, \addtocounter}
% \DoNotIndex{\endinput}
%
% \maketitle
%
% \phantomsection
% \addcontentsline{toc}{section}{\abstractname}
% \begin{abstract}
% The \PackageName{} package can calculate the age in years. \\
% Information site on CTAN: \url{\PackageCTANURL} \\
% Fork me on GitHub: \url{\PackageURL} \end{abstract}
%
% \tableofcontents
%
% \section{Introduction}
% The \PrintPackage{calcage} package can calculate the age of someone or
% something in years. Internally it uses the \PrintPackage{datenumber} package
% to calculate the age in days. The conversion from days to years is
% implemented by this package. It is also taken care about leap years and such
% odd things. So if you enter your birthday you get your exact age in years.
% You can even get the age as number with up to 18 places after the decimal
% separator but I heard that this is a bit uncommon for the age of a person~\dots
%
% \section{Usage}
% Just load the package placing
% \begin{quote}
%   |\usepackage{calcage}|
% \end{quote}
% in the preamble of your \LaTeXe{} source file.
%
% You can also give optional package options to change the default behavior.
% But you can not give values (see \nameref{sec:bugs}). So
% \begin{quote}
%   |\usepackage[presision]{calcage}|
% \end{quote}
% works and sets the presision to 3. But \enquote{presision=3} is going to
% fail~\dots
% \bigskip
%
% \DescribeMacro{\calcage}
% The macro |\calcage| \oarg{optional parameters} \marg{year} \marg{month}
% \marg{day} takes a date and typesets the difference to the current date in
% years.
% \bigskip
%
% There are some optional parameters. \DescribePara{year, month, day} For
% example you can adjust the current date for \PrintPackage{calcage} with the
% keys \enquote{\PrintOptionF{year}}, \enquote{\PrintOptionF{month}} and
% \enquote{\PrintOptionF{day}}. You don't have to specifier all of them. A
% subset is also possible.
%
% Another useful parameter is \enquote{\PrintOptionF{precision}}.
% \DescribePara{precision} With this parameter you can specify how many places
% after the decimal separator you would like to get. The default precision is 0
% which means that |\calcage| will typeset the age in years as integer. If you
% omit a value for \enquote{precision} then the precision will be 3.
%
% The macro |\calcage| can also take a date which is in the future.
% \DescribePara{positive} The default behavior in this case is a negative
% number but you can make the number positive with the
% \enquote{\PrintOptionF{positive}} boolean switch.
%
% The next parameter I would like to show you is the \DescribePara{printyear}
% \enquote{\PrintOptionF{printyear}} boolean switch. With this switch you can
% specify if |\calcage| should add \enquote{year} or rather \enquote{years}
% after the age. This is the default setting.
%
%
% For the previous parameter you may need the possibility
% \DescribePara{yearsuffix} (at least in the German language) to add a single
% character to the plural word. For example
% \begin{quote}
%   |Albert Einstein wurde vor \calcage[yearsuffix]{1879}{03}{14}| \\
%   |geboren.| \\
%   Albert Einstein wurde vor \calcage[printyear=false]{1879}{03}{14} Jahren geboren.
% ^^A Ups you got my. I didn't implement a switch language feautre (yet).
% \end{quote}
% To do this you can use the boolean switch
% \enquote{\PrintOptionF{yearsuffix}}. By default this switch is false.
% If this boolean is true and the German language was selected then a
% \enquote{n} will be added after \enquote{Jahre}. If the English language was
% selected then this switch will not change the output.
%
% And last but not least there is the boolean switch \enquote{numberstring}
% \DescribePara{numberstring} which is true by default. This means that the
% typesetting process of an integer is done by the package
% \PrintPackage{fnumprint} which will typeset the word of a number instead of
% the Arabic number if the value of the number is between 0 and 12. If you
% don't like this behavior you can set the boolean to false with
% \enquote{numberstring=false}.
%
% \section{Bugs}\label{sec:bugs}
% I tried to implement the possibility to change the default behavior as
% package option in a nice way but with the current implementation there is a
% problem with the values. If you give a key with value then the |\setkeys|
% macro which gets these parameters as macro fails. I already tried
% |\expandafter| so if anyone knows where the problem is or has a solution feel
% free to contact me.
% \bigskip
%
% I think there is a little inaccuracy in the conversion from days to years
% because my implementation just removes the leap years before dividing. But in
% my tests this seems to be more theoretically.
