change814.cpp

我学习C++ Primer Plus过程中写下的课后作业的编程代码

// 7.修改程序清单8.14,使模板函数返回数组元素的总和,而不是显示数组的内容.
// 程序thing的总和以及所有debt的总和.

#include <iostream>
template <typename T>	//template A
T ShowArray (T arr[], int n);

template <typename T>	//template B
T ShowArray (T * arr[], int n);

struct debts
{
	char name[50];
	double amount;
};

int main(void)
{
	using namespace std;
	int things[6] = {13, 31, 103, 301, 310, 130};
	struct debts mr_E[3] =
	{
		{"Ima Wolfe",2400.0},
		{"Ura Foxe ",1300.0},
		{"Iby Stout",1800.0}
	};
	double* pd[3];
	//set pointers to the amount members of the structures in the arr mr_E
	for (int i = 0; i < 3; i++)
		pd[i] = &mr_E[i].amount;

	cout<<"Listing Mr. E's counts of things:\n";
	//things is an array of int
	ShowArray(things,6);	//uses template A
	cout<<"Listing Mr. E's debts:\n";
	//pd is an array of pointers to double
	ShowArray (pd,3);		//uses template B(more specialized)
	return 0;
}

template <typename T>
T ShowArray (T arr[],int n)
{
	using namespace std;
	T total = 0;
	cout<<"template A\n";
	for (int i = 0; i < n; i++)
		total +=arr[i];
	return total;
}

template <typename T>
T ShowArray (T * arr[], int n)
{
	using namespace std;
	T total = 0;
	cout<< "template B\n";
	for (int i = 0; i < n; i++)
		total += *arr[i];
	return total;
}