boost库之字符串与文本处理——lexical

#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 * */