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Fix Insertion Indices #7

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merged 9 commits into from
Jan 5, 2016
Merged

Fix Insertion Indices #7

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50cf7bb
Minor: fix white space
Jan 5, 2016
b0d8a56
Use indices into target for insertions and substitutions
Jan 5, 2016
db48df7
Add tests to verify indices of deletions, insertions
Jan 5, 2016
4199870
Add tests from @davedelong tweet
Jan 5, 2016
e565c01
Add test from Apple's UITableView documentation
Jan 5, 2016
06af0cd
Add tests exercising all four operations
Jan 5, 2016
4bd94f9
Update README with more information on indices
Jan 5, 2016
ab23042
Update code to use example from Apple's guide
Jan 5, 2016
18f62cd
Change DeLong link from Twitter to GitHub
Jan 5, 2016
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9 changes: 4 additions & 5 deletions Changeset/Changeset.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -72,7 +72,6 @@ public struct Changeset<T: CollectionType where T.Generator.Element: Equatable,
let m = s.count
let n = t.count


// Fill first row and column of insertions and deletions.

var d: [[[Edit<T.Generator.Element>]]] = Array(count: m + 1, repeatedValue: Array(count: n + 1, repeatedValue: []))
Expand All @@ -93,12 +92,12 @@ public struct Changeset<T: CollectionType where T.Generator.Element: Equatable,

guard m > 0 && n > 0 else { return d[m][n] }

// Fill body of matrix.

// Indexes into the two collections.
var sx: T.Index
var tx = t.startIndex

// Fill body of matrix.

for j in 1...n {
sx = s.startIndex

Expand All @@ -119,11 +118,11 @@ public struct Changeset<T: CollectionType where T.Generator.Element: Equatable,
del.append(deletion)
d[i][j] = del
} else if ins.count == minimumCount {
let insertion = Edit(.Insertion, value: t[tx], destination: i)
let insertion = Edit(.Insertion, value: t[tx], destination: j - 1)
ins.append(insertion)
d[i][j] = ins
} else {
let substitution = Edit(.Substitution, value: t[tx], destination: i - 1)
let substitution = Edit(.Substitution, value: t[tx], destination: j - 1)
sub.append(substitution)
d[i][j] = sub
}
Expand Down
175 changes: 150 additions & 25 deletions ChangesetTests/ChangesetTests.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -45,21 +45,21 @@ class ChangesetTests: XCTestCase {
edits = [
Edit(.Deletion, value: "a", destination: 1),
Edit(.Deletion, value: "t", destination: 2),
Edit(.Substitution, value: "n", destination: 4),
Edit(.Substitution, value: "n", destination: 2),
]
XCTAssertEqual(changeset.edits, edits)

changeset = Changeset(source: "Sunday".characters, target: "Saturday".characters)
edits = [
Edit(.Insertion, value: "a", destination: 1),
Edit(.Insertion, value: "t", destination: 1),
Edit(.Substitution, value: "r", destination: 2),
Edit(.Insertion, value: "t", destination: 2),
Edit(.Substitution, value: "r", destination: 4),
]
XCTAssertEqual(changeset.edits, edits)

changeset = Changeset(source: "sword".characters, target: "words".characters)
edits = [
Edit(.Move(origin: 0), value: "s", destination: 5),
Edit(.Move(origin: 0), value: "s", destination: 4),
]
XCTAssertEqual(changeset.edits, edits)

Expand All @@ -78,27 +78,152 @@ class ChangesetTests: XCTestCase {
]
XCTAssertEqual(changeset.edits, edits)

changeset = Changeset(source: "ABCD".characters, target: "abcd".characters)
edits = [
Edit(.Substitution, value: "a", destination: 0),
Edit(.Substitution, value: "b", destination: 1),
Edit(.Substitution, value: "c", destination: 2),
Edit(.Substitution, value: "d", destination: 3),
]
XCTAssertEqual(changeset.edits, edits)

