Does the unary + operator have any practical use?

Question

Was the unary + operator only included for symmetry with the unary - operator, or does it find some practical use in C++ code?

Searching h

Answer 1

Since for arithmetic variables operator+ generates a new value. I use it to generate value copies of reference-like (proxy) types.

template<class T> class ref_of{
   T* impl_; // or a more complicated implementation
public:
   T operator+() const{return *impl_;}
   operator T&()&{return *impl_;}
}

Another option is to use operator* but then the ref_of can be confused with a pointer-like object.

Answer 2

If you explicitly stay clear of any number value semantics for a class, any operator overloading is clear not to "do as the ints do". In that case, the unary plus may get any meaning, doing much more than just returning *this

Prominent example: Boost.Spirit's unary plus for the embedded EBNF's Kleene Plus generates a parser rule that lets it's argument (a parser rule as well) match one or more times.

Answer 3

char ch = 'a';
std::cout << ch << '\n';
std::cout << +ch << '\n';

The first insertion writes the character a to cout. The second insertion writes the numeric value of ch to cout. But that's a bit obscure; it relies on the compiler applying integral promotions for the + operator.