Help automating calendar creation

Question

I'm doing calendars for all the family, and I have a problem automating the process. I'm using the calendar tikz library.

I need to include the moon phase in the calendar. I can do it with this code

\documentclass{scrartcl}
\usepackage{mathabx}
\usepackage{tikz}
\usetikzlibrary{calendar}
\usepackage{etoolbox}

\newcount\mooncounter
\mooncounter=1

\def\moon{%
\ifnum\mooncounter=1%
    $\newmoon$\global\advance\mooncounter by 1\else
    \ifnum\mooncounter=2% 
        $\rightmoon$\global\advance\mooncounter by 1\else
        \ifnum\mooncounter=3% 
            $\fullmoon$\global\advance\mooncounter by 1\else
            \ifnum\mooncounter=4% 
                $\leftmoon$\global\mooncounter=1
            \fi%
        \fi%
    \fi%
\fi%
}

\begin{document}
\begin{tikzpicture}
    \calendar [
        dates = 2012-12-1 to 2012-12-last,
        week list,
        day xshift = 3em
        ] if (equals = 2012-12-27,
            equals = 2012-12-2,
            equals = 2012-12-7,
            equals = 2012-12-6,
            equals = 2012-12-8,
            equals = 2012-12-9,
            equals = 2012-12-12) [day text = \moon\%d-];
\end{tikzpicture}
\end{document}

First of all, I don't know how \newcount works (just copied the code from other site), but I use it because I can't find the way of doing it with \newcounter or \pgfmathtruncatemacro (I can't make them work in the \calendar). That's why I have this first question: Why the command doesn't work out of the \calendar? I mean. If I write

\begin{document}
    \moon \moon
\end{document}

it doesn't work as I expected. I want it to be cyclic but it shows me two consecutive \newmoons.

Anyway, I want to be able to input the days which have a moon, and then let LaTeX do the rest.

I tried with this:

\newcommand*{\listofmoons}[1]{%
    \edef\listmoons{#1}%
    \def\moons{}%
    \foreach \l in \listmoons {%
        \xappto\moons{if (equals = 2012-12-\l) [day text=\moon\%d-]}
    }%
}

and then use

\begin{tikzpicture}
    \listofmoons{2,6,7,8,9,12,27}
    \calendar [
        dates = 2012-12-1 to 2012-12-last,
        week list,
        day xshift = 3em
        ] \moons;
\end{tikzpicture}

but it doesn't work. Again it doesn't cycle correctly (that's why I'm suspicious about \newcount).

Which is the best way to achieve this? May be another completely different method?

By the way, is there any big question/community wiki about calendars? May be it would be good to open one.

Answer 1

I replaced your if-if-if-if construct with a simple \ifcase test. \moon works just fine now. Though the actual problem was another one. The counter assignments \global\advance\<counter> by 1 should be finished with a \relax. This also applies to the \ifnum but in this instance, it is not needed as math-mode is introduces right away. Without the \relax TeX might find more digits and swallows more than it should. Interestingly, putting \else on the next line does work, too.

Test the following code by subsequently restoring your original macro (no \relax/\else on the same line) and output a full line of \moon \moon \moon \moon \moon \moon.

\def\moon{%
\ifnum\mooncounter=1%
    $\newmoon$\global\advance\mooncounter by 1
  \else
    \ifnum\mooncounter=2% 
        $\rightmoon$\global\advance\mooncounter by 1\relax\else
        \ifnum\mooncounter=3% 
            $\fullmoon$\global\advance\mooncounter by 1
          \else
            \ifnum\mooncounter=4% 
                $\leftmoon$\global\mooncounter=1
            \fi%
        \fi%
    \fi%
\fi%
}

Anyhow, in this case I find a \ifcase construct much clearer:

\def\moon{%
    \global\advance\mooncounter by 1\relax% needs \mooncounter to start with -1
    \ifcase\mooncounter   $\newmoon$%                             = 0
        \or             $\rightmoon$%                             = 1
        \or              $\fullmoon$%                             = 2
        \or              $\leftmoon$\global\mooncounter=-1\relax% = 3
    \fi%
}

Also, I prepended \moon in the for-each loop with a \noexpand so that is firstly expanded when it is actually typeset.

Code

\documentclass{scrartcl}
\usepackage{mathabx}
\usepackage{tikz}
\usetikzlibrary{calendar}
\usepackage{etoolbox}

\newcount\mooncounter
\def\moonreset{\global\mooncounter=-1\relax}
\moonreset

\def\moon{%
    \global\advance\mooncounter by 1\relax%
    \ifcase\mooncounter $\newmoon$%
        \or             $\rightmoon$%
        \or             $\fullmoon$%
        \or             $\leftmoon$\global\mooncounter=-1\relax%
    \fi%
}

\newcommand*{\listofmoons}[1]{%
    \edef\listmoons{#1}%
    \def\moons{}%
    \foreach \l in \listmoons {%
        \xappto\moons{if (equals = 2012-12-\l) [day text=\noexpand\moon\%d-]}
    }%
}
\begin{document}
\moon \moon
\moonreset

\begin{tikzpicture}
    \calendar [
        dates = 2012-12-1 to 2012-12-last,
        week list,
        day xshift = 3em
        ] if (equals = 2012-12-27,
            equals = 2012-12-2,
            equals = 2012-12-7,
            equals = 2012-12-6,
            equals = 2012-12-8,
            equals = 2012-12-9,
            equals = 2012-12-12) [day text = \moon\%d-];
\end{tikzpicture}

\moonreset
\begin{tikzpicture}
    \listofmoons{2,6,7,8,9,12,27}
    \calendar [
        dates = 2012-12-1 to 2012-12-last,
        week list,
        day xshift = 3em
        ] \moons;
\end{tikzpicture}
\end{document}

Output