// GARVEY -> AVERY (http://stackoverflow.com/a/30795531)
changeset = Changeset(source: "GARVEY".characters, target: "AVERY".characters)
edits = [
Edit(.Deletion, value: "G", destination: 0),
Edit(.Move(origin: 2), value: "R", destination: 5),
Edit(.Move(origin: 2), value: "R", destination: 3),
]
XCTAssertEqual(changeset.edits, edits)

changeset = Changeset(source: "AVERY".characters, target: "GARVEY".characters)
edits = [
Edit(.Insertion, value: "G", destination: 0),
Edit(.Move(origin: 3), value: "R", destination: 1),
Edit(.Move(origin: 3), value: "R", destination: 2),
]
XCTAssertEqual(changeset.edits, edits)
}

func testInsertionsAfterDeletions() {

var changeset: Changeset<String.CharacterView>
var edits: Array<Edit<String.CharacterView.Generator.Element>>

changeset = Changeset(source: "abcdefgh".characters, target: "bdefijgh".characters)
edits = [
Edit(.Deletion, value: "a", destination: 0),
Edit(.Deletion, value: "c", destination: 2),
Edit(.Insertion, value: "i", destination: 4),
Edit(.Insertion, value: "j", destination: 5),
]
XCTAssertEqual(changeset.edits, edits)

changeset = Changeset(source: "bdefijgh".characters, target: "abcdefgh".characters)
edits = [
Edit(.Insertion, value: "a", destination: 0),
Edit(.Insertion, value: "c", destination: 2),
Edit(.Deletion, value: "i", destination: 4),
Edit(.Deletion, value: "j", destination: 5),
]
XCTAssertEqual(changeset.edits, edits)

changeset = Changeset(source: "abcdefgh".characters, target: "bdefagch".characters)
edits = [
Edit(.Move(origin: 0), value: "a", destination: 4),
Edit(.Move(origin: 2), value: "c", destination: 6),
]
XCTAssertEqual(changeset.edits, edits)

changeset = Changeset(source: "bdefagch".characters, target: "abcdefgh".characters)
edits = [
Edit(.Move(origin: 4), value: "a", destination: 0),
Edit(.Move(origin: 6), value: "c", destination: 2),
]
XCTAssertEqual(changeset.edits, edits)
}

func testComplexChange() {

var changeset: Changeset<String.CharacterView>
var edits: Array<Edit<String.CharacterView.Generator.Element>>

changeset = Changeset(source: "abcdefgh".characters, target: "bacefxhi".characters)
edits = [
Edit(.Move(origin: 1), value: "b", destination: 0),
Edit(.Deletion, value: "d", destination: 3),
Edit(.Substitution, value: "x", destination: 5),
Edit(.Insertion, value: "i", destination: 7),
]
XCTAssertEqual(changeset.edits, edits)

changeset = Changeset(source: "bacefxhi".characters, target: "abcdefgh".characters)
edits = [
Edit(.Move(origin: 1), value: "a", destination: 0),
Edit(.Insertion, value: "d", destination: 3),
Edit(.Substitution, value: "g", destination: 6),
Edit(.Deletion, value: "i", destination: 7),
]
XCTAssertEqual(changeset.edits, edits)
}

func testListing7_8() {

// https://developer.apple.com/library/ios/documentation/UserExperience/Conceptual/TableView_iPhone/ManageInsertDeleteRow/ManageInsertDeleteRow.html#//apple_ref/doc/uid/TP40007451-CH10-SW16

let changeset: Changeset<Array<String>>
let edits: Array<Edit<String>>

let source = ["Arizona", "California", "Delaware", "New Jersey", "Washington"]
let target = ["Alaska", "Arizona", "California", "Georgia", "New Jersey", "Virginia"]

