std::sub_match::operator string_type, std::sub_match::str
From cppreference.com
                    
                                        
                    
                    
                                                            
                    |   operator string_type() const;  | 
(1) | |
|   string_type str() const;  | 
(2) | |
Converts to an object of the underlying std::basic_string type.
The first version is an implicit conversion, the second one is explicit.
Contents | 
[edit] Parameters
(none)
[edit] Return value
Returns the matched character sequence as an object of the underlying std::basic_string type.  If the matched member is false then the empty string is returned.
[edit] Complexity
Linear in the length of the underlying character sequence.
[edit] Example
std::ssub_match sm; std::string s = sm; // implicit conversion std::cout << s.length() << '\n';
Output:
0