# possible stops: 4,6,8
# f: f(x). g: f'(x).

flist=f '(x),-f '(x),f '(-x),-f '(-x),	f '(x+1),f '(x-1),f '(x)+1,f '(x)-1
xlist=t,t,-t,-t,			t-1,t+1,t,t
ylist=g,-g,g,-g,			g,g,g+1,g-1

