Store counter in list

Question

I have some sort of a list and want to add the actual enumi-count to that list. I assume, that in my problem I'm somehow just storing the pointer to that counter and not the value itself, so even the stored counter-value increases as the counter itself increases. I even tried definining a tempcounter I set to the value of the enumi-counter, but I've read somewheere, that I should expand the counter, so I'm clueless what to do.

\documentclass{scrartcl}
\usepackage{ifthen}

\def\aliste{}
\def\zaliste#1\relax{\gdef\aliste{#1}}
\def\addtoaliste#1{%
  \ifthenelse{\equal{\aliste}{}}{%
    \expandafter\zaliste\aliste#1\relax
  }{\expandafter\zaliste\aliste,#1\relax
  }%
}

\begin{document}
    Value: \aliste\\
    \addtoaliste{A}
    Value: \aliste\\ %Returns A
    \begin{enumerate}
        \item 
            Output: \arabic{enumi}\\ %is 1
            \addtoaliste{\arabic{enumi}} %adds 1 to the list
            \aliste %returns A,1
        \item 
            Output: \arabic{enumi}\\ %is 2
            \addtoaliste{\arabic{enumi}} %shall add 2 to the list
            Value: \aliste %returns A,2,2
    \end{enumerate}
    Value: \aliste %returns A,2,2
\end{document}

Werner · Accepted Answer · 2019-09-24T15:05:42.077

I remove ifthen (since it's considered obsolete) and use a regular \ifx\aliste\relax test to see what the value of \aliste is before adding something. Note that the addition uses \xdef - a expandable version of \gdef (which is a global definition). The global definition is required in order for the list additions to survive outside the scoped (enumerate) environment.

\documentclass{article}

\let\aliste\relax
\def\addtoaliste#1{%
  \ifx\aliste\relax
    \xdef\aliste{#1}% List is empty. Just add #1
  \else
    \xdef\aliste{\aliste,#1}% List is non-empty. Add old list, comma and #1
  \fi
}

\begin{document}
Value: \aliste \\

\addtoaliste{A}

Value: \aliste \\ % returns A

\begin{enumerate}
  \item 
    Output: \arabic{enumi} \\ % is 1
    \addtoaliste{\arabic{enumi}} % adds 1 to the list
    Value: \aliste % returns A,1
  \item 
    Output: \arabic{enumi} \\ % is 2
    \addtoaliste{\arabic{enumi}} % shall add 2 to the list
    Value: \aliste % returns A,1,2
\end{enumerate}

Value: \aliste % returns A,1,2

\end{document}

It's working, only if the list is not empty when adding the first value in the enumerate-environment. Try comment out the 3 lines before the enumerate. Solved it by changing the other gdef to xdef too — WuaghhhhXMA, Sep 24 '19 at 06:57

Store counter in list

1 Answers1