Challenge: write a reference counted slice that works as much as possible like a built-in slice

[Atila Neves]

On Tuesday, 9 November 2021 at 15:26:24 UTC, Dukc wrote:
> On Tuesday, 9 November 2021 at 11:56:50 UTC, Atila Neves wrote:
>> I'll hijack this thread with a slide from my DConf Online 2020 
>> talk, because with the current language it's impossible for a 
>> library writer to write a useful @safe vector struct:
>>
>> ```d
>> scope v = vector(1, 2, 3, 4);
>> scope s = v[];
>> v ~= 5;  // could reallocate here
>> s[3] = 42;  // oops
>> ```
>
> Hm, if the vector had a reference count

Then it wouldn't be a vector.

> Functions like these could also solve the thing if only called 
> from `@live`:
>
> ```d
> AppendableVector setupAppending(Vector*);
> Vector stopAppending(AppendableVector*);
> ```
>
> Obviously, you could not slice an AppendableVector, and we're 
> not proposing that average application code should be `@live` 
> so not a very good solution.

The main point of vector is that one can append to it without 
using the GC. I guess that "this thing has a length only known at 
runtime that won't change and doesn't use the GC" is useful too, 
but not nearly as much as being able to append.