[phobos] slice vs. append

[Andrei Alexandrescu]

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