程序清单7.6
#include<iostream>
using namespace std; const int Size = ;
int sum_arr(int arr[], int n);//函数声明
void main()
{
int cookies[Size] = { ,,,,,,, };
cout << cookies << " =array address," << sizeof cookies << " =sizeof cookies" << endl;
int sum = sum_arr(cookies, Size);
cout << "Total cookies eaten: " << sum << endl;
sum = sum_arr(cookies, );
cout << "First three eaters ate " << sum << endl;
sum = sum_arr(cookies+,);
cout << "Last four eaters ate " << sum << endl; system("pause");
} int sum_arr(int arr[], int n)//输出地址，大小，计算和
{
int total = ;
cout << arr << " =arr," << sizeof(arr) << " =sizeof(arr)" << endl;
for (int i = ; i <n; i++)
total += arr[i];
return total;
}
指针和const
const的位置不同，指针可以进行的操作也不同
month数组被const修饰了，所以如果要使用sum函数的话，需要修改第四行代码
int sum(const int arr[],int n)
函数和二维数组
先修知识：指针数组和数组指针
#include <iostream>
using namespace std; int main()
{
int c[] = { ,,, };
int *a[]; //指针数组
int(*b)[]; //数组指针
b = &c;
for (int i = ; i<; i++)//将数组c中元素赋给数组a
{
a[i] = &c[i];
}
cout << *a[] << endl; //输出2就对
cout << (*b)[] << endl; //输出3就对
return ;
}
OK，进入正题，函数与二维数组
#include<iostream>
using namespace std; //数组表示法
int sum(int arr[][], int n)
{
int total = ;
for (int r = ; r < n; r++)
{
for (int c = ; c < ; c++)
{
cout << arr[r][c] << "\t";
total += arr[r][c];
}
cout << endl;
}
return total;
} //指针表示法
int sum2(int (*arr)[],int n)//数组指针：指向数组的指针
{
int total = ;
for (int r = ; r < n; r++)
{
for (int c = ; c < ; c++)
{
cout << *(*(arr+r)+c)<< "\t";//arr是一个指向数组（4个int整数）的指针，*（arr+r）=arr[r]表示指向第（r+1）个数组
total += *(*(arr + r) + c);
}
cout << endl;
}
return total;
} void main()
{
int data[][] = { {,,,},{,,,},{,,,} };
int s = sum(data, );
cout << s << endl;
getchar();
}
程序清单7.11
#include<iostream>
using namespace std; const int Rate = ;
struct time {
int hour;
int mins;
}; time sum(time a, time b) {
time total;
total.hour = a.hour + b.hour + (a.mins + b.mins) / Rate;
total.mins = (a.mins + b.mins) % ;
return total;
}
void show(time t) {
cout << t.hour << " hours," << t.mins << " minutes." << endl;
} void main()
{
time d1 = { , };
time d2 = { , };
time trip = sum(d1, d2);
cout << "Two_day total:";
show(trip); time d3 = { , };
cout << "Three_day total:";
show(sum(trip, d3)); getchar();
}
程序清单7.12+7.13
#include<iostream>
#include<cmath>
using namespace std; struct polar{
double distance;
double angle;
};
struct rect {
double x;
double y;
}; void rect_to_polar(const rect *pxy, polar *pda) {//由于形参是指针而不是结构，所以只能用箭头操作符而不能用点操作符
pda->distance = sqrt( pxy->x*pxy->x + pxy->y*pxy->y );
pda->angle = atan2(pxy->y, pxy->x);
}
void show(const polar *pda) {
const double Rate = 57.29577951;
cout << "distance=" << pda->distance;
cout << ",angle=" << pda->angle*Rate<<" degrees"<<endl;
} void main()
{
rect r;
polar p;
cout << "Enter the x and y value:";
while (cin>>r.x>>r.y)
{
rect_to_polar(&r, &p);
show(&p);
cout << "Next 2 numbers(q to quit):";
}
cout << "Done." << endl;
getchar();
}
程序清单7.14（string对象数组）
#include<iostream>
#include<string>
using namespace std; const int Size = ;
void display(const string s[],int n) {
for (int i = ; i < n; i++)
cout << i+ <<": "<<s[i]<<endl;
} void main()
{
string list[Size];
cout << "Enter your " << Size << " favorite XX" << endl;
for (int i = ; i < Size; i++)
{
cout << i + << ": ";
getline(cin, list[i]);//读取string对象
}
cout << "Your list:" << endl;
display(list, Size);
system("pause");
}
程序清单7.15（array对象）
#include<iostream>
#include<string>
#include<array>
using namespace std; const array<string, > Sname = { "Spring","Summer","Fall","Winter" }; void fill(array<double, > *p) {
for (int i = ; i < ; i++)
{
cout << "Enter " << Sname[i] << " expenses:";
cin >> (*p)[i];//p是地址，*p是array对象，(*p)[i]是array对象里的第（i+1）个double数据
}
}
void show(array<double, > q) {
