From slices to perfect imitators: opByValue

[monarch_dodra via Digitalmars-d]

On Thursday, 8 May 2014 at 07:09:24 UTC, Sönke Ludwig wrote:
> Just a general note: This is not only interesting for 
> range/slice types, but for any user defined reference type 
> (e.g. RefCounted!T or Isolated!T).

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.