Use the counter value as an argument

Question

Do you know a simple way to use the current counter value to call the argument in a macro?

In myPackage I have this

Note: I have the for loop defined as

% \forloop[step]{counter}{initial_value}{conditional}{code_block}

The problem is in the following code

\newcounter{foo}
\newenvironment{myEnvironment}[1]{
    \newcommand{\myLocalMacro}[#1]{% number of arguments depends on the value inserted in myEnvironment (this works fine)
        \forloop[1]{foo}{1}{\numexpr\value{foo}-1<#1}{
            ##\value{foo} % HERE I need to return ##1 if foo is 1, ##2 if foo is 2 etc. (this doesn't work)
            - % some separator
        }%end forloop
    }%end myLocalMacro
}
{}%end myEnvironment

I tested the variable number of arguments in \myLocalMacro and it works.

I also tested the nesting of arguments in \forloop - writing ##1, ##2 etc. inside the for loop gives 1st and 2nd value. Now I need it dependent on foo counter.

The main document will look like this

\documentclass{article}
\usepackage{myPackage}
\begin{document}
\begin{myEnvironment}{7}
    \myLocalMacro{F}{O}{O}{B}{A}{R}{1} % this separation into arguments will be written manually
    \myLocalMacro{F}{O}{O}{B}{A}{R}{2}
    \myLocalMacro{F}{O}{O}{B}{A}{R}{3}
\end{myEnvironment}

or

\begin{myEnvironment}{3}
    \myLocalMacro{T}{e}{X}
    \myLocalMacro{a}{b}{c}
\end{myEnvironment}


\end{document}

The expected output should look like

F - O - O - B - A - R - 1 -

F - O - O - B - A - R - 2 -

F - O - O - B - A - R - 3 -

or

T - e - X -

a - b - c -

Well, this is only an example, the real formating will be more complex, which is why I defined an environment for it and don't do it manually for every single character.

Thanks.

Answer 1

Your proposed definition can't work, because TeX makes no expansion to the tokens in the replacement text of a macro and #1 must be literal: it can't be given as #\value{counter}. There are some tricks for making this possible, but I don't think they would help in your case.

Here's something that might be what you're looking for:

\documentclass{article}

\makeatletter
\newenvironment{myEnvironment}[1]
 {\let\myEnv@Temp#1\relax}
 {}

\newcommand\myLocalMacro[1]{%
  \@tfor\next:=#1\do{\expandafter\myEnv@Temp\expandafter{\next}}%
}
\makeatother

\newcommand{\addhyphen}[1]{#1 - }
\newcommand{\addcomma}[1]{#1, }

\begin{document}
\begin{myEnvironment}{\addhyphen}
\myLocalMacro{FOOBAR1}\par
\myLocalMacro{FOOBAR2}\par
\myLocalMacro{FOOBAR3}\par
\end{myEnvironment}

\begin{myEnvironment}{\addcomma}
\myLocalMacro{TeX}\par
\myLocalMacro{abc}\par
\end{myEnvironment}

\end{document}

The argument to myEnvironment is the formatting macro which is applied to every token in the argument to \myLocalMacro.

A different implementation that doesn't require to define auxiliary macros:

\documentclass{article}

\makeatletter
\newenvironment{myEnvironment}[1]
 {\renewcommand\myEnv@Temp[1]{#1}}
 {}

\newcommand\myEnv@Temp{} % initialize

\newcommand\myLocalMacro[1]{%
  \@tfor\next:=#1\do{\expandafter\myEnv@Temp\expandafter{\next}}%
}
\makeatother

\begin{document}
\begin{myEnvironment}{#1 - }
\myLocalMacro{FOOBAR1}\par
\myLocalMacro{FOOBAR2}\par
\myLocalMacro{FOOBAR3}\par
\end{myEnvironment}

\begin{myEnvironment}{#1, }
\myLocalMacro{TeX}\par
\myLocalMacro{abc}\par
\end{myEnvironment}

\end{document}

The argument to myEnvironment is the formatting you want to apply to each token.

If you want to preserve spaces, you need a more complex approach; here's a straightforward way with expl3:

\documentclass{article}
\usepackage{xparse}

\ExplSyntaxOn
\NewDocumentEnvironment{myEnvironment}{m}
 {
  \cs_set:Nn \pavlik_myenv_temp:n { #1 }
 }
 {
 }

\NewDocumentCommand\myLocalMacro{m}
 {
  \pavlik_myenv_local:n { #1 }
 }

\tl_new:N \l__pavlik_myenv_items_tl

\cs_new_protected:Nn \pavlik_myenv_local:n
 {
  \tl_set:Nn \l__pavlik_myenv_items_tl { #1 }
  \tl_replace_all:Nnn \l__pavlik_myenv_items_tl { ~ } { \c_space_tl } % preserve spaces
  \tl_map_inline:Nn \l__pavlik_myenv_items_tl
   {
    \pavlik_myenv_temp:n { ##1 }
   }
 }
\ExplSyntaxOff

\begin{document}
\begin{myEnvironment}{#1 - }
\myLocalMacro{FOO BAR1}\par
\myLocalMacro{FOOBAR2}\par
\myLocalMacro{FOOBAR3}\par
\end{myEnvironment}

\begin{myEnvironment}{#1, }
\myLocalMacro{TeX}\par
\myLocalMacro{abc}\par
\end{myEnvironment}

\end{document}

Here \tl_map_inline:Nn is the analog of \@tfor; before applying it, we change all spaces in the argument with \c_space_tl, whose expansion is a space.