//
// why the existence of no parallel is a contraction
clf

plot([-2,2],[-1,-1],'k-');
plot(0,1,'ko');
plot(0,1.5,'wo');
xstring(0,1,'A');
e=gce(); e.font_size=4;
//xstring(0,-1,'B');
//e=gce(); e.font_size=4;
a=gca();
a.isoview="on";
a.axes_visible=["off","off","off"];
a.box="off";
xs2pdf(0,'p0.pdf');
sleep(1000);

plot([0,0],[-1.5,1.5],'k-');
d=0.3;
plot([0,d],[-1+d,-1+d],'r-');
plot([d,d],[-1,-1+d],'r-');
xstring(0,-1,'B');
e=gce(); e.font_size=4;
a=gca();
a.isoview="on";
a.axes_visible=["off","off","off"];
a.box="off";
xs2pdf(0,'p1.pdf');
sleep(1000);

plot([-0,2],[1,1],'k-');
plot([0,d],[1-d,1-d],'r-');
plot([d,d],[1,1-d],'r-');
a=gca();
a.isoview="on";
a.axes_visible=["off","off","off"];
a.box="off";
xs2pdf(0,'p2.pdf');
sleep(1000);

clf
plot([0,0],[-1.5,1.5],'k-');
plot([-0,2],[-1,-1],'k-');
plot([-0,2],[1,1],'k-');
d=0.3;
plot([0,d],[-1+d,-1+d],'r-');
plot([d,d],[-1,-1+d],'r-');
plot([0,d],[1-d,1-d],'r-');
plot([d,d],[1,1-d],'r-');
xstring(0,1,'A');
e=gce(); e.font_size=4;
xstring(0,-1,'B');
e=gce(); e.font_size=4;
a=gca();
a.isoview="on";
a.axes_visible=["off","off","off"];
a.box="off";
xs2pdf(0,'p3.pdf');
sleep(1000);

x = 2:0.1:11;
plot(x,1-(x-2)/8,'k:')
plot(x,-1+(x-2)/8,'k:')
xstring(10,0,"X");
e=gce(); e.font_size=4;
a=gca();
a.isoview="on";
a.data_bounds=[-3,11,-3,3];
a.axes_visible=["off","off","off"];
a.box="off";
xs2pdf(0,'p4.pdf');
sleep(1000);

plot(-x+2,1-(x-2)/8,'k:')
plot(-x+2,-1+(x-2)/8,'k:')
xstring(-8,0,"Y");
e=gce(); e.font_size=4;

a=gca();
a.data_bounds=[-11,11,-3,3];
a.isoview="on";
a.axes_visible=["off","off","off"];
a.box="off";

xs2pdf(0,'p5.pdf');

plot([0,-d],[-1+d,-1+d],'r-');
plot([-d,-d],[-1,-1+d],'r-');
plot([0,-d],[1-d,1-d],'r-');
plot([-d,-d],[1,1-d],'r-');

a=gca();
a.data_bounds=[-11,11,-3,3];
a.isoview="on";
a.axes_visible=["off","off","off"];
a.box="off";

xs2pdf(0,'p6.pdf');
