[C++ Primer Plus] 第4章、复合类型（一）程序清单—

程序清单4.1

 #include<iostream>

 using namespace std;

 void main(){

     int yams[];

     yams[]=;

     yams[]=;

     yams[]=;

     int yams_cost[]={,,}; 

     cout<<"Total yams="<<yams[]+yams[]+yams[]<<endl;

     cout<<"The package with "<<yams[]<<" yams costs "<<yams_cost[]<<" cents per yam"<<endl;

     cout<<"Total costs="<<yams[]*yams_cost[]+yams[]*yams_cost[]+yams[]*yams_cost[]<<" cents"<<endl;

     cout<<"Size of yams array="<<sizeof(yams)<<" bytes"<<endl;

     cout<<"Size of yams[0]="<<sizeof(yams[])<<" bytes"<<endl;

     system("pause");

 }

程序清单4.2

 #include<iostream>

 #include<cstring>//strlen(),c语言版为string.h

 using namespace std;

 void main(){

     const int size=;

     char name1[size];//char占一个字节

     char name2[size]="C++owboy";

     cout<<"I am "<<name2<<".What's your name?"<<endl;

     cin>>name1;

     cout<<"Well,"<<name1<<",your name has "<<strlen(name1)<<" letters and is stored in an array of "<<sizeof(name1)<<" bytes"<<endl;

     cout<<"Your initial is "<<name1[]<<endl;

     name2[]='\0';

     cout<<"Here are the first 3 characters of my name:"<<name2<<endl;

     system("pause");

 }

程序清单4.3

 #include<iostream>

 using namespace std;

 void main(){

     const int size=;

     char name[size];

     char dessert[size];

     cout<<"What's your name?"<<endl;

     cin>>name;

     cout<<"What's your favorate dessert?"<<endl;

     cin>>dessert;

     cout<<"I have some delicious "<<dessert<<" for you."<<endl;

     system("pause");

 }

注意：cin使用空白（空格、制表符和换行符）来确定字符串的结束位置，所以cin将Alise放在了name数组，将dreeb放在了dessert数组

为了解决这种问题，C++提供getline()和get()方法，如下所示：

程序清单4.4

 #include<iostream>

 using namespace std;

 void main(){

     const int size=;

     char name[size];

     char dessert[size];

     cout<<"What's your name?"<<endl;

     cin.getline(name,size);

     cout<<"What's your favorate dessert?"<<endl;

     cin.getline(dessert,size);

     cout<<"I have some delicious "<<dessert<<" for you."<<endl;

     system("pause");

 }

程序清单4.6

 #include<iostream>

 using namespace std;

 void main(){

     cout<<"你房子哪一年修的?"<<endl;

     int year;

     cin>>year;

     cout<<"房子的地址?"<<endl;

     char address[];

     cin.getline(address,);

     cout<<"Year built:"<<year<<endl<<"Address:"<<address<<endl<<"Done!";

     system("pause");

 }

用户没有输入地址的机会，问题在于：cin读取年份后，将回车键生成的换行符留在了队列中，后面的cin.getline()看到换行符后，将认为是一个空行。解决如下：

　　cin>>year;

　　cin.get();

程序清单4.7(string和数组)

 #include<iostream>

 #include<string>

 using namespace std;

 void main(){

     char ch1[];

     char ch2[]="jaguar";

     string str1;

     string str2="panther";

     cout<<"enter a kind of feline:";

     cin>>ch1;

     cout<<"enter another kind of feline:";

     cin>>str1;

     cout<<"Here are some felines:\n"<<ch1<<" "<<ch2<<" "<<str1<<" "<<str2<<endl;

     cout<<"The third letter in "<<ch2<<" is "<<ch2[]<<endl;

     cout<<"The third letter in "<<str2<<" is "<<str2[]<<endl;

     system("pause");

 }

程序清单4.8(string赋值、拼接和附加)

 #include<iostream>

 #include<string>

 using namespace std;

 void main(){

     string str="penguin";

     string str2,str3,str4;

     str2=str;

     cout<<"str2="<<str2<<endl;

     str3="buzzard";

     cout<<"str3="<<str3<<endl;

     str4=str+str3;

     cout<<"str4="<<str4<<endl;

     str+=str3;

     cout<<"str="<<str<<endl;

     str2+=" is cute!";

     cout<<"str2="<<str2<<endl;

     system("pause");

