[pstricks] Exiting a parametricplot

[Poul Riis]

How can I exit a parametricplot. The example below works only if I remove
zz 0 lt {exit} if
from the \parametricplot command.

Poul Riis



\documentclass[a4paper,12pt]{article}
\usepackage{inputenc}
\usepackage[T1]{fontenc}
\usepackage[danish]{babel}
\usepackage{amsmath}
\usepackage[usenames,dvipsnames,x11names]{xcolor}
\usepackage{ifthen}
\usepackage{geometry}
\usepackage{multido}
\usepackage{pst-func}
\usepackage{pstricks-add}


\begin{document}
\begin{center}
\psset{unit=2mm}
\begin{pspicture}(-0.5,-0.5)(50,20)
\psaxes[Dx=10,Dy=5,ticksize=-3pt]{->}(0,0)(-0.5,-0.5)(50,20)
\pstVerb{
	/gg 9.82 def
	/v0 20 def
	/c0w 0.2 def
	/costhetac c0w v0 mul gg div 2 div neg def
	/sinthetac costhetac dup mul neg 1 add sqrt def
	/thetac sinthetac costhetac atan def
	/x2 gg c0w div def
	/pi 3.141592 def
}%
\multido{\nn=1+1}{15}{%
\parametricplot[linecolor=Red1,plotpoints=200,linewidth=0.5pt,plotstyle=curve]{0}{60}{/theta
\nn\space 5 mul def	/x1 theta sin v0 mul def /x2 theta cos v0 mul def /tt
t 180 div pi mul c0w div def /zz tt x1 mul tt dup mul gg mul 2 div sub def
zz 0 lt {exit} if t sin x2 mul c0w div  zz}%
}%
\end{pspicture}
\end{center}
\end{document}