Reading the arguments of my command and using them in the command

Question

My question is about reading and using the arguments of a custom created command using \def.

Let's say I have the command \mytestcommand and I want to read and use it's arguments (optional and mandatory of unknown number)

I have the code:

\documentclass[a4paper,10pt]{article}
\usepackage[utf8]{inputenc}
\usepackage{tikz}

\newcounter{NumOptionalArgFound}
\newcounter{NumMandatoryArgFound}
\xdef\MaxMandArgs{3}


\makeatletter
\def\SearchForOptional{%
   \@ifnextchar[%
   {\FoundOptional}
   {\relax}
}
\def\FoundOptional[#1]{%
   \stepcounter{NumOptionalArgFound}%
   \xdef\curOptArg{#1}%
   \global\expandafter\let\csname OptionalArgument\arabic{NumOptionalArgFound}\endcsname\curOptArg%
   \@ifnextchar[%
   {\FoundOptional}
   {\SearchForMandatory}
}
\def\SearchForMandatory{%
   \@ifnextchar\bgroup%
   {\CheckIfMandatory}
   {\relax}
}
\def\CheckIfMandatory#1{%
   \ifnum\pdf@strcmp{#1}{\bgroup}=0%
      #1%
   \else
      \ifnum\arabic{NumMandatoryArgFound}<\MaxMandArgs%
         \stepcounter{NumMandatoryArgFound}%
         \xdef\curManArg{#1}%
         \global\expandafter\let\csname MandatoryArgument\arabic{NumMandatoryArgFound}\endcsname\curManArg%
         \expandafter\expandafter\expandafter\SearchForMandatory%
      \else
         #1%
      \fi
   \fi
}
\makeatother

\def\mytestcommand{
\xdef\MaxMandArgs{2}
\SearchForOptional
}


\def\printArgs{
\foreach \i in {1,...,\theNumOptionalArgFound}{
Opt Arg \i: \csname OptionalArgument\i\endcsname\par
}

\foreach \i in {1,...,\theNumMandatoryArgFound}{
Mand Arg \i: \csname MandatoryArgument\i\endcsname\par
}
}


\begin{document}

\mytestcommand[Optional 1][Optional Second]{first Mand}{second Mand}{thirdMand}\bgroup noMand \egroup

\printArgs
\end{document}

This code works fine and finds-saves the optional and mandatory arguments of ot. My problem is that if i try to use one of the counters or of the arguments inside the definition of \mytestcommand it fails to find the number or the argument.

More specific, I would like to use \printArgs command inside of \mytestcommand definition... (So I can know I am able to use the arguments inside my command definition).

The problem appears if I change the definition of \mytestcommand to:

\def\mytestcommand{
\xdef\MaxMandArgs{2}
\SearchForOptional
\printArgs
}

Thank's=Thanks

PS: I am looking for a LaTeX2e solution, but LaTeX3 is probably helpful for other users... I would like not to use packages that I know exist for such jobs but if possible, "primary" LaTeX commands like mine...

Answer 1

Add an x to see the problem:

\def\SearchForOptimal{%
   \@ifnextchar[%
   {\FoundOptimal}%
   {x\relax}%
}

The next character in this case is \ and not [. Hence, the 'if false' condition is used, x\relax.

Note that the problem has nothing to do with the use of the arguments. Try

\def\mytestcommand{%
\xdef\MaxMandArgs{2}%
\SearchForOptimal
x
}

for comparison. The way you have \SearchForOptimal written, it has to be the last thing in \mytestcommand.

Answer 2

Something like this.

\documentclass[a4paper,10pt]{article}
\usepackage[utf8]{inputenc}
\usepackage{tikz}

\newcounter{NumOptionalArgFound}
\newcounter{NumMandatoryArgFound}

\newcommand\MaxMandArgs{3}% default value

\makeatletter

\newcommand\SearchForArguments {%
   \setcounter{NumOptionalArgFound}{0}%
   \setcounter{NumMandatoryArgFound}{0}%
   \@SearchForOptional
}

% fetching optional arguments

\newcommand\@SearchForOptional{%
    \kernel@ifnextchar[\@FoundOptional\@SearchForMandatory
}

\def\@FoundOptional[#1]{%
   \stepcounter{NumOptionalArgFound}%
   \global\@namedef{OptionalArgument\arabic{NumOptionalArgFound}}{#1}%
   \@SearchForOptional
}

% fetching mandatory arguments

% I do not quite understand this \bgroup business but aiming
% to be close to OP. It actually complicates things a lot because
% one can not use a \futurelet to distinguish \bgroup from {

\newcommand\@SearchForMandatory[1]{%
    \edef\@tempKola{\detokenize{#1}}%
    \edef\@tempKolb{\detokenize{\bgroup}}%
    \ifx\@tempKola\@tempKolb
      \expandafter\@firstofone
    \else
      \ifnum\value{NumMandatoryArgFound}<\MaxMandArgs %<- must leave a space
       \stepcounter{NumMandatoryArgFound}%
       \expandafter\expandafter\expandafter\@GetMandatoryAndGoOn
      \else
       \expandafter\expandafter\expandafter\@firstofone
      \fi
    \fi {#1}%
}

\newcommand\@GetMandatoryAndGoOn[1]{%
    \global\@namedef{MandatoryArgument\arabic{NumMandatoryArgFound}}{#1}%
    \@SearchForMandatory
}
\makeatother

\newcommand\printArgs{{\color{blue}%
Value of MaxMandArgs: \MaxMandArgs

\ifnum\value{NumOptionalArgFound}>0
  \foreach \i in {1,...,\theNumOptionalArgFound}{%
  Opt Arg \i: \csname OptionalArgument\i\endcsname\par
}\fi

\ifnum\value{NumMandatoryArgFound}>0
  \foreach \i in {1,...,\theNumMandatoryArgFound}{%
  Mand Arg \i: \csname MandatoryArgument\i\endcsname\par
}\fi
}}

\newcommand\mytestcommand[1]{\gdef\MaxMandArgs{#1}\SearchForArguments}

\begin{document}

\mytestcommand{2}[Optional 1][Optional Second]{first Mand}{second Mand}{third Mand}\bgroup noMand \egroup

\printArgs

\mytestcommand{3}[O1][O2][O3][O4]{M1}{M2}{M3}{M4}{M5}\bgroup STOP\egroup

\printArgs

\end{document}

What is in black is what has not been considered part of the thing.

One could modify the macros above to not swallow the arguments it identifies as either optional or mandatory.

There is a powerful package called xparse which seems indicated here.

And with

\mytestcommand{6}[O1][O2][O3][O4]{M1}{M2}{M3}{M4}{M5}\bgroup STOP\egroup

\printArgs