error_functions.py 文件源码

def _eval_rewrite_as_Ei(self, nu, z):
        from sympy import exp_polar, unpolarify, exp, factorial
        if nu == 1:
            return -Ei(z*exp_polar(-I*pi)) - I*pi
        elif nu.is_Integer and nu > 1:
            # DLMF, 8.19.7
            x = -unpolarify(z)
            return x**(nu - 1)/factorial(nu - 1)*E1(z).rewrite(Ei) + \
                exp(x)/factorial(nu - 1) * \
                Add(*[factorial(nu - k - 2)*x**k for k in range(nu - 1)])
        else:
            return self