%
% The problem only has an effect if leap years are involved because if a leap
% year is calculated then the additional day is subtracted. This means that one
% day is not longer $\frac{1}{366}$ year but $\frac{1}{365}$ year~\dots
%
% \section{Examples}
% \begin{verbatim}
%   \TeX{} Live realeases: \\
%   \calcage{2012}{07}{08} \\
%   \calcage{2011}{07}{20} \\
%   \calcage{2010}{09}{10} \\
%   \calcage{2009}{11}{09}
% \end{verbatim}\vspace{-1.5em}
%   \TeX{} Live realeases: \\
%   \calcage{2012}{07}{08} \\
%   \calcage{2011}{07}{20} \\
%   \calcage{2010}{09}{10} \\
%   \calcage{2009}{11}{09}
%
% \begin{verbatim}
%   Donald Knuth is \calcage{1938}{01}{10} old. \\
%   Donald Knuth will be 100 years old in
%     \calcage[positive, precision]{2038}{01}{10}. \\
%   Albert Einstein died at the age of
%     \calcage[year=1955, month=04, day=18]{1879}{03}{14}. \\
%   Age of Linus Torvalds in years: \calcage[printyear=false]{1969}{12}{28} \\
% \end{verbatim}\vspace{-1.5em}
% Donald Knuth is \calcage{1938}{01}{10} old. \\
% Donald Knuth will be 100 years old in
%   \calcage[positive, precision]{2038}{01}{10}. \\
% Albert Einstein died at the age of
%   \calcage[year=1955, month=04, day=18]{1879}{03}{14}. \\
% Age of Linus Torvalds in years: \calcage[printyear=false]{1969}{12}{28} \\
%
% \StopEventually{}
%
% \newpage
% \section{Implementation}
% \iffalse
%&lt;*package&gt;
% \fi
% This package depends on these packages.
%    \begin{macrocode}
\RequirePackage{fnumprint}[2012/08/27]
\RequirePackage{
  datenumber,
  fp,
  calc,
  xkeyval,
  kvoptions,
  xifthen,
}
%    \end{macrocode}
% \subsection{Declaring the options}
%    \begin{macrocode}
\DeclareStringOption{year}
\DeclareStringOption{month}
\DeclareStringOption{day}
\DeclareStringOption{precision}[3]
\DeclareBoolOption{positive}
\DeclareBoolOption{printyear}
\DeclareBoolOption{yearsuffix}
\DeclareBoolOption{numberstring}
%    \end{macrocode}
% To test if all parameters are valid the macro |\ProcessLocalKeyvalOptions*|
% is expanded to ensure this before leaving the preamble. This is the only
% purpose for the |\ProcessLocalKeyvalOptions*| macro in this case.
%    \begin{macrocode}
\ProcessLocalKeyvalOptions*
%    \end{macrocode}
% The next source code line creates a new macro which captures the parameters
% to use them as default options for the macro |\calcage|.
% If this macro is set to \enquote{precision=4} for example the |\setkeys| is
% going to fail.
%    \begin{macrocode}
\edef\calcage@options{\@ptionlist{\@currname.\@currext}}
%% ^^A \renewcommand{\calcage@options}{precision=4,printyear=false}
%% ^^A Package xkeyval Error: `precision=4' undefined in families `calcage'.
%    \end{macrocode}
% \subsection{Language selection}
% Here comes the language selection part. The counter is already set by the
% \PrintPackage{fnumprint} so I use it's value also in this package because I
% can rely on this counter.\footnote{I am also the maintainer of the
% \PrintPackage{fnumprint} package~\dots}
% If you prefer another language than English or German you can redefine the
% following macro definitions.
%    \begin{macrocode}
\ifcase\value{fnumprint@language}\or
%    \end{macrocode}
% If fnumprint@language is equal 1
%    \begin{macrocode}
  \newcommand{\calcage@yearWord}{Jahr}
  \newcommand{\calcage@yearPluralSuffix}{e}
  \newcommand{\calcage@yearSuffix}{n}
\or
%    \end{macrocode}
% If fnumprint@language is equal 2
%    \begin{macrocode}
  \newcommand{\calcage@yearWord}{year}
  \newcommand{\calcage@yearPluralSuffix}{s}
  \newcommand{\calcage@yearSuffix}{}
\fi
%    \end{macrocode}
% \subsection{Macro definition}
% Some necessary \LaTeX{} counters are declared here before creating the
% |\calcage| macro.
