梯形法求定积分（二）--设计一个函数模板，独立的非成员函

/*设计梯形法求定积分的函数模板，这个方法比之前的那个设计求积分的类要思路简单得多，

而且我个人认为这么想更顺*/

#include<iostream>

#include<cmath>

using namespace std;

class Mysin{

public:

double fun(double x)

{

return (sin(x));

}

};

class F1{

public:

double fun(double x)

{

return (1+x+2*x*x);

}

};

class F2{

public:

double fun(double x)

{

return (1+x+2*x*x+3*x*x*x);

}

};

template<class T>

double JiFenHanShu(T cf,double a,double b,int n)

{

double h,result=0;

h=(b-a)/n;

result += (cf.fun(a)+cf.fun(b))/2;

for(int i=1;i<n;i++)

result += cf.fun(a+i*h);

result *= h;

return result;

}

void main()

{

Mysin f1;

F1 f2;

F2 f3;

double jieguo1;

double jieguo2;

double jieguo3;

jieguo1=JiFenHanShu(f1,0.0,3.0,1000);

cout<<"函数f1的定积分值是:"<<jieguo1<<endl;

jieguo2=JiFenHanShu(f2,0.0,3.0,1000);

cout<<"函数f2的定积分值是:"<<jieguo2<<endl;

}