boost 字符串与文本处理 -> lexical_cast

lexical_cast P178

1. 示例代码

       #include <boost/lexical_cast.hpp>
       int main()
       {
           using namespace boost;
           int x = lexical_cast<int>("100");
           long y = lexical_cast<long>("2000");
           float pai = lexical_cast<float>("3.14159e5");
           double e = lexical_cast<double>("2.71828");
   
           cout<< x << y << pai << e << endl;
   
           string str = lexical_cast<string>(456);
           cout<<str<<endl;
           cout<<lexical_cast<string>(0.618)<<endl;
           cout<<lexical_cast<string>(0x10)<<endl;
       }

2. 异常bad_lexical_cast
   当lexical_cast无法执行转换操作时会抛出异常bad_lexical_cast。我们可以利用bad_lexical_cast来验证数字符串的合法性，实现一个模板函数num_valid()的代码如下：

           template<typename T>
           bool num_valid(const char* str)
           try
           {
               lexical_cast<T>(str);
               return true;
           }
           catch(bad_lexical_cast&)
           {
               return false;
           };

3. 应用于自己的类

   示范

   class demo_class
   {
       friend std::ostream& operator<<(std::ostream& os, const demo_class& x)
       {
       os<<"demo_class's Name";
       return os;
       }
   };
   
   int main()
   {
       cout << lexical_cast<string>(demo_class())<<endl;
   }

   模板类 输出类名

       template<typename T>
       struct outable
       {
           friend std::ostream& operator<<(std::ostream& os, const T& x)
           {
               os <<typeid(T).name();
               return os;
           }
       };
   
       class demo_class:outable<demo_class>{};
       int main()
       {
           cout<<lexical_cast<string>(demo_class())<<endl;
       }