def fill_array(x,x_val):
  """
  fill_array(x,x_val)

  If x_val[i] != None then x[i] == x_val[i].
  """
  constraints = []
  for i in range(len(x)):
    if x_val[i] != None:
      constraints += [x[i] == x_val[i]]

  return constraints