有没有大神来解答一下~~

c = 0.767 - 3.36/lambda
beta = PI/sqrt(3.0*lambda)
alpha = beta*lambda
k = log(c) - lambda - log(beta)

forever
{
        u = random()
        x = (alpha - log((1.0 - u)/u))/beta
        n = floor(x + 0.5)
        if (n < 0)
                continue
        v = random()
        y = alpha - beta*x
        lhs = y + log(v/(1.0 + exp(y))^2)
        rhs = k + n*log(lambda) - log(n!)
        if (lhs <= rhs)
                return n
}