Setting array length to 0 discards reserved allocation?

[Jonathan M Davis via Digitalmars-d]

On Wednesday, 30 July 2014 at 06:11:58 UTC, Dominikus Dittes 
Scherkl wrote:
> On Wednesday, 30 July 2014 at 05:55:58 UTC, Jonathan M Davis 
> wrote:
>> I'm completely opposed to changing the official terminology.
> Why?
>
> What buys it, to have two terms "slice" and "dynamic array" if 
> they mean exactly the same thing?
> Especially if we have two different things, the memory and the 
> reference to the memory, but both terms are only adressin the 
> second thing.
> I would prefer to have one term meaning the one thing and the 
> other term meaning the other thing.
> Words are changing meaning over the years, and I think it is 
> very instructive to use "dynamic array" to mean the memory, and 
> "slice" to mean the reference to the memory - as done in the 
> article. May be that was not the original meaning of those 
> terms but it is useful, instructive and unambigous, so it 
> should go in the official terminology. (otherwise we would need 
> a new, third term to describe the "other thing" that is not 
> directly accessible in the current language spec wording - but 
> we have none and it would only increase the confusion).

The "other thing" is just a block of memory managed by the GC and 
which keeps track of the farthest into the block a particular 
slice / dynamic array has grown. It doesn't actually act like a 
dynamic array at all, because it doesn't ever grow. It's just 
used by the GC to provide memory for dynamic arrays and is only 
associated with a particular dynamic array until that array is 
reallocated. Calling that block of memory a dynamic array would 
be like calling the guts of a std::vector a dynamic array instead 
calling std::vector a dynamic array. It's just the memory and 
bookkeeping that backs the dynamic array.

And dynamic array and slice are already not entirely the same, 
because of more general slicing operations. A dynamic array is 
always a slice, but if you're talking about the language in 
general and not arrays specifically, a slice could be something 
else - e.g. you can slice a DList to get a range over it. It's 
less common that those are referred to as slices, but they 
essentially are, and you use opSlice to get them.

I'm increasingly tempted to just write up a new article that uses 
the correct terminology. And if I can do that properly, then 
maybe it'll help clear up the confusion.

- Jonathan M Davis