[phobos] slice vs. append

[David Simcha]

I personally have written a lot of code that relies on the slice operator
being extremely cheap, which is the whole point of the way D arrays are
designed.  For example, using slicing and tail recursion instead of indices
and looping is a very elegant, readable way of implementing binary search.
I'm not sure we want to add any overhead here, even if it's only a few
instructions.

On Mon, Mar 22, 2010 at 11:04 AM, Andrei Alexandrescu <andrei at erdani.com>wrote:

> Right now array append is reasonably fast due to Steve's great work.
> Basically the append operation caches the capacities of the last arrays that
> were appended to, which makes the capacity query fast most of the time.
>
> I was thinking of a possible change. How about having the slice operator
> arr[a .. b] remove the array from the cache? That way we can handle
> arr.length = n differently:
>
> (a) if n > arr.length, resize appropriately
> (b) if n < arr.length AND the array is in the cache, keep the array in the
> cache.
>
> The change is at (b). If the array is in the cache and its length is made
> smaller, then we can be sure the capacity will stay correct after the
> resizing. This is because we know for sure there will be no stomping - if
> stomping were possible, the array would not be in the cache.
>
> Could this work? And if it does, would it be a good change to make?
>
>
> Andrei
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