%    \begin{macrocode}
\newcounter{calcage@today}\newcounter{calcage@ageindays}
\newcounter{calcage@myyear}\newcounter{calcage@leapyears}
%    \end{macrocode}
% \begin{macro}{\calcage}
% And now comes the important part -- the definition of |\calcage|.
% The first thing that has to be done is expanding the |\setkeys| macro. It
% sets the default options then the package options get the opportunity to
% overwrite these settings and finally the macro options get the same
% possibility.
%    \begin{macrocode}
\newcommand{\calcage}[4][]{%
  \setkeys{calcage}{precision=0, positive=true, printyear=true,
    yearsuffix=false, numberstring=true,
    year=\the\year, month=\the\month, day=\the\day, \calcage@options, #1}%
  \setmydatenumber{calcage@today}{\calcage@year}{\calcage@month}{\calcage@day}%
  \setmydatenumber{calcage@ageindays}{#2}{#3}{#4}%
%    \end{macrocode}
% Now comes the tricky part which are the leap years~\dots \\
% My first implementation worked with dividing by $365.2425$ but this was not
% perfect. So the current implementation counts how many leap years are between
% the birth year and the current year and subtracts (or adds\footnote{If the
% birth year is in the future because in this case the calcage@ageindays
% counter will be negative.}) this number.
%    \begin{macrocode}
  \setcounter{calcage@myyear}{#2}%
  \setcounter{calcage@leapyears}{0}%
  \ifthenelse{\equal{#2}{\calcage@year}}{}{%
    \ifthenelse{\value{calcage@myyear}&lt;\calcage@year}{%
%    \end{macrocode}
% If the birth year is in the past.
%    \begin{macrocode}
      \loop%
        \stepcounter{calcage@myyear}%
        \ifleapyear{\thecalcage@myyear}\stepcounter{calcage@leapyears}\fi%
        \ifnum\value{calcage@myyear}&lt;\calcage@year%
      \repeat%
    }{%
%    \end{macrocode}
% If the birth year is in the future.
%    \begin{macrocode}
      \loop%
        \ifleapyear{\thecalcage@myyear}\addtocounter{calcage@leapyears}{-1}\fi%
        \addtocounter{calcage@myyear}{-1}%
        \ifnum\value{calcage@myyear}&gt;\calcage@year%
      \repeat%
    }%
  }%
  \setcounter{calcage@ageindays}{\value{calcage@today}
    - \value{calcage@ageindays} - \value{calcage@leapyears}}%
  \ifthenelse{\boolean{calcage@positive} \AND \value{calcage@ageindays} &lt; 0}{%
    \setcounter{calcage@ageindays}{\value{calcage@ageindays} * -1}%
  }{}%
%    \end{macrocode}
% Because we know that every year has now exactly 365 days we can divide by
% that.
%    \begin{macrocode}
  \FPdiv\calcage@age{\thecalcage@ageindays}{365}%
%    \end{macrocode}
% The next step is to truncated the age. There is no rounding used for this. I
% implemented it this way because if the age would be rounded then there would
% be a wrong result in cases like $x.999$ which would become $x+1$ if
% \enquote{precision=0} and that is probably not what you want~\dots
%    \begin{macrocode}
  \FPtrunc\calcage@age{\calcage@age}{\calcage@precision}%
%    \end{macrocode}
% The last thing to do is to typeset the age which is implemented by the next
% few lines of code.
%    \begin{macrocode}
  \ifthenelse{\boolean{calcage@numberstring}
    \AND \equal{\calcage@precision}{0}}%
    {\fnumprint[ein]{\calcage@age}}{\numprint{\calcage@age}}%
  \ifthenelse{\boolean{calcage@printyear}}{%
    ~\calcage@yearWord%
    \ifthenelse{\equal{\calcage@age}{1} \OR \equal{\calcage@age}{-1}}{}{%
      \calcage@yearPluralSuffix%
      \ifthenelse{\boolean{calcage@yearsuffix}}{\calcage@yearSuffix}{}%
    }%
  }{}%
}
%    \end{macrocode}
% \end{macro}
% That's it.
%    \begin{macrocode}
\endinput
%    \end{macrocode}
%
% \iffalse
%&lt;/package&gt;
% \fi
%
% \Finale
\endinput
</pre></body></html>