在 TikZ 中创建循环箭头

Question

我试图创建一个箭头，从单词底部向外延伸，然后绕到同一个单词的顶部。重点是说明“Operations”的输出也成为“Operations”的输入。

我最初的尝试只是使用edge[out = -90, in = 90]，但这并不能使箭头围绕单词循环。

\documentclass{article}
\usepackage{tikz}

\begin{document}
\begin{tikzpicture}
    \node at (0,0) (Operations) {Operations};
    \draw [->] (Operations) edge[out = -90, in = 90] (Operations);
\end{tikzpicture}

\end{document}

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编辑

在我的实际示例中，我有一个箭头从上方的节点指向“操作”，还有一个箭头从“操作”指向下方的节点。循环箭头的起点和终点最好与这两个现有箭头对齐。

\documentclass{article}
\usepackage{tikz}

\begin{document}
\begin{tikzpicture}
    \node at (0,3) (Input) {Input};
    \node at (0,1.5) (Operations) {Operations};
    \node at (0,0) (Output) {Output};
    \draw [->] (Input) -- (Operations);
    \draw [->] (Operations.center) arc (-180:180:1);
    \draw [->] (Operations) -- (Output);
\end{tikzpicture}

\end{document}

Answer 1

这里有一个非常棘手的解决方案，即添加第三个节点\node at (1,0) (here) {};并修改箭头的大小looseness。

\documentclass{article}
\usepackage{tikz}
\begin{document}
\begin{tikzpicture}
    \node at (0,0) (Operations) {Operations};
    \node at (1,0) (here) {};
    \draw [->] (Operations) to[out=-80, in=-90,looseness=2] (here)    to[out=90,in=80,looseness=2] (Operations);
\end{tikzpicture}

\end{document}

Answer 2

正如我在评论中所说，精确的数字

\documentclass{article}
\usepackage{tikz}

\begin{document}
\begin{tikzpicture}
    \node at (0,0) (Operations) {Operations};
    \draw [->] (Operations.south)arc(-160:160:1);
\end{tikzpicture}

\end{document}

---

---

另一种方法

\draw[->,shorten <=5pt,shorten >=5pt](Operations.center)arc(-180:180:1);

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第三种方法

\documentclass{article}
\usepackage{tikz}

\begin{document}
\begin{tikzpicture}
    \node at (0,3) (Input) {Input};
    \node at (0,1.5) (Operations) {Operations};
    \node at (0,0) (Output) {Output};
    \draw [->] (Input) -- (Operations);
    \draw [->] (Operations) -- (Output);
    \draw[->](Operations.south)arc(-180:0:1)coordinate(X)
             (Operations.north)+(2,0)--(X)
             (Operations.north)+(2,0)arc(0:180:1);
\end{tikzpicture}

\end{document}