c++名字空间，C与C++字符串的区别，枚举类型

            1：命名空间
2：C与C++字符串的区别和基本操作
3：枚举类型
命名空间
            
#include <string>    
#include <ctype.h>
#include <vector>
#include <iostream>  
#include <fstream>


// using declarations states our intent to use these names from the namespace std    usingnamespace  std;
namespace one{
    string name = "namesapce one的name";
}
namespace two{
    string name = "namesapce two的name";
}

string name = "全局的name";
int main()
{

　　//using one::name;//不行，同一范围内重定义，与下面的name有冲突
    cout << one::name << endl;
    cout << two::name << endl;
    
    string name = "局部name";
    cout << name << endl;
    cout << ::name << endl; //全局没有范围。没有放在名字空间中的东西都成为放在匿名名字空间，
    //匿名就是没有名字，直接用双冒号表示，表示全局的或者外面的/*    system("pause");*/return0;
}

#include <string>    
#include <ctype.h>
#include <vector>
#include <iostream>  
#include <fstream>


// using declarations states our intent to use these names from the namespace std    usingnamespace  std;
void printString(char *s1, char *s2);
int main()
{
    char cs1[30] = "i am cool"; //最多存29个字符，最后一个必须为结尾符,如果定义为csa[9]会出错，没把结尾符算进去char cs2[30] = "you are cool";
    
    printString(cs1, cs2);
    strcpy(cs2, cs1);
    printString(cs1, cs2);

    cout << "cs1与cs2比较后的结果，返回值为0，-1,1"<<strcmp(cs1, cs2)<< endl;
    cout << "cs2的长度为(不包括结尾符) "<<strlen(cs2) << endl;
    cout << "将cs1的附加到cs1后面"<<strcat(cs1, cs2) << endl;
    cout << cs1 << endl;
    return0;
}

void printString(char *s1,char *s2)
{
    cout << "s1= "<<s1 << "   s2= "<< s2 << endl;
}

#include <string>    
#include <ctype.h>
#include <vector>
#include <iostream>  
#include <fstream>


// using declarations states our intent to use these names from the namespace std    usingnamespace  std;
void printString(string s1, string s2);
int main()
{
    string cpps1 = "i am cool";
    string cpps2 = "you are cool";

　　  string::size_type index= cpps1.find("i");//查找第一个字符出现的位置
　　  cout << index << endl;

            　　const char*s1 = cpps1.c_str();// c++风格转换为c风格
    printString(cpps1, cpps2);
    cpps1 = cpps2; 
    printString(cpps1, cpps2);

/*    cout << "cs1与cs2比较后的结果，返回值为0，-1,1"<<strcmp(cs1, cs2)<< endl;*/
    cout << "cs2的长度为(不包括结尾符) "<<cpps2.size() << endl;
    cout << "将cs1的附加到cs1后面"<< cpps1+cpps2<< endl;
    cout << cpps1 << endl;
    cout << "将cs1的附加到cs1后面" << (cpps1+=cpps2) << endl;
    cout << cpps1 << endl;
    return0;
}

void printString(string s1,string s2)
{
    cout << "s1= "<<s1 << "   s2= "<< s2 << endl;
}

#include <string>    
#include <ctype.h>
#include <vector>
#include <iostream>  
#include <fstream>


// using declarations states our intent to use these names from the namespace std    usingnamespace  std;
enum Color{BLACK,WHITE,GREEN,YELLOW,RED};
enum Color_me{ BLACK_me, WHITE_me, GREEN_me, YELLOW_me, RED_me };

int main()
{
    int v;
    Color c; //c里面的数字虽然看上去像整型，但是是Color型，比整型的范围要小    Color_me c2;
    c = BLACK;
    cout << c << endl; //输出0
    v = c; //将范围小的BLACK复制到Int类型是可行的
    cout << v << endl;
    //c = v; //将int类型变为BLACK类型不可行，缩小了范围。
    //c2 = c; //两个不同的枚举类型之间的值得类型也是不同的，不可以相互赋值return0;
}