验证函数是向量空间

class Polynomial(Vector):
    def __init__(self, *coefficients):
        self.coefficients = coefficients
    def __call__(self,x):
        return sum(coefficient * x ** power for (power,coefficient) in enumerate(self.coefficients))
    def add(self,p):
        return Polynomial([a + b for a,b in zip(self.coefficients, p.coefficients)])
    def scale(self,scalar):
        return Polynomial([scalar * a for a in self.coefficients])
    def _repr_latex_(self):
        monomials = [repr(coefficient) if power == 0 
                               else "x ^ {%d}" % power if coefficient == 1
                               else "%s x ^ {%d}" % (coefficient,power) 
                               for (power,coefficient) in enumerate(self.coefficients) 
                               if coefficient != 0]
        return "$ %s $" % (" + ".join(monomials))
    @classmethod
    def zero(cls):
        return Polynomial(0)

def random_function():
    degree = randint(0,5)
    p = Polynomial(*[uniform(-10,10) for _ in range(0,degree)])
    return Function(lambda x: p(x))

for i in range(0,100):
    a,b = random_scalar(), random_scalar()
    u,v,w = random_function(), random_function(), random_function()
    test(Function.zero(), approx_equal_function, a,b,u,v,w)