[SR-3444] map, filter on RangeReplaceableCollection should return Self
#46,032 建立於 2016年12月17日
描述
| Previous ID | SR-3444 |
| Radar | None |
| Original Reporter | @airspeedswift |
| Type | Improvement |
| Votes | 1 |
| Component/s | Standard Library |
| Labels | Improvement, StarterProposal, swift-evolution-proposal-needed |
| Assignee | None |
| Priority | Medium |
md5: 05669e9e4e1c642618be3a82e1ececb1
Issue Description:
Currently, map and filter on Sequence return an Array, even though the implementation use only capabilities of Array that are available on RangeReplaceableCollection* (an empty init, reserveCapacity, and append).
This means that RangeReplaceableCollection could implement a version of map that returned the same type. For example, a Deque could return another Deque. This is probably what most users would expect for these types.
This would only apply to RRCs that could hold the mapped-to element type. Also note that, in the case of map, this would only apply to transformations that return the same element type – to represent a transformation to another type would require higher-kinder types. And sequences and non-RRC collections, like Set would need to return arrays.
*(this isn't completely true: it creates a ContiguousArray and then turns it into an Array. But hopefully this optimization could be removed at some point)