From slices to perfect imitators: opByValue

[Sönke Ludwig via Digitalmars-d]

Am 08.05.2014 15:57, schrieb monarch_dodra:
> On Thursday, 8 May 2014 at 12:48:17 UTC, Sönke Ludwig wrote:
>> Am 08.05.2014 13:05, schrieb monarch_dodra:
>>> Not necessarily: As soon as indirections come into play, you are
>>> basically screwed, since const is "turtles all the way down".
>>>
>>> So for example, the conversion from "const RefCounted!T" to
>>> "RefCounted!(const T)" is simply not possible, because it strips the
>>> const-ness of the ref count.
>>>
>>> What we would *really* need here is NOT:
>>> "const RefCounted!T" => "RefCounted!(const T)"
>>> But rather
>>> "RefCounted!T" => "RefCounted!(const T)"
>>>
>>> The idea is to cut out the "head const" directly. This also applies to
>>> most ranges too BTW.
>>>
>>> We'd be much better of if we never used `const MyRange!T` to begin with,
>>> but simply had a conversion from `MyRange!T` to `MyRange!(const T)`,
>>> which references the same data.
>>>
>>> In fact, I'm wondering if this might not be a more interesting direction
>>> to explore.
>>
>> The reference count _must_ be handled separate from the payload's
>> const-ness, or a const(RefCount!T) would be completely dysfunctional.
>
> Right, which is my point: "const(RefCount!T)" *is* dysfunctional, which
> is why you'd want to skip it out entirely in the first place.This holds
> true for types implemented with RefCount, such as Array and Array.Range.

Okay, I didn't know that. For various reasons (mostly weak ref support) 
I'm using my own RefCount template, which casts away const-ness of the 
reference counter internally.