std::valarray::operator+,-,~,!(3)

NAME
std::valarray::operator+,-,~,! - std::valarray::operator+,-,~,!

Synopsis
   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
   May throw implementation-defined exceptions.

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 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.
     * For every function taking a const std::valarray<T>&
       except begin() and end()
       (since C++11), identical functions taking the replacement types shall be added;
     * For every function taking two const std::valarray<T>& arguments, identical
       functions taking every combination of const std::valarray<T>& and replacement
       types shall be added.
     * The return type does not add more than two levels of template nesting over the
       most deeply-nested argument type.

Example
// Run this code
 #include <iostream>
 #include <string_view>
 #include <valarray>
 template<typename T>
 void print(std::string_view const note,
            std::valarray<T> const vala, // by-value, see Notes above
            std::string_view const term = "\n")
 {
     std::cout << note << std::boolalpha << std::showpos;
     for (T const element : vala)
         std::cout << '\t' << element;
     std::cout << term;
 }
 int main()
 {
     std::valarray<int> x{1, 2, 3, 4};
     print<int>("x: ", x);
     print<int>("+x: ", +x);
     print<int>("+ + x: ", + + x);
     print<int>("-x: ", -x);
     print<int>("- - x: ", - - x, "\n\n");
     std::valarray<short> y{0, 1, -1, 0x7fff};
     print<short>("y: ", y);
     print<short>("~y: ", ~y);
     print<short>("~~y: ", ~~y, "\n\n");
     std::valarray<bool> z{true, false};
     print<bool>("z: ", z);
     print<bool>("!z: ", !z);
     print<bool>("!!z: ", !!z);
 }

Possible output:
 x: +1 +2 +3 +4
 +x: +1 +2 +3 +4
 + + x: +1 +2 +3 +4
 -x: -1 -2 -3 -4
 - - x: +1 +2 +3 +4
 y: +0 +1 -1 +32767
 ~y: -1 -2 +0 -32768
 ~~y: +0 +1 -1 +32767
 z: true false
 !z: false true
 !!z: true false

See also
   operator+=
   operator-=
   operator*=
   operator/=
   operator%= applies compound assignment operator to each element of the valarray
   operator&= (public member function)
   operator|=
   operator^=
   operator<<=
   operator>>=
   operator+
   operator-
   operator*
   operator/
   operator% applies binary operators to each element of two valarrays, or a valarray
   operator& and a value
   operator| (function template)
   operator^
   operator<<
   operator>>
   operator&&
   operator||

Hidden category:
     * Pages with unreviewed LWG DR marker