Creating and using commands/counters which name depends on other counter

Question

I would like to know how can I use a counter for defining other new counters.

Something like this:

\newcounter{foo}
\stepcounter{foo}

%% Perhaps more increments, this depends of the user.

%% And now, to create a new counter and command from foo.

\newcounter{\csname foofoo\thefoo\endcsname}
\def\csname mydyndef\thefoo\endcsname{definition...}

For example, with foo = 5, to create the counter foofoo5 and the command \mydyndef5.

And of course, to use it now:

This is my example \csname mydyndef\thefoo\endcsname,
with counter \csname thefoofoo\thefoo \endcsname.

But, of course, nothing of this works for me. And that is the question:

How can I achieve this?

This problem arises from searching a pure manual solution to this question: New list environment: automatic enumeration with "a posteriori" format, creating a counter (label@counterx) and saving the format in a command (\label@formatx) for each new depth (controlled by list@depth counter):

\newenvironment{labelist}{%%%

  \stepcounter{list@depth} %% Actual depth

  \ifnumcomp{\value{list@depth}}{=}{1} {
     \newcounter{label@counter1}
     \setcounter{label@coutner1}{0}

     \def\label@format1{\Alph{label@counter1}}

     \begin{list}{ \textbf{(\label@format1)}  }
                 { \usecounter{label@counter1 }
  }{
    %% Similar to the first case, but replacing 1 with the actual depth.
  }
}{
   %% Other code not-important here.
}

Answer 1

• \newcounter does not take a macro token, but a simple name:

  \newcounter{foofoo\thefoo}
  

• \def\csname redefines \csname, you need \expandafter:

  \expandafter\def\csname mydyndef\thefoo\endcsname{definition ...}