使用BBsolve时，可以使用printres参数来打印结果。例如，对于以下的非线性方程组：

from numpy import *
from enthought.traits.api import *
from enthought.traits.ui.api import *
from enthought.tvtk.pyface.ui.api import Scene

from bbdemos import BjerkDemo
from bbdemos import double_pendulum

class DoublePendulum(BjerkDemo):
    theta1, theta2 = double_pendulum.init()
    L1=1.0
    L2=2.0
    m1 = 1.0
    m2 = 2.0
    g = 9.81

    def __init__(self,show_gui=True,dt=0.001):
        BjerkDemo.__init__(self,show_gui=show_gui,dt=dt)
    def f1(self,u,t):
        return array([
                u[2],
                u[3],
                (-self.m1*self.L1*sin(u[0])*u[2]**2 +
                 (self.m1 + self.m2)*self.g*sin(u[0]) -
                 self.m2*self.L2*sin(u[0]-u[1])*u[3]**2)/
                 (self.m1 + self.m2*self.sin(u[0]-u[1])**2),
                ( (self.m1 + self.m2)*self.L1*sin(u[0])*u[2]**2 +
                  self.m2*self.L2*sin(u[0]-u[1])*u[3]**2 +
                  (self.m1+self.m2)*self.g*sin(u[0]+u[1]))/
                 (self.m1 + self.m2*self.sin(u[0]-u[1])**2)
            ])
    def dfdu(self,u,t):
        alpha = self.m2*self.L1*self.L2*cos(u[0]-u[1])
        beta = self.m2*self.sin(u[0]-u[1])
        gamma = self.m1*self.L1 + self.m2*self.L2
        delta = self.m2*self.g*cos(u[1])

        df1du1 = array([0, 0, 1, 0])
        df1du2 = array([0, 0, 0, 1])
        df1du3 = array([
                    -delta*(2*alpha*beta*gamma + (2*alpha*beta)**2)/((gamma**2)*(beta**2) + alpha**2)**2,
                    0,
                    -gamma*(delta*beta**2 + alpha*gamma*self.g)/(gamma**2*beta**2 + alpha**2),
                    delta*beta