【C++ Primer】标准库string类型

/**标准库string类型*Zhi-Yun Deng*2013-11-01*/#include <iostream>#include <string> //标准库string类型头文件#include <cctype> //string对象中字符的处理函数的头文件using std::string; //string类型的using声明using std::cin;using std::cout;using std::endl;int main(){    int n = 4;    string s1; //默认构造函数，s1为空串    string s2(s1); //将s2初始化为s1的一个副本    string s3("value"); //将s3初始化为一个字符串字面值副本    string s4(n, 'c'); //将s4初始化为字符‘c’的n个副本    cout << "1、string对象的定义和初始化" << endl;    cout << "s1: " << s1 << endl;    cout << "s2: " << s2 << endl;    cout << "s3: " << s3 << endl;    cout << "s4: " << s4 << endl;    cout << "****************************************\n" << endl;    cout << "2、string对象的读写" << endl;    string word;    while(cin >> word)    {        cout << "读入未知数目的string对象，word：" << word << endl;        if(word == "break")            break;    }    string line;    while(getline(cin, line))    {        cout << "用getline读取整行文本，line：" << line << endl;        if(line == "break")            break;    }    cout << "****************************************\n" << endl;    cout << "3、string对象的操作" << endl;    string st("The expense of spirit\n");    cout << "The size of " << st << "is " << st.size()         << " characters, including the newline" << endl;    if(!st.size()==0)        cout << st.size() << endl;    if(!st.empty())        cout << st.size() << endl;    s2 = s3;    cout << "string对象的赋值，s2=s3，s2：" << s2 << endl;    s1 = "hello";    s2 = "world";    s3 = s1 + ", ";    s4 = s1 + ", " + "world";    cout << "s1: " << s1 << "\t size: "<< s1.size() << endl;    cout << "s2: " << s2 << "\t size: "<< s2.size() << endl;    cout << "s3: " << s3 << "\t size: "<< s3.size() << endl;    cout << "s4: " << s4 << "\t size: "<< s4.size() << endl;    for(string::size_type ix=0; ix!=s4.size(); ++ix)        cout << s4[ix] << endl;    for(string::size_type ix=0; ix!=s4.size(); ++ix)        s4[ix]='*';    cout << "s4: " << s4 << "\t size: "<< s4.size() << endl;    cout << "****************************************\n" << endl;    cout << "4、string对象中字符的处理" << endl;    string testStr("123abcABC *&^%$#@()-+=,.;'?/\n\t\r!~");    string::size_type alnum_cnt(0); //统计字母或数字的个数    string::size_type alpha_cnt(0); //统计字母的个数    string::size_type digit_cnt(0); //统计数字的个数    string::size_type print_cnt(0); //统计可打印字符的个数    string::size_type graph_cnt(0); //统计除空格外可打印的字符的个数    string::size_type space_cnt(0); //统计空白字符的个数    string::size_type lower_cnt(0); //统计小写字母的个数    string::size_type upper_cnt(0); //统计大写字母的个数    string::size_type punct_cnt(0); //统计标点符号的个数    string::size_type cntrl_cnt(0); //统计控制字符的个数    string::size_type xdigit_cnt(0); //统计十六进制数的个数    cout << "testStr的字符个数：" << testStr.size() << endl;    for(string::size_type index=0; index!=testStr.size(); ++index)    {        if(isalnum(testStr[index]))            ++alnum_cnt;        if(isalpha(testStr[index]))            ++alpha_cnt;        if(isdigit(testStr[index]))            ++digit_cnt;        if(isprint(testStr[index]))            ++print_cnt;        if(isgraph(testStr[index]))            ++graph_cnt;        if(isspace(testStr[index]))            ++space_cnt;        if(islower(testStr[index]))            ++lower_cnt;        if(isupper(testStr[index]))            ++upper_cnt;        if(ispunct(testStr[index]))            ++punct_cnt;        if(iscntrl(testStr[index]))            ++cntrl_cnt;        if(isxdigit(testStr[index]))        {            cout << testStr[index] << endl;            ++xdigit_cnt;        }    }    cout << "alnum_cnt: " << alnum_cnt << endl;    cout << "alpha_cnt: " << alpha_cnt << endl;    cout << "digit_cnt: " << digit_cnt << endl;    cout << "print_cnt: " << print_cnt << endl;    cout << "graph_cnt: " << graph_cnt << endl;    cout << "space_cnt: " << space_cnt << endl;    cout << "lower_cnt: " << lower_cnt << endl;    cout << "upper_cnt: " << upper_cnt << endl;    cout << "punct_cnt: " << punct_cnt << endl;    cout << "cntrl_cnt: " << cntrl_cnt << endl;    cout << "xdigit_cnt: " << xdigit_cnt << endl;    for(string::size_type index=0; index != testStr.size(); ++index)        testStr[index] = tolower(testStr[index]);    cout << "tolower: " << testStr << endl;    for(string::size_type index=0; index != testStr.size(); ++index)        testStr[index] = toupper(testStr[index]);    cout << "toupper: " << testStr << endl;    cout << "****************************************\n" << endl;    return 0;}