Strange behavior using tkz-fct

Question

Lately I've using the tkz-fct package for plotting graphs and I have a document with several graphs but something weird occur when I use \tkzDefPointByFct in some graphs the first graph doesn't have any problem at all

\documentclass{article}
\usepackage{tkz-fct}

\begin{document}
\begin{tikzpicture}
\tkzInit[xmin=-5,xmax=5,ymin=-3,ymax=7]
\tkzGrid[color=gray!40,line width=0.2pt]
\tkzDrawX[color=black,label={$x$},above left=5pt]
\tkzLabelX[color=black]
\tkzDrawY[color=black,label={$y$},below right=5pt]
\tkzLabelY[color=black,orig=false]
\tkzFct[domain=-2:4,color=red,line width=1.2pt]{(x-2)*(x+1)*(x-3)}
\tkzFct[domain=-1:2,color=cyan,line width=1.2pt]{(x-2)*(x+1)*(x-3)}
\tkzFct[domain=3:4,color=cyan,line width=1.2pt]{(x-2)*(x+1)*(x-3)}
\tkzSetUpPoint[size=6,color=cyan,fill=cyan]
\tkzDefPointByFct[draw](-1)
\tkzDefPointByFct[draw](2)
\tkzDefPointByFct[draw](3)
\end{tikzpicture}
\end{document}

With the next code the error FP error: UPN stack is empty!. \tkzDefPointByFct[draw](-2) pops out

\documentclass{article}
\usepackage{tkz-fct}

\begin{document}
\begin{tikzpicture}
\tkzInit[xmin=-6,xmax=4,ymin=-6,ymax=4]
\tkzGrid[color=gray!40,line width=0.2pt]
\tkzDrawX[color=black,label={$x$},above left=5pt]
\tkzLabelX[color=black]
\tkzDrawY[color=black,label={$y$},below right=5pt]
\tkzLabelY[color=black,orig=false]
\tkzFct[domain=-3:2,color=red,line width=1.2pt]{-(2*x-3)*x*(x+2)}
\tkzFct[domain=-2:0,color=cyan,line width=1.2pt]{-(2*x-3)*x*(x+2)}
\tkzFct[domain=1.5:2,color=cyan,line width=1.2pt]{-(2*x-3)*x*(x+2)}
\tkzSetUpPoint[size=6,color=cyan,fill=white]
%Error when activated all these points
%\tkzDefPointByFct[draw](-2) 
%\tkzDefPointByFct[draw](0) 
%\tkzDefPointByFct[draw](1.5)
\end{tikzpicture}
\end{document}

Any ideas of solving this problem? I would like to stick to tkz-fct

Answer 1

Looks like a parsing issue for me ... It compiles without an error after I've applied surrounding brackets () to the equations. Maybe thats required by gnuplot, but I'm not sure.

\documentclass{article}
\usepackage{tkz-fct}

\begin{document}
\begin{tikzpicture}
\tkzInit[xmin=-6,xmax=4,ymin=-6,ymax=4]
\tkzGrid[color=gray!40,line width=0.2pt]
\tkzDrawX[color=black,label={$x$},above left=5pt]
\tkzLabelX[color=black]
\tkzDrawY[color=black,label={$y$},below right=5pt]
\tkzLabelY[color=black,orig=false]
% Addiditional brackets ()
\tkzFct[domain=-3:2,color=red,line width=1.2pt]{(-(2*x-3)*x*(x+2))}
\tkzFct[domain=-2:0,color=cyan,line width=1.2pt]{(-(2*x-3)*x*(x+2))}
\tkzFct[domain=1.5:2,color=cyan,line width=1.2pt]{(-(2*x-3)*x*(x+2))}
\tkzSetUpPoint[size=6,color=cyan,fill=white]
\tkzDefPointByFct[draw](-2)
\tkzDefPointByFct[draw](0)
\tkzDefPointByFct[draw](1.5)
\end{tikzpicture}
\end{document}

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BTW: I kinda love those tikz-packages, because they force me to use my poor French skills ;)