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 here, I came across What is the purpose of the unary '+' operator in C?, but the only useful scenarios there involve preprocessor macros. Those are good to know, but they seem to be some less common situations, and involve macros. Are there any use cases involving more common C++ code?

Answer 1

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.

Answer 2

Symmetry with unary - isn't entirely useless; it can be used for emphasis:

const int foo = -1; const int bar = +1; 

And an overloaded unary + can be used to denote an operation that yields the same logical value as its operand, while performing some non-trivial computation. (I've seen this done for type conversions in Ada, which permits unary +, but not conversions, to be overloaded.) I don't have a good C++ example to hand, and one could argue that it would be poor style. (Then again, I've seen plenty of rants about overloading <<.)

As for why C++ has it, it's probably largely for consistency with C, which added it with the 1989 ANSI standard. The C Rationale just says:

Unary plus was adopted by the C89 Committee from several implementations, for symmetry with unary minus.