Talend - 缺少输出(Talend - missing output)

 std::string不是内置类型，所以s[3]中s[3] operator [] s[3]是对字符串模板中定义该运算符的成员函数的调用。 
 
 您可以通过查找operator []的参考页找到该类型： 
 
 
 
 返回指定位置pos处字符的引用。 
 
 
 要从文档中查找类型reference和const_reference ，请参阅std::basic_string<CharT>模板的 “成员类型”部分。 
 
 如果您正在寻找从位置3开始的长度为1的std::string ，请改为使用substr ： 
 
s.substr(3, 1); // This produces std::string containing "c"

std::string is not a built-in type, so operator [] in s[3] is a call to a member function defining this operator in the string template.
 
You can find the type by looking up the reference page for operator []:
 
 
 
Returns a reference to the character at specified location pos.
 
 
To look up the type reference and const_reference from the documentation see "member types" section of std::basic_string<CharT> template.
 
If you are looking for std::string of length 1 starting at location 3, use substr instead:
 
s.substr(3, 1); // This produces std::string containing "c"