/* In Apple's example the changeset consists of these five changes:
Edit(.Insertion, value: "Alaska", destination: 0),
Edit(.Deletion, value: "Delaware", destination: 2),
Edit(.Insertion, value: "Georgia", destination: 3),
Edit(.Deletion, value: "Washington", destination: 4),
Edit(.Insertion, value: "Virginia", destination: 5),
Changeset reduces this to the following three:*/

changeset = Changeset(source: source, target: target)
edits = [
Edit(.Insertion, value: "Alaska", destination: 0),
Edit(.Substitution, value: "Georgia", destination: 3),
Edit(.Substitution, value: "Virginia", destination: 5),
]
XCTAssertEqual(changeset.edits, edits)
}

func testDeLongTweet() {

// https://twitter.com/davedelong/status/671051521371406336

var changeset: Changeset<String.CharacterView>
var edits: Array<Edit<String.CharacterView.Generator.Element>>

changeset = Changeset(source: "words".characters, target: "tsword".characters)
edits = [
Edit(.Insertion, value: "t", destination: 0),
Edit(.Move(origin: 4), value: "s", destination: 1),
]
XCTAssertEqual(changeset.edits, edits)

changeset = Changeset(source: "abcdefgh".characters, target: "agbcdefh".characters)
edits = [
Edit(.Move(origin: 6), value: "g", destination: 1),
]
XCTAssertEqual(changeset.edits, edits)

changeset = Changeset(source: "stick".characters, target: "tact".characters)
edits = [
Edit(.Deletion, value: "s", destination: 0),
Edit(.Substitution, value: "a", destination: 1),
Edit(.Substitution, value: "t", destination: 3),
]
XCTAssertEqual(changeset.edits, edits)

changeset = Changeset(source: "12345".characters, target: "2a3".characters)
edits = [
Edit(.Deletion, value: "1", destination: 0),
Edit(.Insertion, value: "a", destination: 1),
Edit(.Deletion, value: "4", destination: 3),
Edit(.Deletion, value: "5", destination: 4),
]
XCTAssertEqual(changeset.edits, edits)

changeset = Changeset(source: "dave".characters, target: "david".characters)
edits = [
Edit(.Substitution, value: "i", destination: 3),
Edit(.Insertion, value: "d", destination: 4),
]
XCTAssertEqual(changeset.edits, edits)
}
Expand Down Expand Up @@ -164,18 +289,18 @@ class ChangesetTests: XCTestCase {
changeset = Changeset(source: "a".characters, target: "bac".characters)
edits = [
Edit(.Insertion, value: "b", destination: 0),
Edit(.Insertion, value: "c", destination: 1),
Edit(.Insertion, value: "c", destination: 2),
]
XCTAssertEqual(changeset.edits, edits)

changeset = Changeset(source: "abcdef".characters, target: "aAbBcCdDeEfF".characters)
edits = [
Edit(.Insertion, value: "A", destination: 1),
Edit(.Insertion, value: "B", destination: 2),
Edit(.Insertion, value: "C", destination: 3),
Edit(.Insertion, value: "D", destination: 4),
Edit(.Insertion, value: "E", destination: 5),
Edit(.Insertion, value: "F", destination: 6),
Edit(.Insertion, value: "B", destination: 3),
Edit(.Insertion, value: "C", destination: 5),
Edit(.Insertion, value: "D", destination: 7),
Edit(.Insertion, value: "E", destination: 9),
Edit(.Insertion, value: "F", destination: 11),
]
XCTAssertEqual(changeset.edits, edits)
}
Expand All @@ -196,15 +321,15 @@ class ChangesetTests: XCTestCase {

changeset = Changeset(source: "abbcdefgh".characters, target: "acdefgbbh".characters)
edits = [
Edit(.Move(origin: 1), value: "b", destination: 8),
Edit(.Move(origin: 2), value: "b", destination: 8),
Edit(.Move(origin: 1), value: "b", destination: 6),
Edit(.Move(origin: 2), value: "b", destination: 7),
]
XCTAssertEqual(changeset.edits, edits)

