为什么 \pgfmathresult 似乎给出两个不同的答案？

Question

我正在尝试使用\foreach循环来制作一些由线连接的交替圆圈链。我曾经\pgfmathparse让小蓝色圆圈在大橙色圆圈的每一侧摆动。出于某种原因，pgfmathresult在定位小蓝色圆圈时有效，但对于连接圆圈的线似乎不起作用。

\documentclass[tikz]{standalone}

\usepackage{tikz}

\begin{document}

    \begin{tikzpicture}
        \foreach \i in {-3,...,3} {
            \pgfmathparse{pow(-1,\i+3)*0.5};
            \draw[fill=blue!30!white] (\i+0.5,\pgfmathresult) circle (0.1cm);
            \draw(\i,0) -- (\i+0.5,\pgfmathresult) -- (\i+1,0);
            \draw[fill=orange!60!white] (\i,0) circle (0.3cm);
        }
    \end{tikzpicture}

\end{document}

该输出应显示连接到相邻的小圆和大圆的实线。

Answer 1

    \documentclass[tikz]{standalone}

\usepackage{tikz}

\begin{document}
    
    \begin{tikzpicture}
        \foreach \i [evaluate=\i as \in using {pow(-1,\i+3)*0.5}]  in {-3,...,3} {
%           \pgfmathtruncatemacro{\in}{pow(-1,\i+3)*0.5};
            \draw(\i,0) -- (\i+0.5,\in) -- (\i+1,0);
            \draw[fill=blue!30!white] (\i+0.5,\in) circle (0.1cm);
%           \draw(\i,0) -- (\i+0.5,\in) -- (\i+1,0);
            \draw[fill=orange!60!white] (\i,0) circle (0.3cm);
        }
    \end{tikzpicture}
    
\end{document}

Answer 2

节点也一样：

\documentclass[tikz,border=3.14mm]{standalone}


\begin{document}
    
    \tikzset{
        orangenode/.style={draw,circle,inner sep=0pt,minimum width=6mm,fill=orange!60},
        bluenode/.style={draw,circle,inner sep=0pt,minimum width=2mm,fill=blue!30}
        }
        
    \begin{tikzpicture}
        \foreach \i in {-3,...,3} {
            \pgfmathsetmacro\j{pow(-1,\i+3)*0.5};
            \node[orangenode] (O-\i) at (\i,0) {};
            \node[bluenode] (B-\i) at (\i+0.5,\j) {};
        }
        \foreach \i in {-3,...,3} {
            \draw (O-\i) -- (B-\i);
            \pgfmathtruncatemacro\j{\i+1};
            \ifnum \j<4 \draw (B-\i) -- (O-\j); \fi
            }
            
    \end{tikzpicture}

\end{document}