[Tex/LaTex] How to pass two arguments to a newcommand or macro

expansionmacrosparameters

I would first like to thank everyone who contributes on Stack Exchange as they have been an enormous help for everything LaTeX. I have searched all over SE for a solution to this current problem and yet haven't found a solution. Here is my project:

I am making a booklet for the singing of Vespers according to the Traditional rite using the Gregorio project and LuaLatex. Some pdf examples of the work already accomplished can be found here:

http://docs.sspx.org.za/index.php/s/1LRq234nkQGavAW

The layout is done quasi-automatically with the simple modification of the filenames for the import of the antiphons, etc. I am preparing to put all the source code online so that anyone else can use it and provide other translations [English and Polish I have done myself, but others can provide in more languages]. I would like to clean up the source code a bit however and make it as easy as possible for others to contribute. Part of this would be a simple macro to determine which Sunday of the Liturgical Year to typeset.

For those who know the Traditional Latin Rite, the antiphon changes each Sunday, but the overall structure of Vespers stays the same. What I would like to do is have the option of simply specifying the Sunday of the year as a variable and then have the LaTeX calculate the rest. However I am having a lot of trouble in passing the parameters of one command to another.

Here is my current working example of how to choose the antiphon (with imaginary cases to make the example shorter, the real macro has 52 choices, and what are given are actually the names of the .gabc files in another directory). I am using the package xstring which has the \IfEqCase command which I can nest in the following way :

\newcommand{\whichantifon}[2]{%
   \IfEqCase{#1}{%
     {advent}{\IfEqCase{#2}{%
       {i}{First Sunday of Advent, Magnificat-4a}
       {ii}{Second Sunday of Advent, Magnificat-6F}
      }}% end advent cases
     {pentecost}{\IfEqCase{#2}{%
      {i}{First Sunday after Pentecost, Magnifcat-1d}
      {ii}{Second Sunday after Pentecost, Magnifcat-3a}
      }}% end pentecost cases
  }% end choose instruction
}%end command

With this macro I can do something like this to pull out the proper antiphon and mode:

\whichantifon{advent}{i}

What I would like to do is pass the results of this choice to another macro which actually does the typesetting of the chant, using the two arguments from this choice:

\canticum{\whichantifon{advent}{i}}

In order to get a working example I put a simple \def like this one that does a minimum of typesetting:

\def\canticum#1, #2{%
    This is the #1, and Magnificat #2}%

The idea being that the simple comma which is part of the expansion of the \whichantifon will then be the separator for the two arguments for this \canticum, thinking this to be an elegant solution as otherwise I would have to have two very lengthly choice macros. However it doesn't work, or rather it only works partially.

If I have the following document with the above macros defined, I can get the output of the following:

\whichantifon{advent}{i}

Which gives this, so this part works very well:

First Sunday of Advent, Magnificat-4a

However if I try the simple \canticum as above :

\canticum{\whichantifon{advent}{i}}

I get the following error:

   ERROR: Paragraph ended before \canticum was complete.

Apparently 'A blank line occured in a command argument that shouldn't contain one'. However if I just copy/paste the output of the first macro to the \canticum it works just fine. I have looked all over SE for the \expandafter and other tricks but nothing works. I have even tried using string separators and other packages, but that ended up with even more complications and no solution.

I have always understood LaTeX to be simply a sort of macro expander or substitution language. However it seems not to substitute at certain times or in ways that are not at all intuitive. For instance, when does the argument to \def get expanded? before or after its own evaluation? It would seem to need to evaluate the arguments before the definition, but it doesn't seem to work in this way.

What I really want to do is have a function that returns two arguments to be used as the input for another function. This of course is not a very proper function so my approach is probably incorrect.

The real difficulty is that each Sunday has two pieces of information, the antiphon and the tone of the Magnificat, and these two pieces of information determine what gets typeset in the document. The contributors would ideally only have to provide one piece of information [which Sunday] while the latex would provide the rest (as the actual files and tones would already be in the project folder).

Any sort of help or links to resolve this difficulty, or even different approaches would be most welcome. If it would helpful I can post a link to the git repo as a 'work in progress'.

Thank you for at least reading this question!

