! \pgfmathrnd@@ 的参数有一个额外的 }

Question

以下代码出现此错误：

! Argument of \pgfmathrnd@@ has an extra }.
<inserted text> 
                \par 
l.12    }

? 
! Emergency stop.
<inserted text> 
                \par 
l.12    }

!  ==> Fatal error occurred, no output PDF file produced!
Transcript written on bob.log.

Done.

怎么了 ？

\documentclass[tikz]{standalone}
\usetikzlibrary{patterns}

\pgfdeclarepatternformonly{Rnd}
{\pgfpointorigin}{\pgfpoint{.5cm}{.5cm}}
{\pgfpoint{1cm}{1cm}}
{
    \pgfpathcircle{%
        %\pgfpoint{.25cm}{.25cm}}{.4pt}
        \pgfpoint{\pgfmathrnd*.25cm}{\pgfmathrnd*.25cm}}{.4pt}
    \pgfusepath{fill}
}

\begin{document}
\begin{tikzpicture}

\draw[pattern=Rnd] (0,0) rectangle (5,5) ;
\end{tikzpicture}

\end{document}

Answer 1

在这种情况下，无法使用宏\pgfmathrnd，\pgfmathrand否则\pgfmathrandom结果将不是适合解析的形式。正确的方法是直接使用函数rnd，rand或random：

\pgfpoint{rnd*.25cm}{rnd*.25cm}}{.4pt}