dynamic array .length vs .reserve - what's the difference?

[wjoe]

On Saturday, 1 August 2020 at 16:04:01 UTC, Steven Schveighoffer 
wrote:
> On 7/31/20 12:32 PM, wjoe wrote:
>> On Friday, 31 July 2020 at 04:28:57 UTC, Ali Çehreli wrote:
>>> Another option, which is curiously said to be more performant 
>>> in memory allocation than native arrays, is 
>>> std.array.Appender. I've used function-local static Appenders 
>>> to cut down on memory allocation. Here is an uncompiled 
>>> pseudo code:
>>>
>>> [...]
>> 
>> This looks like an even better way to do it.
>> 
>> Thanks, Ali :)
>
> Just FYI, the reason this is faster is because there is no need 
> to go through the opaque calls into druntime to figure out if 
> appending-in-place is possible. The reserved length is stored 
> directly in the struct.
>
> -Steve

That's good to know, thanks :)
By the looks of it, Appender is half duplicating the runtime :)