> int[] a = [0]; > auto b = a; > a ~= 1; > b ~= 2; > What is a[1]? > > Is this considered "stomping" and requiring a re-allocation?
Can this question be answered without the recourse to implementation, and the MRU cache in particular? I thought about an abstract definition of "stomping".Something like that: The expanded part of the array is never implicitly shared with any other array. But I'm not sure about this case: int[] a = [1, 2, 3]; int[] b = a[0..1]; b ~= 4; what is a[1]? By my definition, this would be considered stomping, but I couldn't find this example in TDPL. I'm also not sure what to make of this statement: "client code is guaranteed to benefit of good average performance over a large number of appends to the same array". Since "good" is open to interpretation, such a guarantee is meaningless. If it is meant as "amortized O(1)", it's impossible to fulfill, unless the MRU cache is infinite and a lookup is O(1). Then there is the problem of multithreading. A global MRU cache would require potentially expensive synchronization. A thread-local cache, on the other hand, makes thread creation even more heavy-weight than it is right now. My prediction is that D will be evolving towards user-level threads and fine granularity concurrency, which requires very small thread footprint.
