An exegesis of Walter's reference counted slice

[Andrei Alexandrescu via Digitalmars-d]

On 2/25/15 1:58 AM, Ivan Timokhin wrote:
> Oh. So, whenever you pass a reference-counted slice around, you need to do
> it with the full inc/dec protocol, which, as Walter has mentioned several
> times already, leads to code bloat and performance hits. So... no to
> efficient reference counting? Also, no slicing of static arrays in @safe
> code?

Correct.

There's an issue of perception that I just figured, which explains a lot 
of the drama and trash talk about DIP25.

DIP25 is not a borrowing mechanism. Its charter is to make reference 
counted structs (and a variety of other structs) usable in @safe code. 
As RCSlice shows, with DIP25 a reference counted slice switches from 
unusable to usable in @safe code by adding one token to an otherwise 
unchanged implementation. That is Remarkable, and is Good Programming 
Language Design(tm).

Borrowing data in a scoped manner is the charter of DIP69. Given the 
excellent quality of DIP25, it's likely it is Here To Stay and DIP69, or 
any other proposal for borrowing, will work with it (and probably 
leverage it).


Andrei