如果我有一个 tikzpictures 块，则文档会编译。参见代码：
\documentclass[12pt]{article}
\usepackage{amssymb}
\usepackage{amsmath}
\usepackage{graphicx}
\graphicspath{{images/}}
\usepackage{xcolor}
\usepackage{pgfplots}
\usepackage{mdframed}
\usepackage{amsthm}
\usepackage{framed}
\colorlet{shadecolor}{gray!50}
\begin{document}
\begin{mdframed} [everyline=true, splitbottomskip = 10mm, splittopskip = 10mm, innertopmargin = 10mm, innerbottommargin = 10mm]
\noindent \textit{\textbf{Example(s) 3.3 and 3.4:}} Consider two games modeled by the following figures. \vspace{3mm}
\begin{center}
\usetikzlibrary{positioning} \begin{tikzpicture}[xscale=6, yscale=8,>=stealth]
\tikzstyle{v}=[circle, minimum size=1mm,draw,thick] \node[v]
(a) {$a$}; \node[] (x)
[right=of a]{}; \node[v] (c) [below=of x]{$c$}; \draw[thick,->] (a) to node {}(c);
\node[] (y)
[left=of a]{}; \node[v] (b) [below=of y]{$b$}; \draw[thick,->] (a) to node {}(b);
\draw[thick,->] (b) to node {}(c);
\node[v] (e) [below=of c]{$e$};
\node[v] (d) [below=of b]{$d$};
\draw[thick,->] (b) to node {}(d);
\draw[thick,->] (c) to node {}(e);
\draw[thick,->] (c) to node {}(d);
\end{tikzpicture} \vspace{3mm}
\textit{Figure 3.5} \vspace{3mm}
\begin{tikzpicture}[xscale=6, yscale=8,>=stealth]
\tikzstyle{v}=[circle, minimum size=1mm,draw,thick] \node[v]
(a) {$a$}; \node[] (x)
[right=of a]{}; \node[v] (c) [below=of x]{$c$}; \draw[thick,->] (a) to node {}(c);
\node[] (y)
[left=of a]{}; \node[v] (b) [below=of y]{$b$}; \draw[thick,->] (a) to node {}(b);
\draw[thick,->] (b) to node {}(c);
\node[v] (e) [below=of c]{$e$};
\node[v] (d) [below=of b]{$d$};
\node[v] (f) [right=of c]{$f$};
\node[v] (i) [left=of d]{$i$};
\node[v] (h) [below=of e]{$h$};
\draw[thick,->] (d) to node {}(f);
\draw[thick,->] (e) to node {}(h);
\draw[thick,->] (h) to node {}(f);
\draw[thick,->] (b) to node {}(i);
\draw[thick,->] (i) to node {}(c);
\draw[thick,->] (d) to node {}(h);
\draw[thick,->] (b) to node {}(d);
\draw[thick,->] (a) to node {}(e);
\draw[thick,->] (c) to node {}(d);
\draw[thick,->] (e) to node {}(d);
\draw[thick,->] (i) to node {}(d);
\end{tikzpicture} \vspace{3mm}
\textit{Figure 3.6}
\end{center}
\end{mdframed} \vspace{5mm}
\end{document}
如果我在 tikzpictures 块后添加文本，然后添加新的 tikzpicture 环境，则该文档不会编译。请参阅代码：
\documentclass[12pt]{article}
\usepackage{amssymb}
\usepackage{amsmath}
\usepackage{graphicx}
\graphicspath{{images/}}
\usepackage{xcolor}
\usepackage{pgfplots}
\usepackage{mdframed}
\usepackage{amsthm}
\usepackage{framed}
\colorlet{shadecolor}{gray!50}
\begin{document}
\begin{mdframed} [everyline=true, splitbottomskip = 10mm, splittopskip = 10mm, innertopmargin = 10mm, innerbottommargin = 10mm]
\noindent \textit{\textbf{Example(s) 3.3 and 3.4:}} Consider two games modeled by the following figures. \vspace{3mm}
\begin{center}
\usetikzlibrary{positioning} \begin{tikzpicture}[xscale=6, yscale=8,>=stealth]
