使用 TikZ 绘制对偶字符串图

Question

我想用 TikZ 重现以下图表

如果能将它们旋转 90 度（使其类似于杯子和帽子的符号）就好了。我搜索了如何创建拱门，但似乎不符合我想要的结果：有没有更简单的解决方案？

Answer 1

那样的东西适合你吗？

\documentclass[tikz,border=3.14mm]{standalone}
\usetikzlibrary[decorations.markings]

\begin{document}
    \begin{tikzpicture}[arr/.style={
            postaction={decorate},          
            decoration={
            markings,
            mark=at position #1 with {\arrow{>}}}}]
    
        \draw[arr=0.6] (0,0) -- (0,1) node[pos=0.6,right]{A};
        \draw (0,1) to[out=90,in=90,looseness=2] (1,1);
        \draw[arr=0.5] (1,1) -- (1,0)node[pos=0.4,right]{A};
        \draw (1,0) to[out=-90,in=-90,looseness=2] (2,0);   
        \draw[arr=0.6] (2,0) -- (2,1)node[pos=0.6,right]{A};
    \end{tikzpicture}
\end{document}

Answer 2

你也可以使用arcs。对于一般形状，类似

\draw (0,0) -- (0,1)  arc[start angle=180, delta angle=-180, radius=0.5]
            -- (1,0)  arc[start angle=180, delta angle=180, radius=0.5]
            -- (2,1);

由于垂直线相距 1，因此圆弧的半径为 0.5。 定义start angle了 所属圆的“锚点” arc 。对于这两种情况，arc应该从圆的最左点开始，start angle=180。由于第一条圆弧从 180 度逆时针旋转到零度，因此我设置delta angle=-180。第二条圆弧顺时针旋转，因此delta angle=180。

各种例子，其中我采用了arr标记的风格 SebGlav 的回答，因此，这值得称赞。

\documentclass[tikz,border=3.14mm]{standalone}
\usetikzlibrary{decorations.markings}
\tikzset{
  arr/.style={
            postaction={decorate},          
            decoration={
            markings,
            mark=at position #1 with {\arrow{>}}}}
}
\begin{document}
% just simple shape
\begin{tikzpicture}
\draw (0,0) -- (0,1)  arc[start angle=180, delta angle=-180, radius=0.5]
            -- (1,0) arc[start angle=180, delta angle=180, radius=0.5]
            -- (2,1);
\end{tikzpicture}

% same shape with arrows
% arrow positions found by trial and error
\begin{tikzpicture}[
  arr/.style={
              postaction={decorate},          
              decoration={
                 markings,
                 mark=at position 0.1 with {\arrow{>}},
                 mark=at position 0.5 with {\arrow{>}},
                 mark=at position 0.925 with {\arrow{>}}
            }
   }
]

\draw [arr] (0,0) -- (0,1)  arc[start angle=180, delta angle=-180, radius=0.5]
                  -- (1,0)  arc[start angle=180, delta angle=180, radius=0.5]
                  -- (2,1);
\end{tikzpicture}

% separate paths
\begin{tikzpicture}
% first the three straight lines
% saving some coordinates for use later
\draw [arr=0.5] (0,0) -- node[left] {$A$} (0,1) coordinate (m1);
\draw [arr=0.5] (1,1) -- node[left] {$A$} (1,0) coordinate (m2);
\draw [arr=0.5] (2,0) -- node[left] {$A$} (2,1);

% then the two arcs
\draw (m1) arc[start angle=180, delta angle=-180, radius=0.5]
      (m2) arc[start angle=180, delta angle=180, radius=0.5];
\end{tikzpicture}


% single draw, but with edge (which actually makes separate paths)
% because of edge, coordinates have to be repeated
\begin{tikzpicture}   
     \draw (0,0)   edge[arr=0.5] node[left] {$A$} (0,1)
           (0,1) arc[start angle=180, delta angle=-180, radius=0.5]
                   edge[arr=0.5] node[left] {$A$} (1,0)
           (1,0) arc[start angle=180, delta angle=180, radius=0.5]
                   edge[arr=0.5] node[left] {$A$} (2,1);

\end{tikzpicture}
\end{document}