 }

程序清单4.9（cstring）

 #include<iostream>

 #include<string>

 #include<cstring>//strcpy,strcat,strlen

 using namespace std;

 void main(){

     char ch1[];

     char ch2[]="jaguar";

     string str1;

     string str2="panther";

     str1=str2;

     strcpy(ch1,ch2);

     str1+=" paste";

     strcat(ch1," juice");

     int len1=str1.size();

     int len2=strlen(ch1);

     cout<<"the string "<<str1<<" contains "<<len1<<"  characters"<<endl;

     cout<<"the string "<<ch1<<" contains "<<len2<<"  characters"<<endl;

     system("pause");

 }

程序清单4.10

 #include<iostream>

 #include<string>

 #include<cstring>

 using namespace std;

 void main(){

     char ch[];

     string str;

     cout<<"Length of string in ch before input:"<<strlen(ch)<<endl;

     cout<<"Length of string in str before input:"<<str.size()<<endl;

     cout<<"Enter a line of text:"<<endl;

     cin.getline(ch,);

     cout<<"You entered:"<<ch<<endl;

     cout<<"Enter another line of text:"<<endl;

     getline(cin,str);

     cout<<"You entered:"<<str<<endl;

     cout<<"Length of string in ch after input:"<<strlen(ch)<<endl;

     cout<<"Length of string in str after input:"<<str.size()<<endl;

     system("pause");

 }

注意：未初始化的数组内容未定，strlen（）从数组中的第一个元素开始计算字节数，直到遇到空字符。在本例中数组内并未有空字符，所以字节数甚至超过了数组长度；未初始化的string对象长度置0

程序清单4.11+4.12(结构体)

 #include<iostream>

 using namespace std;

 struct  table{

     char name[];

     float volumn;

     double price;

 };

 void main(){

     table guest={"GG",1.88,29.99};

     table pal={"AA",3.12,32.99};

     cout<<"Expand your guest list with "<<guest.name<<" and "<<pal.name<<endl;

     cout<<"You can have both for  $"<<guest.price+pal.price<<endl;

     cout<<"------------------------------"<<endl;

     table choice=guest;

     cout<<"choice:"<<choice.name<<" for $"<<choice.price<<endl;

     system("pause");

 }

程序清单4.13

 #include<iostream>

 using namespace std;

 struct  table{

     char name[];

     float volumn;

     double price;

 };

 void main(){

     table guest[]={

         {"GG",1.88,29.99},

         {"AA",3.12,32.99}

     };

     cout<<"The guests "<<guest[].name<<" and "<<guest[].name<<endl<<"have a combined volumn of "<<guest[].volumn+guest[].volumn<<" cubic feet"<<endl;

     system("pause");

 }

程序清单4.17(指针：new)

 #include<iostream>

 using namespace std;

 void main(){

     int nights=;

     int *pt = new int;

     *pt = ;

     double *pd = new double;

     *pd = 100000000000.1;

     cout << "nights value=" << nights << ":location " << &nights << endl;

     cout << "int value=" <<*pt<< ":location " <<pt<< endl;

     cout << "double value=" << *pd << ":location " << pd << endl;

     cout << "location of pointer pd:" << &pd<< endl;

     cout << "size of pt=" <<sizeof(pt)<< endl;

     cout << "size of *pt=" << sizeof(*pt) << endl;

     cout << "size of pd=" << sizeof(pd) << endl;

     cout << "size of *pd=" << sizeof(*pd) << endl;

     system("pause");

 }

程序清单4.18(new完之后要delete)

 #include<iostream>

 using namespace std;

 void main() {

     double *p = new double[];//使用new创建动态数组

     p[] = 0.2;

     p[] = 0.5;

     p[] = 0.8;

     cout << "p[1]=" << p[] << endl;

     p++;

     cout << "Now p[0]=" << p[] << endl;

     cout << "p[1]=" << p[] << endl;

     p--;

     cout << "And now p[0]=" << p[] << endl;

     delete[] p;//回归初始位置释放内存

     getchar();

 }

程序清单4.19

 #include<iostream>

 using namespace std;

 void main() {

     double wages[] = { 10000.0,20000.0, 30000.0 };

     short stacks[] = {  ,  ,  };

     double * pw = wages;

     short * ps = &stacks[];

     cout << "pw=" << pw <<",*pw="<<*pw<< endl;

     pw++;

     cout << "Now,pw=" << pw << ",*pw=" << *pw << endl;

     cout << "ps=" << ps << ",*ps=" << *ps << endl;

     ps++;

     cout << "Now,ps=" << ps << ",*ps=" << *ps << endl;

     cout << "stacks[0]=" << stacks[] << ",stacks[1]=" << stacks[] << endl;

     cout << "*stacks=" << *stacks<< ",*(stacks+1)=" << *(stacks + ) << endl;

     cout << "sizeof(wages)=" << sizeof(wages)<< endl;

     cout << "sizeof(pw)=" << sizeof(pw) << endl;

     getchar();

