Problem getting morphed binary stars code to work

[rbarve]

This program below is an attempt to implement the one here : http://www.glowscript.org/#/user/GlowScriptDemos/folder/Examples/program/BinaryStar-VPython/edit
but it doesnt work.. This was on Chrome beta 42.0 on Ubuntu 14.04
Notes:
(a) I replaced the while True with the recursive version as in Pyschool's bounce
(a) There seem to be some associative rule issues : the expression
F = G * giant.mass * dwarf.mass * norm(r) / mag2(r)
doesnt work even with r.norm() and r.mag2() so that I had to use :
coeff = G * giant.mass * dwarf.mass/r.mag2()
F = r.norm() * coeff
to make it work..
(b) Initially I had the make_trail params to the spheres left as in the original vPython. But the program seemed to be executing with canvas/scene completely blank. Since I recall reading somewhere that make_trail had issues in brython-glow, I removed the make_trail params but still the canvas/scene is blank..

from glow import *

glow('pydiv')
scene = canvas()

scene.forward = vec(0,-.3,-1).to_glowscript()

G = 6.7e-11

giant = sphere(pos=vec(-1e11,0,0), radius=2e10, color=color.red)
giant.mass = 2e30
giant.p = vec(0, 0, -1e4) * giant.mass

dwarf = sphere(pos=vec(1.5e11,0,0), radius=1e10, color=color.yellow)
dwarf.mass = 1e30
dwarf.p = vec(0,0,0)-giant.p
r = dwarf.pos - giant.pos
coeff = G * giant.mass * dwarf.mass/r.mag2()
q = r.norm()*coeff
print("q",q)

dt = 1e5
def move():
r = dwarf.pos - giant.pos
#F = G * giant.mass * dwarf.mass * norm(r) / mag2(r)
coeff = G * giant.mass * dwarf.mass/r.mag2()
F = r.norm() * coeff
giant.p = giant.p + F_dt
dwarf.p = dwarf.p - F_dt
giant.pos = giant.pos + (giant.p/giant.mass) * dt
dwarf.pos = dwarf.pos + (dwarf.p/dwarf.mass) * dt

rate(200,move)

print("start exec")
move()

[rbarve]

Update -- when I replaced the radius arg with a size vector arg for the spheres the code started working
However the associative rule problem of mult and div above remains. And the attach trail issue also remains .. below code works as expected without the trails

from glow import *

glow('pydiv')
scene = canvas()

scene.forward = vec(0,-.3,-1).to_glowscript()

G = 6.7e-11

giant = sphere(pos=vec(-1e11,0,0), size=vec(2e10,2e10,2e10), color=color.red,make_trail=True, trail_type='points', interval=10, retain=50)
giant.mass = 2e30
giant.p = vec(0, 0, -1e4) * giant.mass

dwarf = sphere(pos=vec(1.5e11,0,0), size=vec(1e10,1e10,1e10), color=color.yellow,make_trail=True,trail_type='points', interval=10, retain=40)
dwarf.mass = 1e30
dwarf.p = vec(0,0,0)-giant.p
r = dwarf.pos - giant.pos
coeff = G * giant.mass * dwarf.mass/r.mag2()
q = r.norm()*coeff
print("q",q)

dt = 1e5
def move():
r = dwarf.pos - giant.pos
#F = G * giant.mass * dwarf.mass * norm(r) / mag2(r)
coeff = G * giant.mass * dwarf.mass/r.mag2()
F = r.norm() * coeff
giant.p = giant.p + F_dt
dwarf.p = dwarf.p - F_dt
giant.pos = giant.pos + (giant.p/giant.mass) * dt
dwarf.pos = dwarf.pos + (dwarf.p/dwarf.mass) * dt
rate(200,move)

move()

[rbarve]

Actually one of the issues above -- the (a) issue -- is because you cant do Number*vec():

from glow import *
glow('pydiv')

a=vec(1,2,1)
b=a_2
print('b',b)
c=2_a
print('c',c)

[ghost]

Thanks for reporting this issue, and figuring out most of the issues. I'll look into adding/fixing the issue dealing with multiplying a vector by a number.