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Improve performance of Collection.removeFirst(_:) where Self == SubSequence #32451

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Merged
merged 5 commits into from
Jun 28, 2020
Merged

Improve performance of Collection.removeFirst(_:) where Self == SubSequence #32451

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099ecbe
Improve performance of Collection.removeFirst(_:) where Self == SubSe…
stephencelis Jun 18, 2020
ce78396
Update stdlib/public/core/Collection.swift
stephencelis Jun 18, 2020
0ce01d5
Update Collection.swift
stephencelis Jun 18, 2020
3b8d8b7
Update Collection.swift
stephencelis Jun 18, 2020
e150b37
Others
stephencelis Jun 19, 2020
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8 changes: 5 additions & 3 deletions stdlib/public/core/Collection.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -1664,8 +1664,10 @@ extension Collection where SubSequence == Self {
public mutating func removeFirst(_ k: Int) {
if k == 0 { return }
_precondition(k >= 0, "Number of elements to remove should be non-negative")
_precondition(count >= k,
"Can't remove more items from a collection than it contains")
self = self[index(startIndex, offsetBy: k)..<endIndex]
guard let idx = index(startIndex, offsetBy: k, limitedBy: endIndex) else {
_preconditionFailure(
"Can't remove more items from a collection than it contains")
}
self = self[idx..<endIndex]
}
}
15 changes: 9 additions & 6 deletions stdlib/public/core/RangeReplaceableCollection.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -590,9 +590,10 @@ extension RangeReplaceableCollection {
public mutating func removeFirst(_ k: Int) {
if k == 0 { return }
_precondition(k >= 0, "Number of elements to remove should be non-negative")
_precondition(count >= k,
"Can't remove more items from a collection than it has")
let end = index(startIndex, offsetBy: k)
guard let end = index(startIndex, offsetBy: k, limitedBy: endIndex) else {
_preconditionFailure(
"Can't remove more items from a collection than it has")
}
removeSubrange(startIndex..<end)
}

Expand Down Expand Up @@ -698,9 +699,11 @@ extension RangeReplaceableCollection where SubSequence == Self {
public mutating func removeFirst(_ k: Int) {
if k == 0 { return }
_precondition(k >= 0, "Number of elements to remove should be non-negative")
_precondition(count >= k,
"Can't remove more items from a collection than it contains")
self = self[index(startIndex, offsetBy: k)..<endIndex]
guard let idx = index(startIndex, offsetBy: k, limitedBy: endIndex) else {
_preconditionFailure(
"Can't remove more items from a collection than it contains")
}
self = self[idx..<endIndex]
}
}

Expand Down