\tikzstyle{v}=[circle, minimum size=1mm,draw,thick] \node[v]
(a) {$a$}; \node[] (x)
[right=of a]{}; \node[v] (c) [below=of x]{$c$}; \draw[thick,->] (a) to node {}(c);
\node[] (y)
[left=of a]{}; \node[v] (b) [below=of y]{$b$}; \draw[thick,->] (a) to node {}(b);
\draw[thick,->] (b) to node {}(c);
\node[v] (e) [below=of c]{$e$};
\node[v] (d) [below=of b]{$d$};
\draw[thick,->] (b) to node {}(d);
\draw[thick,->] (c) to node {}(e);
\draw[thick,->] (c) to node {}(d);
\end{tikzpicture} \vspace{3mm}
\textit{Figure 3.5} \vspace{3mm}
\begin{tikzpicture}[xscale=6, yscale=8,>=stealth]
\tikzstyle{v}=[circle, minimum size=1mm,draw,thick] \node[v]
(a) {$a$}; \node[] (x)
[right=of a]{}; \node[v] (c) [below=of x]{$c$}; \draw[thick,->] (a) to node {}(c);
\node[] (y)
[left=of a]{}; \node[v] (b) [below=of y]{$b$}; \draw[thick,->] (a) to node {}(b);
\draw[thick,->] (b) to node {}(c);
\node[v] (e) [below=of c]{$e$};
\node[v] (d) [below=of b]{$d$};
\node[v] (f) [right=of c]{$f$};
\node[v] (i) [left=of d]{$i$};
\node[v] (h) [below=of e]{$h$};
\draw[thick,->] (d) to node {}(f);
\draw[thick,->] (e) to node {}(h);
\draw[thick,->] (h) to node {}(f);
\draw[thick,->] (b) to node {}(i);
\draw[thick,->] (i) to node {}(c);
\draw[thick,->] (d) to node {}(h);
\draw[thick,->] (b) to node {}(d);
\draw[thick,->] (a) to node {}(e);
\draw[thick,->] (c) to node {}(d);
\draw[thick,->] (e) to node {}(d);
\draw[thick,->] (i) to node {}(d);
\end{tikzpicture} \vspace{3mm}
\textit{Figure 3.6}
\end{center}
\end{mdframed} \vspace{5mm}
text stuff
\begin{tikzpicture}[xscale=6, yscale=8,>=stealth]
\tikzstyle{v}=[circle, minimum size=1mm,draw,thick] \node[v]
(a) {$a$}; \node[] (x)
[right=of a]{}; \node[v] (c) [below=of x]{$c$}; \draw[thick,->] (a) to node {}(c);
\node[] (y)
[left=of a]{}; \node[v] (b) [below=of y]{$b$}; \draw[thick,->] (a) to node {}(b);
\draw[thick,->] (b) to node {}(c);
\node[v] (e) [below=of c]{$e$};
\node[v] (d) [below=of b]{$d$};
\node[v] (f) [right=of c]{$f$};
\node[v] (i) [left=of d]{$i$};
\node[v] (h) [below=of e]{$h$};
\draw[thick,->] (d) to node {}(f);
\draw[thick,->] (e) to node {}(h);
\draw[thick,->] (h) to node {}(f);
\draw[thick,->] (b) to node {}(i);
\draw[thick,->] (i) to node {}(c);
\draw[thick,->] (d) to node {}(h);
\draw[thick,->] (b) to node {}(d);
\draw[thick,->] (a) to node {}(e);
\draw[thick,->] (c) to node {}(d);
\draw[thick,->] (e) to node {}(d);
\draw[thick,->] (i) to node {}(d);
\end{tikzpicture} \vspace{3mm}
\end{document}
我浏览了 TikZ/PGF 手册，但找不到答案。关于我做错什么，有什么建议吗？
答案1
我收到以下错误：
! Package PGF Math Error: Unknown function `of' (in 'of a').
See the PGF Math package documentation for explanation.
Type H <return> for immediate help.
...
l.76 [right=of a]
{}; \node[v] (c) [below=of x]{$c$}; \draw[thick,->] (a) to...
?
该语法right=of a是库的扩展/功能positioning。因此，通过加载库可以修复错误。在前言中添加以下行：
\usetikzlibrary{positioning}