nested environments deplete my tex stack

Question

I want to create an environment for drawing same-styled derivation trees in my document. I sometimes want this environment placed in a certain float, but sometimes I want a different one (like using a landscape-rotated page or whatever), so I split my favorite float to be an outer environment and my inner float to be the tikz tree. unfortunately, this created a recursion in tex that exploded my stack. Here's a code example:

\documentclass[12pt]{article}    
\usepackage{environ}
\usepackage{tikz}

\NewEnviron{AST}{
\begin{tikzpicture}
        [
                sibling distance = 6em,
                level distance = 6em,
                align = center,
                grow' = right,
                every node/.style = {shape=rectangle, rounded corners,
                        draw, align=center,
                        top color=white, bottom color=blue!20},
                leaf/.style = {font=\ttfamily}
        ]
        \BODY\
\end{tikzpicture}
        }

% #1 is short name for figure
% #2 is long name for figure
\NewEnviron{ASTfig}[2]{
\begin{figure}[hbp]
  \begin{center}
    \begin{AST}
        \BODY\
    \end{AST}
  \end{center}
\caption[AST - #1]{Abstract Syntax Tree - #2}
\end{figure}
}

\begin{document}
\begin{ASTfig}{shambalulu}{bambashushu}
\node {root}
        child { node {node}
                child { node [leaf] {leafy} }
                child { node [leaf] {mcleaf} }
                }
        };
\end{ASTfig}
\end{document}

I guess it's because tex is trying to replace \BODY\ with \BODY\ ad infinitum. I flipped through the documentation and tried using the \environbodyname command, but it changed \BODY on both cases and did not solve the problem.

what am I missing?

score 1 · Answer 1 · edited Jun 10 '20 at 12:32

Not exactly sure what you are trying to do, but it seems that \AST should be a macro , not an environment:

Reference:

Should I use center or centering for figures and tables?

Code:

\documentclass[12pt]{article}    
\usepackage{environ}
\usepackage{tikz}
\newcommand{\AST}[1]{%
\begin{tikzpicture}
        [
                sibling distance = 6em,
                level distance = 6em,
                align = center,
                grow' = right,
                every node/.style = {shape=rectangle, rounded corners,
                        draw, align=center,
                        top color=white, bottom color=blue!20},
                leaf/.style = {font=\ttfamily}
        ]
        #1
\end{tikzpicture}%
}
% #1 is short name for figure
% #2 is long name for figure
\NewEnviron{ASTfig}[2]{%
\begin{figure}[hbp]
  \centering
  \AST{\BODY}
\caption[AST - #1]{Abstract Syntax Tree - #2}
\end{figure}%
}
\begin{document}
\begin{ASTfig}{shambalulu}{bambashushu}
\node {root}
        child { node {node}
                child { node [leaf] {leafy} }
                child { node [leaf] {mcleaf} }
                }
        ;
\end{ASTfig}
\end{document}

on what do you base the choice of defining AST as a macro and not an environments? what qualifies for a good environment? — Nailo, May 28 '18 at 17:50
@Nailo: Good question. I don't really have a good reason that I can articulate right now. Just "seemed" that it should be to me. — Peter Grill, May 28 '18 at 21:36

score 0 · Accepted Answer · answered May 26 '18 at 09:57

The inner \BODY in \begin{AST}\BODY\end{ast} needs to be renamed before environment AST ist called, e.g.:

\documentclass[12pt]{article}
\usepackage{environ}
\usepackage{tikz}

\NewEnviron{AST}{%
  \begin{tikzpicture}
    [
      sibling distance = 6em,
      level distance = 6em,
      align = center,
      grow' = right,
      every node/.style = {
        shape=rectangle, rounded corners,
        draw, align=center,
        top color=white, bottom color=blue!20},
      leaf/.style = {font=\ttfamily}
    ]
    \BODY
  \end{tikzpicture}%
}

% #1 is short name for figure
% #2 is long name for figure
\NewEnviron{ASTfig}[2]{%
  \begin{figure}[hbp]
    \centering
    \let\INNERBODY\BODY
    \begin{AST}
      \INNERBODY
    \end{AST}
    \caption[AST - #1]{Abstract Syntax Tree - #2}
  \end{figure}%
}

\begin{document}
\begin{ASTfig}{shambalulu}{bambashushu}
\node {root}
  child {
    node {node}
    child { node [leaf] {leafy} }
    child { node [leaf] {mcleaf} }
  };
\end{ASTfig}
\end{document}

Additional remarks:

\centering instead of environment center is preferred, because environment center adds additional vertical spacing. But figure already adds vertical space.
There is no point in using the backslash after the command in \BODY\. The environment ends anyway and forcing a space here makes no sense.
End of lines usually adds a space. The example comments some line ends in the definitions to prevent leaking spaces.

score 0 · Answer 3 · answered May 26 '18 at 18:08

You don't need \NewEnviron for the inner environment.

I suggest to use xparse, so you can avoid \NewEnviron also for the outer one.

\documentclass[12pt]{article}    
\usepackage{xparse}
\usepackage{tikz}

\NewDocumentEnvironment{AST}{}
 {%
  \begin{tikzpicture}[
    sibling distance = 6em,
    level distance = 6em,
    align = center,
    grow' = right,
    every node/.style = {
      shape=rectangle,
      rounded corners,
      draw,
      align=center,
      top color=white,
      bottom color=blue!20
    },
      leaf/.style = {font=\ttfamily}
  ]
 }
 {\end{tikzpicture}}

% #1 is short name for figure
% #2 is long name for figure
\NewDocumentEnvironment{ASTfig}{O{#2}m}
 {%
  \begin{figure}[hbp]
  \centering
  \begin{AST}
 }
 {%
  \end{AST}
  \caption[AST - #1]{Abstract Syntax Tree - #2}
  \end{figure}
 }

\begin{document}
\begin{ASTfig}[shambalulu]{bambashushu}
  \node {root}
    child {
      node {node}
      child { node [leaf] {leafy} }
      child { node [leaf] {mcleaf} }
    };
\end{ASTfig}
\end{document}

The syntax is a bit different, but in my opinion more convenient. You call

\begin{ASTfig}{xyz}

if the short caption is equal to the long caption; you call

\begin{ASTfig}[short]{long}

if they're different.

nested environments deplete my tex stack

3 Answers3

Reference:

Code: