Skip to content

[stdlib] Revise collection difference documentation #24675

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
merged 2 commits into from
May 10, 2019
Merged

[stdlib] Revise collection difference documentation #24675

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
71439a2
Revise CollectionDifference documentation.
natecook1000 Apr 25, 2019
42d36f9
Minor revisions.
natecook1000 May 10, 2019
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
57 changes: 33 additions & 24 deletions stdlib/public/core/CollectionDifference.swift
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -10,19 +10,26 @@
//
//===----------------------------------------------------------------------===//

/// A type that represents the difference between two ordered collection states.
/// A collection of insertions and removals that describe the difference
/// between two ordered collection states.
@available(macOS 9999, iOS 9999, tvOS 9999, watchOS 9999, *) // FIXME(availability-5.1)
public struct CollectionDifference<ChangeElement> {
/// A type that represents a single change to a collection.
///
/// The `offset` of each `insert` refers to the offset of its `element` in
/// the final state after the difference is fully applied. The `offset` of
/// each `remove` refers to the offset of its `element` in the original
/// state. Non-`nil` values of `associatedWith` refer to the offset of the
/// complementary change.
/// A single change to a collection.
@_frozen
public enum Change {
/// An insertion.
///
/// The `offset` value is the offset of the inserted element in the final
/// state of the collection after the difference is fully applied.
/// A non-`nil` `associatedWith` value is the offset of the complementary
/// change.
case insert(offset: Int, element: ChangeElement, associatedWith: Int?)

/// A removal.
///
/// The `offset` value is the offset of the element to be removed in the
/// original state of the collection. A non-`nil` `associatedWith` value is
/// the offset of the complementary change.
case remove(offset: Int, element: ChangeElement, associatedWith: Int?)

// Internal common field accessors
Expand Down Expand Up @@ -58,10 +65,11 @@ public struct CollectionDifference<ChangeElement> {
}
}

/// The `.insert` changes contained by this difference, from lowest offset to highest
/// The insertions contained by this difference, from lowest offset to
/// highest.
public let insertions: [Change]

/// The `.remove` changes contained by this difference, from lowest offset to highest
/// The removals contained by this difference, from lowest offset to highest.
public let removals: [Change]

/// The public initializer calls this function to ensure that its parameter
Expand Down Expand Up @@ -117,20 +125,20 @@ public struct CollectionDifference<ChangeElement> {
return removeOffsetToAssoc == insertAssocToOffset
}

/// Creates an instance from a collection of changes.
/// Creates a new collection difference from a collection of changes.
///
/// For clients interested in the difference between two collections, see
/// `BidirectionalCollection.difference(from:)`.
/// To find the difference between two collections, use the
/// `difference(from:)` method declared on the `BidirectionalCollection`
/// protocol.
///
/// To guarantee that instances are unambiguous and safe for compatible base
/// states, this initializer will fail unless its parameter meets to the
/// following requirements:
/// The collection of changes passed as `changes` must meet these
/// requirements:
///
/// 1. All insertion offsets are unique
/// 2. All removal offsets are unique
/// 3. All associations between insertions and removals are symmetric
/// - All insertion offsets are unique
/// - All removal offsets are unique
/// - All associations between insertions and removals are symmetric
///
/// - Parameter c: A collection of changes that represent a transition
/// - Parameter changes: A collection of changes that represent a transition
/// between two states.
///
/// - Complexity: O(*n* * log(*n*)), where *n* is the length of the
Expand Down Expand Up @@ -218,6 +226,7 @@ public struct CollectionDifference<ChangeElement> {
extension CollectionDifference: Collection {
public typealias Element = Change

/// The position of a collection difference.
@_fixed_layout
public struct Index {
// Opaque index type is isomorphic to Int
Expand Down Expand Up @@ -305,12 +314,12 @@ extension CollectionDifference: Hashable where ChangeElement: Hashable {}

