std::valarray<T>::operator+,-,~,!
From cppreference.com
                    
                                        
                    
                    
                                                            
                    |   valarray<T> operator+() const;  | 
(1) | |
|   valarray<T> operator-() const;  | 
(2) | |
|   valarray<T> operator~() const;  | 
(3) | |
|   valarray<bool> operator!() const;  | 
(4) | |
Applies unary operators to each element in the numeric array.
Parameters
(none)
Return value
A numeric array containing elements with values obtained by applying corresponding operator to the values in *this.
Exceptions
(none)
Notes
Each of the operators can only be instantiated if the following requirements are met:
-  The indicated operator can be applied to type 
T -  The result value can be unambiguously converted to 
T(1-3) or bool (4). 
-  The indicated operator can be applied to type 
 
The function can be implemented with the return type different from std::valarray. In this case, the replacement type has the following properties:
- All const member functions of std::valarray are provided.
 - std::valarray, std::slice_array, std::gslice_array, std::mask_array and std::indirect_array can be constructed from the replacement type.
 - All functions accepting an argument of type const std::valarray& except begin() and end() (since C++11) should also accept the replacement type.
 - All functions accepting two arguments of type const std::valarray& should accept every combination of const std::valarray& and the replacement type.
 - The return type does not add more than two levels of template nesting over the most deeply-nested argument type.