double sum = 0.0;
cout << "EXPENSES" << endl;
for (int i = ; i < ; i++)
{
cout << Sname[i] << ": $" << q[i] << endl;
sum += q[i];
}
cout << "Sum expenses: $" << sum << endl;
} void main()
{
array<double, > expense;
fill(&expense);
show(expense);
system("pause");
}
程序清单7.16，7.17(递归)
#include<iostream>
using namespace std; void down(int n) {
cout << "Counting down " << n <<",\tn at "<<&n<< endl;
if (n > )
down(n - );
cout << n << ": Kaboom!" << "\t\tn at " << &n << endl;
} void main()
{
down();
system("pause");
}
#include<iostream>
using namespace std; const int Len = ;
const int Div = ;
void subdivide(char ar[],int low,int high,int level) {
if (level == )
return;
int mid = (high + low) / ;
ar[mid] = '|';
subdivide(ar, low, mid, level - );
subdivide(ar, mid, high,level - );
} void main()
{
char ruler[Len];
int i;
for (i = ; i < Len - ; i++)//去掉一个头，两个尾
ruler[i] = ' ';
ruler[Len - ] = '\0';//末尾设置为结束符
int max = Len - ;//倒数第二位（去掉结束符后的末尾）
int min = ;
ruler[min] = ruler[max] = '|';
cout << ruler << endl;
for (i = ; i <=Div; i++)
{
subdivide(ruler, min, max, i);
cout << ruler << endl;
}
system("pause");
}
函数指针
double (*pf)(int);//pf是一个指向函数（函数返回double）的指针
double *pd(int);//pd（）是一个返回double *的函数
函数声明
void aa(int n, double(*pf)(int));
指出，pf是一个函数指针，它指向的函数接受一个int参数，并返回一个double值。
aa(50,函数名) 即可进行调用。
程序清单7.18
#include<iostream>
using namespace std; void estimate(int line,double (*pf)(int)) {
cout << line << " lines will take ";
cout << (*pf)(line) << " hour(s)." << endl;
}
double bet(int lns) {
return 0.05*lns;
}
double pam(int lns) {
return 0.03*lns + 0.0004*lns*lns;;
} void main()
{
int code;
cout << "How many lines? ";
cin >> code;
cout << "Here is Bet's estimate:" << endl;
estimate(code, bet);
cout << "Here is Pam's estimate:" << endl;
estimate(code, pam);
system("pause");
}
函数指针数组
const double * f1(const double ar[], int n);
const double * f2(const double [], int);
const double * f3(const double *, int);//这三行代码的含义完全相同
const double *(*pa[])(const double *, int) = { f1,f2,f3 };//声明，并初始化 *pd[] //an array of 3 pointers
(*pd)[] //a pointer to an array of 3 elements
程序清单7.19
#include<iostream>
using namespace std; const double * f1(const double *ar, int n) { //f1（）是一个返回double类型指针的函数
return ar;//返回的是地址，要得到值得话，必须加上*符号
}
const double * f2(const double ar[], int n) {
return ar + ;
}
const double * f3(const double ar[], int n) {
return ar + ;
} void main()
{
double av[] = { 1112.3,1542.6,2227.9 };
const double *(*p1)(const double *, int) = f1;//p1是函数指针，指向f1函数的地址，*p1（即f1函数）传入double地址和int长度，返回double地址
auto p2 = f2;
cout << "Using pointers to functions:" << endl << "Address Value" << endl;
cout << (*p1)(av, ) << ": " << *(*p1)(av, ) << endl;//*p1表示函数，前者调用函数，返回double值得地址，后者为取出地址所代表的的double值
cout << p2(av, ) << ": " << *p2(av, ) << endl;//p2表示函数 const double *(*pa[])(const double *, int) = { f1,f2,f3 };//声明一个函数指针数组
auto pb = pa;//pa表示函数指针数组的地址
cout << "Using an array of pointers to functions:" << endl << "Address Value" << endl;
for (int i = ; i < ; i++)
cout << pa[i](av, ) << ": " << *pa[i](av, ) << endl;
cout << "Using a pointer to a pointer to a functions:" << endl << "Address Value" << endl;
for (int i = ; i < ; i++)
cout << pb[i](av, ) << ": " << *pb[i](av, ) << endl; cout << "Using pointers to an array of pointers :" << endl << "Address Value" << endl;
auto pc = &pa;
cout << (*pc)[](av, ) << ": " << *(*pc)[](av, ) << endl;
const double *(*(*pd)[])(const double *, int) = &pa;//参见23行，pd表示pa的地址，所以在23行定义的基础上再多一个*号
const double * pdb = (*pd)[](av, );//(*pd)=pa,pdb表示av[1]的地址
cout << pdb << ": " << *pdb << endl;
cout << (*(*pd)[])(av, ) << ": " << *(*(*pd)[])(av, ) << endl;//(*pd)=pa,(*(*pd)[2])=（*pa[2]）表示函数指针数组的第三个指针元素 system("pause");
}