Add labels to the tuples produced by chunked(on:)
#259
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Label the tuple produced by `chunked(on:)` with `subject` and
`chunk`. This will improve the legibility of code downstream of
the said function. For example, when providing an identifier
for SwiftUI's `ForEach`:
```
-ForEach(chunkedByDate, id: \.0) { date, items in
+ForEach(chunkedByDate, id: \.subject) { date, items in
```
This aligns `ChunkedOnCollection` with the `IndexedCollection`,
which specifies `index` and `element` as well as the built-in
`EnumeratedSequence` (specifying `offset` and `element`).
The introduction of the label will have no effect on existing code,
because the index-based address of the tuple component will remain
unchanged and absent labels will be inferred.
|
Aside: Ruby’s analogue, |
cweider
commented
Aug 8, 2025
| let lazyChunks = fruits.lazy.chunked(on: { $0.first }) | ||
| XCTAssert(lazyChunks.first!.0 == lazyChunks.first!.subject) | ||
| XCTAssert(lazyChunks.first!.1 == lazyChunks.first!.chunk) | ||
| } |
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Test is a bit artificial – correctness is known statically. The best justification is that inhibits subsequent change to the labels. I welcome your thoughts here.
cweider
commented
Aug 8, 2025
| @@ -509,7 +510,7 @@ extension Collection { | |||
| @inlinable | |||
| public func chunked<Subject: Equatable>( | |||
| on projection: (Element) throws -> Subject | |||
| ) rethrows -> [(Subject, SubSequence)] { | |||
| ) rethrows -> [ChunkedOnCollection<Self, Subject>.Element] { | |||
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The implementation below sidesteps ChunkedOnCollection, but aliasing seems sensible given Array-ness is the only material difference between this and the LazySequenceProtocol function.
cweider
commented
Aug 8, 2025
| @@ -162,6 +162,7 @@ public struct ChunkedOnCollection<Base: Collection, Subject: Equatable> { | |||
|
|
|||
| extension ChunkedOnCollection: Collection { | |||
| public typealias Index = ChunkedByCollection<Base, Subject>.Index | |||
| public typealias Element = (subject: Subject, chunk: Base.SubSequence) | |||
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cf. IndexedCollection:
swift-algorithms/Sources/Algorithms/Indexed.swift
Lines 25 to 27 in 0b70cac
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Label the tuple produced by
chunked(on:)(see #142) withsubjectandchunk. This alignsChunkedOnCollectionwith theIndexedCollection, which specifiesindexandelementas well as the built-inEnumeratedSequence(specifyingoffsetandelement).This will also improve the legibility of code downstream of the said function. For example, when providing an identifier for SwiftUI's
ForEach:The introduction of the label will have no effect on existing code, because the index-based address of the tuple component will remain unchanged and absent labels will be inferred. This said, the label choice should be considered carefully since subsequent relabelings will disrupt established code.
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