Re: Automatially move from $n (was: C++11 move semantics)

[Hans Åberg]

> On 1 Apr 2018, at 21:47, Frank Heckenbach <address@hidden> wrote:
> 
> Hans Åberg wrote:
> 
>>>> Maybe Bison might support some additional symbol for move action values, 
>>>> like $$k.
>>> 
>>> I'd thought about this, but it would require changes to Bison itself
>>> (for a rather special feature, only for only target language, which
>>> can be done in the skeletons), and the user grammar files would also
>>> look differently, whereas with my way, they generally look just like
>>> they would with shared pointers, or in C, Java, etc., i.e.
>>> "$$ = make_foo ($1, $2)".
>>> 
>>> Also "$$k" would look rather similar to "$$" (probably not strictly
>>> a conflict, but maybe confusing).
>> 
>> Maybe just add to %code:
>>  semantic_type&& operator*(semantic_type& x) { return std::move(x); }
>> and use *$k, in case this operator is not needed for something else.

Should have been inlined:
  inline semantic_type&& operator*(semantic_type& x) { return std::move(x); }

> If semantic_type doesn't have a "*" operator of its own, this might
> work (but look confusing). However, I use the variant (so I'd need
> this function for each alternative, which might be possible to do
> with templates), but some of my semantic values are (smart)
> pointers, so "*" is already used (and even if I could somehow
> override it, it would suggest dereferencing rather than moving).

Alternative unary operators are listed as point 3 at [1]. One can overload 
operator&, but is more confusing than *, as it disables taking the address-of.

1. http://en.cppreference.com/w/cpp/language/operator_precedence

> Now, if C++ had a dedicated move operator (which would also be
> useful in other code) ... But (ab)using an existing operator seems
> confusing to me.

Or a shorter name.