from visual import *

eps = 0.1
maxno = 100
step = 10
dpoint = false
dtangent = true
dnormal = false

L=[]
Laxis=[]
for t in arange(-maxno-eps,maxno+eps, eps):
    L.append(((1-t**2)/(1+t**2), 2*t/(1+t**2)))
    Laxis.append((-4*t/(1+t**2)**2, 2*(1-t**2)/(1+t**2)**2))

curve(pos = L, radius = 0.05, color=color.red)
if dpoint: points(pos = L, radius = 0.1, color=color.white)
for i in arange(len(L)):
    if i % step == 0:
         if dtangent: arrow(pos = L[i], axis = Laxis[i], shaftwidth=0.01, color = color.blue)
         if dnormal: arrow(pos = L[i], axis = (Laxis[i][1], -Laxis[i][0]), shaftwidth=0.01, color=color.green)