Add more string benchmarks

benchmark/single-source/StringEdits.swift

@@ -0,0 +1,72 @@
+//===--- StringEdits.swift-------------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===----------------------------------------------------------------------===//
+
+import TestsUtils
+import Darwin
+
+var editWords: [String] = [
+  "woodshed",
+  "lakism",
+  "gastroperiodynia",
+]
+
+// FIXME: remove when String is a Collection
+extension String: RangeReplaceableCollection { }
+
+let alphabet = "abcdefghijklmnopqrstuvwxyz"
+/// All edits that are one edit away from `word`
+func edits(_ word: String) -> Set<String> {
+  // create right/left splits as CharacterViews instead
+  let splits = word.characters.indices.map {
+    (word.characters[word.characters.startIndex..<$0],word.characters[$0..<word.characters.endIndex])
+  }
+  
+  // though it should be, CharacterView isn't hashable
+  // so using an array for now, ignore that aspect...
+  var result: [String.CharacterView] = []
+  
+  for (left,right) in splits {
+    // drop a character
+    result.append(left + right.dropFirst())
+    
+    // transpose two characters
+    if let fst = right.first {
+      let drop1 = right.dropFirst()
+      if let snd = drop1.first {
+        result.append(left + [snd,fst] + drop1.dropFirst())
+      }
+    }
+    
+    // replace each character with another
+    for letter in alphabet {
+      result.append(left + [letter] + right.dropFirst())
+    }
+    
+    // insert rogue characters
+    for letter in alphabet {
+      result.append(left + [letter] + right)
+    }
+  }
+  
+  // have to map back to strings right at the end
+  return Set(result.lazy.map(String.init))
+}
+
+@inline(never)
+public func run_StringEdits(_ N: Int) {
+  for _ in 1...N*100 {
+    for word in editWords {
+      _ = edits(word)      
+    }
+  }
+}
+