std::queue<T,Container>::front
From cppreference.com
                    
                                        
                    
                    
                                                            
                    |   reference front();  | 
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|   const_reference front() const;  | 
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Returns reference to the first element in the queue. This element will be the first element to be removed on a call to pop(). Effectively calls c.front().
Parameters
(none)
Return value
Reference to the first element.
Complexity
Constant
See also
|    access the last element   (public member function)  | |
|    removes the first element   (public member function)  |