运行以下示例代码时，出现 TeX 容量超出错误（来自这个问题的答案：
\documentclass{article}
\usepackage{lmodern}
\usepackage[T1]{fontenc}
\usepackage{tikz}
\usetikzlibrary{calc, hobby}
\tikzset{tangent/.style = \tikzset{
tangent/.style = {
in angle={(180+#1)},
Hobby finish,
designated Hobby path=next,
out angle=#1
}
}}
\begin{document}
\begin{figure}[htbp]
\centering
\begin{tikzpicture}
\coordinate (y) at (0,3);
\coordinate (x) at (5,0);
\coordinate (sp0) at (1.5, 0);
\coordinate (ep0) at (3.5, 2);
\coordinate (csp0) at (2.5, 1);
\coordinate (cep0) at (2.75, 0);
\coordinate (sp1) at (ep0);
\coordinate (ep1) at (4.5, 3);
\coordinate (csp1) at (4.25, 4);
\coordinate (cep1) at (4.25, 2);
\coordinate (sp2) at (sp0);
\coordinate (ep2) at (0, -1);
\coordinate (csp2) at (0.5, -1);
\coordinate (cep2) at (0.5, -1);
\draw[<->] (y) node[left] {$f(x)$} -- (0,0) -- (x) node[below] {$x$};
% Using \pgfmathanglebetweenpoints to calculate the angle for tangent
% tangent takes a degree unit angle
\pgfmathanglebetweenpoints{\pgfpointanchor{cep0}{center}}{\pgfpointanchor{ep0}{center}}
\let\angle=\pgfmathresult
\draw (ep2) to [curve through ={(sp0) .. ([tangent=\angle]ep0)}] (ep1) ;
\draw[dashed] (cep0) -- (csp1);
\draw[dotted] let \p1 = (ep0) in (ep0) -- (0, \y1);
\draw[dotted] let \p1 = (ep0) in (ep0)-- (\x1, 0);
\draw let \p1 = (ep0) in (\x1,1pt) -- (\x1,-3pt) node[anchor=north] {$x_0$};
\draw let \p1 = (cep0) in (\x1,1pt) -- (\x1,-3pt) node[anchor=north] {$x_1$};
\draw let \p1 = (ep0) in (1pt, \y1) -- (-3pt, \y1) node [anchor=east] {$f(x_0)$};
\end{tikzpicture}
\caption{Newton's method in action: diagram drawn using the \texttt{hobby} package.}
\label{fig:newton_method_2}
\end{figure}
\end{document}
日志中的完整错误如下：
! TeX capacity exceeded, sorry [parameter stack size=10000].
\pgfkeys@@qset #1#2#3->
\def \pgfkeysdefaultpath {#2/}\pgfkeys@parse #3,\pgfk...
l.85 ...h ={(sp0) .. ([tangent=\angle]ep0)}] (ep1)
;
If you really absolutely need more capacity,
you can ask a wizard to enlarge me.
搜索此错误后，我发现解决方案有时非常晦涩难懂……所以我完全不确定问题出在哪里。我能按照错误消息的建议简单地“增加容量”吗？
答案1
您正在尝试将样式设置为该样式定义的一部分。因此 TiKZ 陷入困境，因为设置是恶性递归的。
\documentclass{article}
\usepackage{lmodern}
\usepackage[T1]{fontenc}
\usepackage{tikz}
\usetikzlibrary{calc, hobby}
\tikzset{
tangent/.style = {
in angle={(180+#1)},
Hobby finish,
designated Hobby path=next,
out angle=#1
}
}
\begin{document}
\begin{figure}[htbp]
\centering
\begin{tikzpicture}
\coordinate (y) at (0,3);
\coordinate (x) at (5,0);
\coordinate (sp0) at (1.5,0);
\coordinate (ep0) at (3.5,2);
\coordinate (csp0) at (2.5,1);
\coordinate (cep0) at (2.75,0);
\coordinate (sp1) at (ep0);
\coordinate (ep1) at (4.5,3);
\coordinate (csp1) at (4.25,4);
\coordinate (cep1) at (4.25,2);
\coordinate (sp2) at (sp0);
\coordinate (ep2) at (0,-1);
\coordinate (csp2) at (0.5,-1);
\coordinate (cep2) at (0.5,-1);
\draw[<->] (y) node[left] {$f(x)$} -- (0,0) -- (x) node[below] {$x$};
% Using \pgfmathanglebetweenpoints to calculate the angle for tangent
% tangent takes a degree unit angle
\pgfmathanglebetweenpoints{\pgfpointanchor{cep0}{center}}{\pgfpointanchor{ep0}{center}}
\let\angle=\pgfmathresult
\draw (ep2) to [curve through ={(sp0) .. ([tangent=\angle]ep0)}] (ep1) ;
\draw[dashed] (cep0) -- (csp1);
\draw[dotted] let \p1 = (ep0) in (ep0) -- (0,\y1);
\draw[dotted] let \p1 = (ep0) in (ep0)-- (\x1,0);
\draw let \p1 = (ep0) in (\x1,1pt) -- (\x1,-3pt) node[anchor=north] {$x_0$};
\draw let \p1 = (cep0) in (\x1,1pt) -- (\x1,-3pt) node[anchor=north] {$x_1$};
\draw let \p1 = (ep0) in (1pt,\y1) -- (-3pt,\y1) node [anchor=east] {$f(x_0)$};
\end{tikzpicture}
\caption{Newton's method in action: diagram drawn using the \texttt{hobby} package.}
\label{fig:newton_method_2}
\end{figure}
\end{document}
我不知道它们是否在这里造成了问题，但请注意，TiKZ/PGF 也对空格敏感，因此在使用时要注意一致性。