 }

程序清单4.20

 #define _CRT_SECURE_NO_WARNINGS

 #include<iostream>

 #include<cstring>

 using namespace std;

 void main() {

     char animal[] = "bear";

     const char * bird = "wren";

     char * ps;

     cout << animal <<" and "<< bird << endl;

     cout << "Enter a kind of animal:";

     cin >> animal;

     ps = animal;

     cout << "ps="<<ps<< endl;

     cout << "Before using strcpy()： \n ";

     cout << animal << " at " << (int *)animal << endl;

     cout << ps << " at " << (int *)ps << endl;

     ps = new char[strlen(animal) + ];

     strcpy(ps, animal);

     cout << "After using strcpy()： \n ";

     cout << animal << " at " << (int *)animal << endl;

     cout << ps << " at " << (int *)ps << endl;

     delete[] ps;

     system("pause");

 }

程序清单4.21

 #include<iostream>

 using namespace std;

 struct inflatable {

     char name[];

     float volumn;

     double price;

 };

 void main() {

     inflatable *ps = new inflatable;

     cout <<"Enter name of inflatable item:";

     cin.get(ps->name,);

     cout << "Enter volumn in cubic feet:";

     cin>>(*ps).volumn;

     cout << "Enter price:$";

     cin >>ps->price;

     cout << "Name:" << (*ps).name<< endl;

     cout << "Volumn:" <<ps->volumn<< endl;

     cout << "Price:" <<ps->price<< endl;

     delete ps;

     system("pause");

 }

程序清单4.22

 #include<iostream>

 #include<cstring>

 using namespace std;

 char * getname() {

     char temp[];

     cout << "Enter last name:";

     cin>>temp;

     char *pn = new char[strlen(temp) + ];//长度+1：包括一个空字符

     strcpy(pn, temp);

     return pn;

 }

 void main(){

     char * name;

     name = getname();

     cout << name << " at " << (int *) name << endl;

     delete[] name;

     name = getname();

     cout << name << " at " << (int *) name << endl;

     delete[] name;

     system("pause");

 }

两次地址可能相同，也可能不同。

程序清单4.23（类型组合）

 #include<iostream>

 #include<cstring>

 using namespace std;

 struct Student {

     int age;

 };

 void main(){

     Student s1, s2, s3;

     s1.age = ;

     Student *p = &s2;

     p->age = ;

     Student ss[];

     ss[].age = ;

     cout << "ss[0].age=" << ss->age << endl;

     const Student * arp[] = { &s1,&s2,&s3 };//指针数组：由指针组成的数组

     cout << "s1.age="<<arp[]->age<< endl;

     const Student **ppa = arp;//arp是数组名称，即第一个元素的地址，而第一个元素为指针，所以ppa是二级指针

     auto ppb = arp;//自动推断类型

     cout << "s1.age=" << (*ppa)->age << endl;

     cout << "s2.age=" << (*(ppa+))->age<< endl; //ppa + 1指向arp[1]，即&s2

     //cout << "s2.age=" << (*ppa + 1)->age << endl;        错误！

     system("pause");

 }

程序清单4.24(数组的替代品，array，vector)

 #include<iostream>

 #include<vector>

 #include<array>

 using namespace std;

 void main() {

     double a[] = { 1.2,2.4,3.6,4.8 };

     vector<double> b();

     b[] = 1.0 / 3.0;

     b[] = 1.0 / 5.0;

     b[] = 1.0 / 7.0;

     b[] = 1.0 / 9.0;

     array<double, > c = { 3.14,2.72,1.62,1.41 };

     array<double, > d;

     d = c;

     cout << "a[2]:" << a[] << " at " << &a[]<<  endl;//&a[2]=a + 2

     cout << "b[2]:" << b[] << " at " << &b[] << endl;

     cout << "c[2]:" << c[] << " at " << &c[] << endl;

     cout << "d[2]:" << d[] << " at " << &d[] << endl<<endl;

     a[-] = 20.2;//a[-2]=*(a-2)

     cout << "a[2]:" << a[-]<< " at " << &a[-]<< endl;

     cout << "c[2]:" << c[] << " at " << &c[] << endl;

     cout << "d[2]:" << d[] << " at " << &d[] << endl;

     system("pause");

 }

注意：无论是数组，vector还是array对象，都可以使用数组表示法来访问各个元素。其次，从地址可知，array和数组都是存储在栈中，而vector存储在自由存储区或堆中。第三，可以将array对象赋给另一个array对象；而对于数组，必须逐元素复制。

索引-2转换为：a[-2]=*(a-2)

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[C++ Primer Plus] 第4章、复合类型（一）程序清单——指针new和delete