# tikzpicture has a node whose text is a tree: unevenly formatting

I want to typeset a picture similar to the following one, using tikz.

For that purpose I have written the following latex document

\documentclass{minimal}
\usepackage{tikz}
\usetikzlibrary{chains}

\begin{document}

\begin{tikzpicture}[
level distance=10mm,
op/.style={circle,draw,fill=red!20},
leaf/.style={circle,fill=blue!20,font=\ttfamily},
]
\node (in) [fill=green!10] {\texttt{1 + 2*3}};
\node (out) [fill=green!10,right=30mm of in] {
\tikz{
\node [op] {$+$}
child { node [leaf] {1} }
child { node [op] {$\times$}
child { node [leaf] {2} }
child { node [leaf] {3} }};
}
};
\draw[->] (in) -- node [above] {\emph{parsing}} (out);
\end{tikzpicture}

\end{document}


which gives me the output

Notice that in the tree, the left and right edges from each node are not symmetric: the left one is shorter than the right one. When the same tree is drawn outside of the out node, they are symmetric.

Why am I getting this effect, and how to fix this issue?

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## 1 Answer

Say it backwards:

\begin{tikzpicture}[
level distance=10mm,
op/.style={circle,draw,fill=red!20},
leaf/.style={circle,fill=blue!20,font=\ttfamily},
]
\node (out) [fill=green!10] {
\tikz{
\node [op] {$+$}
child { node [leaf] {1} }
child { node [op] {$\times$}
child { node [leaf] {2} }
child { node [leaf] {3} }};
}
};
\node (in) [fill=green!10,left=30mm of out] {\texttt{1 + 2*3}};
\draw[->] (in) -- node [above] {\emph{parsing}} (out);
\end{tikzpicture}


I really don't know why it works.

-
Yep, seems that the right=of something interferes with the layout of the tree nodes. I'd also really like to know why? –  Count Zero Nov 10 '11 at 18:42
In fact the right=of something option enabled by the chains library seems to be the problem. Using node distance=50mm,right of=in instead of right=30mm of in in the out node gives a correct layout for the tree. –  Romildo Nov 10 '11 at 20:14
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