使用 \foreach 的评估选项在 TikZ 中显示整数而不是浮点数

Question

\documentclass{article}
\usepackage{tikz}
\begin{document}

 \begin{tikzpicture}
      \draw[->] (-2,0) -- (2,0) node[right] {$x$};  
      \draw[->] (0,-2) -- (0,2) node[above] {$y$};
      \foreach \x in {-3,...,3} 
               \draw (\x/2,1pt) -- (\x/2,-2pt);
      \foreach \y in {-3,...,3} 
               \draw (1pt,\y/2) -- (-2pt,\y/2);
      \draw[thick,db] (0,0) circle (1.5cm);
      \foreach \x [evaluate=\x as \r using \x/1.5] in {-1.5, 1.5} 
               \draw (\x cm,1pt) -- (\x cm,-1pt) 
                      node[anchor=north, fill=white] {\tiny $\r$};

\end{tikzpicture}%
\end{document} 

结果是

我希望它显示 -1 和 1，而不是 -1.0 或 1.0。该怎么做？

Answer 1

int(...)为了获得整数结果，请在计算\r节点文本时使用 TikZ 函数：

\documentclass{article}
\usepackage{tikz}
\begin{document}

 \begin{tikzpicture}
      \draw[->] (-2,0) -- (2,0) node[right] {$x$};  
      \draw[->] (0,-2) -- (0,2) node[above] {$y$};
      \foreach \x in {-3,...,3} 
               \draw (\x/2,1pt) -- (\x/2,-2pt);
      \foreach \y in {-3,...,3} 
               \draw (1pt,\y/2) -- (-2pt,\y/2);
      \draw[thick,blue] (0,0) circle (1.5cm);
      \foreach \x [evaluate=\x as \r using int(\x/1.5)] in {-1.5, 1.5} 
               \draw (\x cm,1pt) -- (\x cm,-1pt) 
                      node[anchor=north, fill=white] {\tiny $\r$};

\end{tikzpicture}%
\end{document} 

Answer 2

只是为了完整性。在这种情况下，不需要评估任何东西，因为坐标会自动解析，所以你可以简单地做

\foreach \X in {-1, 1} 
               \draw (\X*1.5cm,1pt) -- (\X*1.5cm,-1pt) 
                      node[anchor=north, fill=white,font=\tiny] {$\X$};

请注意，\x如果您打算使用，这可能不是一个好的循环变量calc。

\documentclass{article}
\usepackage{tikz}
\begin{document}

 \begin{tikzpicture}
      \draw[->] (-2,0) -- (2,0) node[right] {$x$};  
      \draw[->] (0,-2) -- (0,2) node[above] {$y$};
      \foreach \X in {-3,...,3} 
               \draw (\X/2,1pt) -- (\X/2,-2pt);
      \foreach \y in {-3,...,3} 
               \draw (1pt,\y/2) -- (-2pt,\y/2);
      \draw[thick,blue!80!black] (0,0) circle (1.5cm);
      \foreach \X in {-1, 1} 
               \draw (\X*1.5cm,1pt) -- (\X*1.5cm,-1pt) 
                      node[anchor=north, fill=white,font=\tiny] {$\X$};

\end{tikzpicture}%
\end{document}