boost/lexical_cast.hpp的简单使用方法_学着站在巨人的肩膀上_百度空间

1、字符串->数值

C++代码

1. #include <boost/lexical_cast.hpp>
2. #include <iostream>
3. int main()
4. {
5. using boost::lexical_cast;
6. int a = lexical_cast<int>("123");
7. double b = lexical_cast<double>("123.12");
8. std::cout<<a<<std::endl
9. std::cout<<b<<std::endl;
10. return 0;
11. }

#include <boost/lexical_cast.hpp>#include <iostream>int main(){ using boost::lexical_cast; int a = lexical_cast<int>("123"); double b = lexical_cast<double>("123.12"); std::cout<<a<<std::endl std::cout<<b<<std::endl; return 0;}

2、数值->字符串

C++代码

1. #include <boost/lexical_cast.hpp>
2. #include <string>
3. #include <iostream>
4. int main()
5. {
6. using std::string;
7. const double d = 123.12;
8. string s = boost::lexical_cast<string>(d);
9. std::cout<<s<<std::endl;
10. return 0;
11. }

#include <boost/lexical_cast.hpp>#include <string>#include <iostream>int main(){ using std::string; const double d = 123.12; string s = boost::lexical_cast<string>(d); std::cout<<s<<std::endl; return 0;}

3、异常

C++代码

1. #include <boost/lexical_cast.hpp>
2. #include <iostream>
3. int main()
4. {
5. using std::cout;
6. using std::endl;
7. int i;
8. try
9. {
10. i = boost::lexical_cast<int>("xyz");
11. }
12. catch(boost::bad_lexical_cast& e)
13. {
14. cout<<e.what()<<endl;
15. return 1;
16. }
17. cout<<i<<endl;
18. return 0;
19. }

#include <boost/lexical_cast.hpp>#include <iostream>int main(){ using std::cout; using std::endl; int i; try { i = boost::lexical_cast<int>("xyz"); } catch(boost::bad_lexical_cast& e) { cout<<e.what()<<endl; return 1; } cout<<i<<endl; return 0;}

显然“xyz”并不能转换为一个int类型的数值，于是抛出异常，捕捉后输出“bad lexical cast: source type value could not be interpreted as target”这样的信息。

4、注意事项

lexical_cast依赖于字符流std::stringstream，其原理相当简单：把源类型读入到字符流中，再写到目标类型中，就大功告成。

C++代码

1. int d = boost::lexical_cast<int>("123");

int d = boost::lexical_cast<int>("123");

相当于

C++代码

1. int d;
2. std::stringstream s;
3. s<<"123";
4. s>>d;

int d;std::stringstream s;s<<"123";s>>d;

5、小结

我们已经体验了boost::lexcial_cast。当然，lexical_cast不仅仅局限于字符串类型与数值类型之间的转换：可在任意可输出到stringstream的类型和任意可从stringstream输入的类型间转换。

；-）