Best Answer

[please always provide a test file rather than just a fragment]

The easiest way is to pass the formatting command as an argument to your selector, I made it optional here

\newcommand\canticum[2]{%
    This is the #1, and Magnificat #2}%

\newcommand{\whichantifon}[3][\canticum]{%
   \IfEqCase{#2}{%
     {advent}{\IfEqCase{#3}{%
       {i}{#1{First Sunday of Advent}{Magnificat-4a}}
       {ii}{#1{Second Sunday of Advent}{Magnificat-6F}}
      }}% end advent cases
     {pentecost}{\IfEqCase{#3}{%
      {i}{#1{First Sunday after Pentecost}{Magnifcat-1d}}
      {ii}{#1{Second Sunday after Pentecost}{Magnifcat-3a}}
      }}% end pentecost cases
  }% end choose instruction
}%end command

so by default

\whichantifon{advent}{i}

will use \canticum but you can pass in any other two argument command instead

\newcommand\zzz[2]{\fbox{#1}---\fbox{#2}}
\whichantifon[\zzz]{advent}{i}

Related Solutions

[Tex/LaTex] A macro with either one or two arguments

I'd use the xparse package to do this, as everything is then 'pre-packaged':

\documentclass{article}
\usepackage{color,xparse}
\NewDocumentCommand\MyTextColor{m+g}{%
  \IfNoValueTF{#2}
    {\color{#1}}
    {\textcolor{#1}{#2}}%
}
\begin{document}
\MyTextColor{green}{stuff}

\MyTextColor{red} Some text
\end{document}

The same can of course be done using \@ifnextchar

\documentclass{article}
\usepackage{color}
\makeatletter
\newcommand*\MyTextColor[1]{%
  \@ifnextchar\bgroup
    {\textcolor{#1}}
    {\color{#1}}%
}
\makeatother
\begin{document}
\MyTextColor{green}{stuff}

\MyTextColor{red} Some text
\end{document}

The key point is that you need to look for { using \bgroup rather than trying to use it directly (as it is the begin-group character).

To explain how the \@ifnextchar part deals with the need for either 1 or 2 arguments, what happens in my second approach is that

\newcommand*\MyTextColor[1]{%

defines a macro which absorbs one argument. So:

\MyTextColor{red}{stuff}

absorbs red as #1 and leaves {stuff} in the input stream, while

\MyTextColor{red} other stuff

also absorbs red as #1 and leaves other stuff in the input stream. We now apply \@ifnextchar, which 'peeks' at the next token without absorbing it. The test reads

  \@ifnextchar\bgroup
    {\textcolor{#1}}
    {\color{#1}}%

and so depending on the result, either \textcolor{red} or \color{red} is inserted into the input stream. Thus we end up with either

\textcolor{red}{stuff}

\color{red} other stuff

which means that \textcolor will get the required two arguments, while \color only gets one. The key is that {red} is reinserted into the input after either \textcolor or \color.

Although it is not directly related to the question, a few notes on the xparse approach may be useful. When using the xparse package, arguments are described by letter, with m representing a mandatory argument and g representing an optional argument in braces (i.e. an optional TeX group). A + before the letter allows that argument to accept paragraph tokens, so in my definition the first argument cannot (it's supposed to be the name of a colour), while the second one can (it is arbitrary text).

The g argument returns a special token (\NoValue) if the optional argument was not present at all. If a default value was wanted, I'd have used G{<default>}. The same approach applies to standard LaTeX optional arguments, which are represented as o or O, depending on whether a default value is required. I have tested for \NoValue with the test \IfNoValueTF; \IfNoValueT and \IfNoValueT are also available.

[Tex/LaTex] Passing nodes as parameters to a macro in TikZ

I assume you want to keep the node definitions you pass as arguments independent of what happens inside the macro (so you don't want to explicitly use left of=diamond.west in the node definition). In order to achieve this, you can wrap the nodes passed in scope environments inside the macro and "inject" the positioning options, or, as Martin Scharrer suggests, use \tikzset inside curly braces to set the options locally:

\documentclass{article}

\usepackage{tikz}
\usetikzlibrary{shapes,positioning,fit}

\newcommand{\diamondconn}[3]{

  \node[diamond, draw, inner sep=2pt] (diamond) { #1 };
  {\tikzset{every node/.style={left=0pt of diamond.west}} #2 }
  {\tikzset{every node/.style={right=0pt of diamond.east}} #3 } 
}

\begin{document}

\begin{tikzpicture}
  \diamondconn{conn}{
    \node[draw, rectangle] { foo };
  }{
    \node[draw, circle] { bar };
  }
\end{tikzpicture}

\end{document}

Best Answer

Related Solutions

[Tex/LaTex] A macro with either one or two arguments

[Tex/LaTex] Passing nodes as parameters to a macro in TikZ

Related Question