定积分（任意函数求积分）

 1 #define eps 1e-8

 2 

 3 double fun(double x) {

 4     /*函数部分*/

 5 }

 6 

 7 double Definite_Integral(double a, double b) {

 8     double p = eps + 1.0;

 9     double t, h = b - a, t1 = (fun(a) + fun(b)) * h / 2;

10     while(p >= eps) {

11         double s = 0;

12         for(double k = a + h / 2; k <= b; k += h)s += fun(k);

13         t = t1 / 2 + h * s / 2;

14         p = fabs(t - t1);

15         t1 = t;

16         h /= 2;

17     }

18     return t;

19 }