changeset = Changeset(source: "acdefgbbh".characters, target: "abbcdefgh".characters)
edits = [
Edit(.Move(origin: 6), value: "b", destination: 1),
Edit(.Move(origin: 7), value: "b", destination: 1),
Edit(.Move(origin: 7), value: "b", destination: 2),
]
XCTAssertEqual(changeset.edits, edits)
}
Expand Down Expand Up @@ -236,7 +361,7 @@ class ChangesetTests: XCTestCase {
let changes = [
Edit(.Deletion, value: NSURL(string: "http://a.b.c")!, destination: 0),
Edit(.Deletion, value: NSURL(string: "http://k.l.m")!, destination: 2),
Edit(.Insertion, value: NSURL(string: "http://h.i.j")!, destination: 4),
Edit(.Insertion, value: NSURL(string: "http://h.i.j")!, destination: 2),
]
XCTAssertEqual(changeset.edits, changes)
}
Expand Down
16 changes: 9 additions & 7 deletions README.md
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Original file line number Diff line number Diff line change
Expand Up @@ -2,7 +2,7 @@

A `Changeset` describes the minimal edits required to go from one `CollectionType` of `Equatable` elements to another. It detects additions, deletions, substitutions, and moves.

This is an attempt at implementing the solution outlined in [Dave DeLong](https://twitter.com/davedelong)’s article, [Edit distance and edit steps](http://davedelong.tumblr.com/post/134367865668/edit-distance-and-edit-steps).
This is an attempt at implementing the solution outlined in [Dave DeLong](https://github.com/davedelong)’s article, [Edit distance and edit steps](http://davedelong.tumblr.com/post/134367865668/edit-distance-and-edit-steps).

## Usage

Expand All @@ -29,19 +29,21 @@ let edits = [
assert(changeset.edits == edits)
```

Note that the indexes are into the original source collection.
Because `Changeset` works on any `CollectionType` of `Equatable`, it has many applications. For example, it could be used to identify the changes needed to go from one array of elements to another, where the elements are instances of a custom `Equatable` class. This is particularly useful if these elements are displayed in a `UITableView`, and you want to animate a transition between two sets of data.

Because `Changeset` works on any `CollectionType` of `Equatable`, it has many applications. For example, it could be used to identify the changes needed to go from one array of elements to another, where the elements are instances of a custom `Equatable` class.
Note, indices are those exactly to be used within a `beginUpdates`/`endUpdates` block on `UITableView`.

This is particularly useful if these elements are displayed in a `UITableView` and you want to animate a transition between two sets of data.
In short; first all deletions are made relative to the source collection, then, relative to the resulting collection, insertions and substitutions. A move is just a deletion followed by an insertion on the resulting collection. This is explained in much more detail under [_Batch Insertion, Deletion, and Reloading of Rows and Sections_](https://developer.apple.com/library/ios/documentation/UserExperience/Conceptual/TableView_iPhone/ManageInsertDeleteRow/ManageInsertDeleteRow.html#//apple_ref/doc/uid/TP40007451-CH10-SW9) in Apple’s [Table View Programming Guide for iOS](https://developer.apple.com/library/ios/documentation/UserExperience/Conceptual/TableView_iPhone/AboutTableViewsiPhone/AboutTableViewsiPhone.html).

If you don’t want the overhead of the `Changeset`, which stores the source and target collections, you can call `editDistance` directly:
If you don’t want the overhead of `Changeset` itself, which also stores the source and target collections, you can call `editDistance` directly (here with [example data](https://developer.apple.com/library/ios/documentation/UserExperience/Conceptual/TableView_iPhone/ManageInsertDeleteRow/ManageInsertDeleteRow.html#//apple_ref/doc/uid/TP40007451-CH10-SW16)) from Apple’s guide:

```swift
let edits = Changeset.editDistance(source: "kitten".characters, target: "sitting".characters)
let source = ["Arizona", "California", "Delaware", "New Jersey", "Washington"]
let target = ["Alaska", "Arizona", "California", "Georgia", "New Jersey", "Virginia"]
let edits = Changeset.editDistance(source: source, target: target)

print(edits)
// [replace with s at index 0, replace with i at index 4, insert g at index 6]
// [insert Alaska at index 0, replace with Georgia at index 3, replace with Virginia at index 5]
```

## License
Expand Down