C++ 11字符数组/字符串/数字转换/字符串拼接

#include<string>
#include<typeinfo>

int num = 123;
string num2str = to_string(num);
cout << typeid(to_string(num) == typeid(string) << endl;  // true

#include<sstream>

double num = 123.56;  // float同理
stringstream sstream;
sstream << num;
string num2str = sstream.str();  // num2str = "123.56"
cout << typeid(sstream.str() == typeid(string) << endl;  // true
sstream.clear();  // 若在用一个流中处理大量数据，则需手动清除缓存，小数据或不同流可忽略

string str = "456.78";
double num;        // float同理,int需要str为整数,否则报错
stringstream sstream(str);
sstream >> num;    // num = 456.78
cout << typeid(num == typeid(double) << endl;  // true

#include<string>

string str = "456.78";
double num = stod(str);   // num = 456.78    
cout << typeid(num == typeid(double) << endl;  // true

#include<cstdio>

char ch[100] = "-456.78";
// 注：atof(ch)只返回double数字，因此需要float可以自行转换成float
double num = atof(ch);   // num = -456.78   
cout << typeid(num == typeid(double) << endl;  // true

char ch[100] = "Hellow World";
string str = ch;  // str = "Hellow World"
cout << typeid(str == typeid(string) << endl;  // true

string str = "Hellow World";  
char ch[100] = {0};
for (int i=0;i < str.length();i++)
	ch[i] = str[i];
cout << ch << endl;  // ch = "Hellow World"

string str1 = "aaa";
strint str2 = "bbb";
cout << str1 + str2 << endl; // "aaabbb"
cout << str1 + "bbb" << endl; // "aaabbb"

string str1 = "aaa";
char* str2 = "bbb";
cout << str1 + str2 << endl; // "aaabbb"