from __future__ import division
from visual import *

## INITIAL VALUE OF B
B0 = vector(0,0.2,0)

## THIS CODE DRAWS A FLOOR AND DISPLAYS THE MAGNETIC FIELD *************
xmax = .6
dx = .1
yg = -.1
for x in arange(-xmax, xmax+dx, dx):
    curve(pos=[(x,yg,-xmax),(x,yg,xmax)], color=(.7,.7,.7))
for z in arange(-xmax, xmax+dx, dx):
    curve(pos=[(-xmax,yg,z),(xmax,yg,z)],color=(.7,.7,.7))
bscale = 1
for x in arange(-xmax, xmax+dx, 2*dx):
    for z in arange(-xmax, xmax+dx, 2*dx):
        arrow(pos=(x,yg,z), axis=B0*bscale, color=(0,.8,.8))

## YOUR PROGRAM BEGINS HERE ##*******************************************

deltat = 1e-11
t = 0.
while 1: ## Implement steps 1-3 after making the proton move in a straight line (step 4).
    ## 1) Add code to calculate the magnetic force on moving proton.
    ##   The function cross(a,b) calculates the cross product axb.


    ## 2) Calculate the new momentum of the proton (see handout).


    ## 3) Calculate the new velocity of the proton (p/m).


    ## 4) Update the position of the proton (initially, it moved in a straight line).