@available(macOS 9999, iOS 9999, tvOS 9999, watchOS 9999, *) // FIXME(availability-5.1)
extension CollectionDifference where ChangeElement: Hashable {
/// Infers which `ChangeElement`s have been both inserted and removed only
/// once and returns a new difference with those associations.
/// Returns a new collection difference with associations between individual
/// elements that have been removed and inserted only once.
///
/// - Returns: an instance with all possible moves inferred.
/// - Returns: An collection difference with all possible moves inferred.
///
/// - Complexity: O(*n*) where *n* is `self.count`
/// - Complexity: O(*n*) where *n* is the number of collection differences.
public func inferringMoves() -> CollectionDifference<ChangeElement> {
let uniqueRemovals: [ChangeElement:Int?] = {
var result = [ChangeElement:Int?](minimumCapacity: Swift.min(removals.count, insertions.count))
Expand Down
42 changes: 21 additions & 21 deletions stdlib/public/core/Diffing.swift
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -54,7 +54,7 @@ extension CollectionDifference {
}

extension RangeReplaceableCollection {
/// Applies a difference to a collection.
/// Applies the given difference to this collection.
///
/// - Parameter difference: The difference to be applied.
///
Expand Down Expand Up @@ -112,23 +112,24 @@ extension RangeReplaceableCollection {
// MARK: Definition of API

extension BidirectionalCollection {
/// Returns the difference needed to produce the receiver's state from the
/// parameter's state, using the provided closure to establish equivalence
/// between elements.
/// Returns the difference needed to produce this collection's ordered
/// elements from the given collection, using the given predicate as an
/// equivalence test.
///
/// This function does not infer moves.
/// This function does not infer element moves. If you need to infer moves,
/// call the `inferringMoves()` method on the resulting difference.
///
/// - Parameters:
/// - other: The base state.
/// - areEquivalent: A closure that returns whether the two
/// parameters are equivalent.
/// - areEquivalent: A closure that returns a Boolean value indicating
/// whether two elements are equivalent.
///
/// - Returns: The difference needed to produce the reciever's state from
/// the parameter's state.
///
/// - Complexity: For pathological inputs, worst case performance is
/// O(`self.count` * `other.count`). Faster execution can be expected
/// when the collections share many common elements.
/// - Complexity: Worst case performance is O(*n* * *m*), where *n* is the
/// count of this collection and *m* is `other.count`. You can expect
/// faster execution when the collections share many common elements.
@available(macOS 9999, iOS 9999, tvOS 9999, watchOS 9999, *) // FIXME(availability-5.1)
public func difference<C: BidirectionalCollection>(
from other: C,
Expand Down Expand Up @@ -167,23 +168,22 @@ extension BidirectionalCollection {
}

extension BidirectionalCollection where Element : Equatable {
/// Returns the difference needed to produce the receiver's state from the
/// parameter's state, using equality to establish equivalence between
/// elements.
/// Returns the difference needed to produce this collection's ordered
/// elements from the given collection.
///
/// This function does not infer element moves, but they can be computed
/// using `CollectionDifference.inferringMoves()` if desired.
/// This function does not infer element moves. If you need to infer moves,
/// call the `inferringMoves()` method on the resulting difference.
///
/// - Parameters:
/// - other: The base state.
///
/// - Returns: The difference needed to produce the reciever's state from
/// the parameter's state.
/// - Returns: The difference needed to produce this collection's ordered
/// elements from the given collection.
///
/// - Complexity: For pathological inputs, worst case performance is
/// O(`self.count` * `other.count`). Faster execution can be expected
/// when the collections share many common elements, or if `Element`
/// also conforms to `Hashable`.
/// - Complexity: Worst case performance is O(*n* * *m*), where *n* is the
/// count of this collection and *m* is `other.count`. You can expect
/// faster execution when the collections share many common elements, or
/// if `Element` conforms to `Hashable`.
@available(macOS 9999, iOS 9999, tvOS 9999, watchOS 9999, *) // FIXME(availability-5.1)
public func difference<C: BidirectionalCollection>(
from other: C
Expand Down