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I am trying to add a variable number of fields to a bytefield, inside a TikZ Node. An earlier question (Using foreach to add variable number of rows to a bytefield inside a TikZ node?) gave helpful hints, but I still don't get it to work. So, here a more detailed example.

\documentclass[tikz]{standalone}

\usepackage{bytefield}


\usetikzlibrary{positioning}


\begin{document}


% What I want to achieve, written out without loops:
% (inelegant, does not scale to the large number of nodes
% for which I need this)
\begin{tikzpicture}


\node [draw] (a) {a};
  \node [draw] at (6,0) (b) {b};


\node [below=of a] {
    \begin{bytefield}{8}
      \wordbox{1}{Source: b} 
      \ \wordbox{1}{1} 
      \ \wordbox{1}{2} 
      \ \wordbox{1}{3}
    \end{bytefield}
  };


\node [below=of b] {
    \begin{bytefield}{8}
      \wordbox{1}{Source: a} 
      \ \wordbox{1}{4} 
      \ \wordbox{1}{5}
    \end{bytefield}
  };
\end{tikzpicture}


% What should be a step in the right direction,
% compare https://tex.stackexchange.com/questions/679919/using-foreach-to-add-variable-number-of-rows-to-a-bytefield-inside-a-tikz-node/679923?noredirect=1#comment1687472_679923


\begin{tikzpicture}[wordbox/.code={\\wordbox{1}{#1}}]
  \node {
    \begin{bytefield}{8}
      \wordbox{1}{Source: A} 
      \tikzset{wordbox/.list={1,2,3}}
    \end{bytefield}
  };
\end{tikzpicture}


% How I hope to get it to work, but only get two wordboxes,
% instead of four on the left, three on the right: 
\begin{tikzpicture}[wordbox/.code={\\wordbox{1}{#1}}]


\node [draw] (a) {a};
  \node [draw] at (6,0) (b) {b};


\foreach \n/\fields in {a/{1,2,3},b/{4,5}} {
  \node [below=of \n] {
    \begin{bytefield}{8}
      \wordbox{1}{Source: \n}
      \tikzset{wordbox/.list=\fields}
    \end{bytefield}
  };
  }
\end{tikzpicture}


% An alternative with a foreach inside bytefield does not even compile: 
% \begin{tikzpicture}


%   \node [draw] (a) {a};
%   \node [draw] at (6,0) (b) {b};


%   \foreach \n/\fields in {a/{1,2,3},b/{4,5}} {
%   \node [below=of \n] {
%     \begin{bytefield}{8}
%       \wordbox{1}{Source: \n}
%       \foreach \f in \fields { \ \wordbox{1}{\f} }
%     \end{bytefield}
%   };
%   }
% \end{tikzpicture}


\end{document}

Example figures for the three steps see below.

In the last case, it seems that the list handler does not iterate over the fields? Any way to fix that?

What I want:

What I want

Intermediate step in the right direction?

Intermediate step in the right direction?

What I get:

What I get

Holger Karl
  • 405

1 Answers1

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If you just say /.list=\fields, the macro \fields will be the only element of your list. Internally, this will lead to a loop that looks like

\foreach \ELEMENT in {\fields}

You need to expand \fields at least once before the .list handler should evaluate it. Thus, you need

\tikzset{wordbox/.list/.expand once=\fields}

or

\tikzset{wordbox/.list/.expanded=\fields}

Your second example (with an explicit \foreach loop) leads to problems because it will group each iteration. It would be similar to

\begin{bytefield}{8}
  \wordbox{1}{Source: \n}
  { \\ \wordbox{1}{1} }
  { \\ \wordbox{1}{2} }
  { \\ \wordbox{1}{3} }
\end{bytefield}

which conflicts on how bytefield works internally.

If you're not satisfied with .list (which uses PGFFor's \foreach internally and would allow the ... syntax) you could use for example \int_step_inline:nnn used as such:

% Preamble
\ExplSyntaxOn
\DeclareDocumentCommand{\ForeachInline}{}{\int_step_inline:nnn}
\ExplSyntaxOff

% Document
\begin{tikzpicture}
\node [draw] (a) {a};
\node [draw] at (6,0) (b) {b};


\foreach \n/\st/\en in {a/1/3, b/4/5} {
  \node [below=of \n] {
    \begin{bytefield}{8}
      \wordbox{1}{Source: \n}
      \ForeachInline{\st}{\en}{ \ \wordbox{1}{##1} }
    \end{bytefield}
  };
}
\end{tikzpicture}
Qrrbrbirlbel
  • 119,821