std::valarray::size
From cppreference.com
                    
                                        
                    
                    
                                                            
                    | std::size_t size() const; | ||
Returns the number of elements in the valarray.
| Contents | 
[edit] Parameters
(none)
[edit] Return value
Number of elements in the valarray.
[edit] Example
| This section is incomplete Reason: no example | 
[edit] See also
| changes the size of valarray (public member function) |