25 Numerics library [numerics]

25.7 Numeric arrays [numarray]

25.7.2 Class template valarray [template.valarray]

25.7.2.6 Unary operators [valarray.unary]

valarray operator+() const; valarray operator-() const; valarray operator~() const; valarray<bool> operator!() const;
Requires: Each of these operators may only be instantiated for a type T to which the indicated operator can be applied and for which the indicated operator returns a value which is of type T (bool for operator!) or which may be unambiguously implicitly converted to type T (bool for operator!).
Returns: A valarray whose length is size().
Each element of the returned array is initialized with the result of applying the indicated operator to the corresponding element of the array.