On 11/14/2015 05:05 PM, Andrei Alexandrescu wrote:
Technically, that clearly works. There's a problem with scaling it up: COMPOSITION ...
Composition matters.
Disallowing immutable(RC!T) in favor of RC!(immutable T) effectively disables composition of larger immutable objects from smaller ones. One obvious thing to do is with a reference counted object it to make it a field of a larger object. That effectively makes that larger object impossible to be used with immutable, transitively. That's not a bad thing; it's merely a factual acknowledgment that in the D programming language, immutable models (transitively and in a way that makes composition possible) true immutability of bits, which makes sharing possible at no cost. Reference counting is mutating, therefore it does not and cannot work with immutability as defined by D.
Obviously. But RC /does/ work with persistent containers! (Unless the author of the container has added a gratuitous compile-time check to make it impossible.)
