boost库之字符串与文本处理——lexical_cast

#include <iostream>#include <string>#include <vector>#include <set>#include <map>#include <algorithm>#include <boost/lexical_cast.hpp>#include <boost/assert.hpp>using namespace boost;using namespace std;template<typename T>bool num_valid(const char* str){     try     {          lexical_cast<T>(str); //尝试转换数字          return true;     }catch(bad_lexical_cast&){         return false;     }}class demo_class{friend std::ostream& operator<<(std::ostream& os,const demo_class& x){     os << "demo_class's Name";     return os;}};int main( int argc,char **argv){    /*常用操作*/    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;    /*抛出异常*/        try    {         cout << lexical_cast<int>("0x100");         cout << lexical_cast<double>("helloworld");         cout << lexical_cast<bool>("false");         cout << lexical_cast<long>("1000L");    }catch (bad_lexical_cast& e)    {         cout <<"error:" << e.what()<< endl;    }    /*验证字符串的合法性*/    assert(num_valid<double>("3.14"));    assert(!num_valid<int>("3.14"));    assert(num_valid<int>("65535"));    cout << lexical_cast<string>("demo_class") << endl;     return (0);}/*注意： *1.lexical_cast转换成数字的字符串只能有数字和小数点，不能出现除(表示e/E除外)字母或其他非数字字符 *2.它不支持高级的格式控制，如有需要应使用std::stringstream或者boost::format *3.可以转换bool类型，不能使用true/false.只能使用1或0 *4.*//*对转换对象的要求： * 1.转换起点对象是可流输出的，即定义了operator<<; * 2.转换终点对象是可流输入的，即定义了operator>>; * 3.转换终点对象必须是可缺省构造和可拷贝的 * */