def collision(ent1, ent2):
# Edge cases
if ent1 is ent2:
return True, Pair(0.0, 0.0)
# If the entities are in the same position,
if math.isclose(ent1.x, ent2.x) and math.isclose(ent1.y, ent2.y):
# if they have the same velocity
if math.isclose(ent1.vx, ent2.vx) and math.isclose(ent1.vy, ent2.vy):
# find their normalised common velocity
ux, uy = ent1.vx + ent2.vx, ent1.vy + ent2.vy
l = math.sqrt(ux**2 + uy**2)
ux, uy = ux / l, uy / l
# and return a correction vector perpendicular to that,
# with magnitude of the sum of their radii.
s = ent1.r + ent2.r
return True, Pair(-uy * s, ux * s)
# If they don't have the same velocity, same as above
# but with their relative velocity.
ux, uy = ent1.vx - ent2.vx, ent1.vy - ent2.vy
l = math.sqrt(ux**2 + uy**2)
ux, uy = ux / l, uy / l
s = ent1.r + ent2.r
return True, Pair(-uy * s, ux * s)
# Main case
flag = (ent1.x - ent2.x)**2 + (ent1.y - ent2.y)**2 <= (ent1.r + ent2.r)**2
if flag:
dx = ent2.x - ent1.x
dy = ent2.y - ent1.y
s = math.sqrt(dx**2 + dy**2)
factor = (ent1.r + ent2.r) / s - 1
return True, Pair(dx * factor, dy * factor)
else:
return False, None
def test_find_empty():
with pytest.raises(ValueError):
bst = BST()
item = bst.find(Pair('A'))
