std::experimental::basic_string_view::to_string, std::experimental::basic_string_view::operator basic_string
From cppreference.com
                    
                                        
                    < cpp | experimental | basic string view
                    
                                                            
                    |   template<class Allocator = allocator<CharT>> 
basic_string<CharT, Traits, Allocator>  | 
(library fundamentals TS) | |
|   template<class Allocator> 
explicit operator basic_string<CharT, Traits, Allocator>() const;  | 
(library fundamentals TS) | |
Creates a basic_string with a copy of the content of the current view.
Contents | 
[edit] Template parameters
| Allocator | - |   Allocator type used to allocate internal storage
 | 
[edit] Parameters
| a | - | Allocator instance to use for allocating the new string | 
[edit] Return value
A basic_string containing a copy of the characters of the current view.
[edit] Complexity
Linear in size()