> On Aug 1, 2017, at 3:21 AM, Tino Heth <2...@gmx.de> wrote: > >> FSAs intentionally don’t conform to Collection, because multi-dimensional >> arrays shouldn’t have to conform to a linear (by nature, hence the name >> “Sequence”) standard, at least by default. > I strongly oppose and think it is a really bad idea: > Even if arrays are modelled multi-dimensional, there's always a canonical way > to iterate through their elements, and this is an essential feature of this > data type.
But linear access isn’t an inherent canonical property of multi-dimensional arrays, it’s just a consequence of arrays taking a contiguous block of memory (which is generally treated as linear in computers). Speaking of which, the “withUnsafe(Mutable)Flattening” functions give Collection access. (And it serves as an equivalent to the “T[]” function parameter interface from C.) I was going to support Collection for one-dimensional arrays, but I realized that would be a bad idea since that’s the dimensionality that would exploit vector-unit types the most. So you must convert first. (Well, the “conversion” to an Unsafe(Mutable)BufferPointer should just type-pun the address, unless the array was not initially in conventional addressable memory, which (small) objects aren’t by default in Swift, hence the “Unsafe” part of Swift’s pointer interface.) > Do you have any example for an existing optimisation that is important enough > to cripple all fixed size arrays? > Those would not only be used to represent pixel buffers on a graphics card… Sequence/Collection have other problems fitting with fixed-size arrays. There needs to be a new set of more basic protocols that both arrays and Sequence or Collection can conform to. > Also, if FSA have only one dimension (that's still my preference), all those > issues are can be solved easily in the multidimensional structure build on > top of the array. Or to flip it, just use multi-dimensional arrays with one bound. Multi-dimensionality does not impose an implementation penalty, especially when declaring a one-dimensional array. Wrapping multi-dimensionality in a type would forfeit it being a compound type, which would forfeit piecemeal initialization. There’s no need for Swift arrays to be limited to C arrays plus Assignability (or be just C arrays plus Assignability plus Collection). — Daryle Walker Mac, Internet, and Video Game Junkie darylew AT mac DOT com
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