May as well be BidirectionalIndexType

Robert Thompson · Robert Thompson · commit 0598dc1d9105 · 2016-02-18T17:59:35.000-05:00
diff --git a/Treap/TreapCollectionType.swift b/Treap/TreapCollectionType.swift
@@ -62,14 +62,18 @@ extension Treap: CollectionType {
     }
 }
 
-public struct TreapIndex<Key: Comparable>: ForwardIndexType {
+public struct TreapIndex<Key: Comparable>: BidirectionalIndexType {
     private let keys: [Key]
     private let keyIndex: Int
 
     public func successor() -> TreapIndex {
         return TreapIndex(keys: keys, keyIndex: keyIndex + 1)
     }
 
+    public func predecessor() -> TreapIndex {
+        return TreapIndex(keys: keys, keyIndex: keyIndex - 1)
+    }
+
     private init(keys: [Key] = [], keyIndex: Int = 0) {
         self.keys = keys
         self.keyIndex = keyIndex

Original file line number	Diff line number	Diff line change
`@@ -62,14 +62,18 @@ extension Treap: CollectionType {`
`62`	`62`	`}`
`63`	`63`	`}`
`64`	`64`
`65`		`-public struct TreapIndex<Key: Comparable>: ForwardIndexType {`
	`65`	`+public struct TreapIndex<Key: Comparable>: BidirectionalIndexType {`
`66`	`66`	`private let keys: [Key]`
`67`	`67`	`private let keyIndex: Int`
`68`	`68`
`69`	`69`	`public func successor() -> TreapIndex {`
`70`	`70`	`return TreapIndex(keys: keys, keyIndex: keyIndex + 1)`
`71`	`71`	`}`
`72`	`72`
	`73`	`+ public func predecessor() -> TreapIndex {`
	`74`	`+ return TreapIndex(keys: keys, keyIndex: keyIndex - 1)`
	`75`	`+ }`
	`76`	`+`
`73`	`77`	`private init(keys: [Key] = [], keyIndex: Int = 0) {`
`74`	`78`	`self.keys = keys`
`75`	`79`	`self.keyIndex = keyIndex`