[stdlib] Add Character.unicodeScalars

stdlib/public/core/CMakeLists.txt

@@ -35,6 +35,7 @@ set(SWIFTLIB_ESSENTIAL
   Builtin.swift
   BuiltinMath.swift.gyb
   Character.swift
+  CharacterUnicodeScalars.swift
   CocoaArray.swift
   Codable.swift
   Collection.swift

stdlib/public/core/Character.swift

@@ -449,4 +449,3 @@ extension Character : Comparable {
     }
   }
 }
-

stdlib/public/core/CharacterUnicodeScalars.swift

@@ -0,0 +1,83 @@
+//===--- CharacterUnicodeScalars.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
+//
+//===----------------------------------------------------------------------===//
+extension Character {
+  public struct UnicodeScalarView {
+    internal let _base: String.UnicodeScalarView
+  }
+
+  public var unicodeScalars : UnicodeScalarView {
+    return UnicodeScalarView(_base: String(self).unicodeScalars)
+  }
+}
+
+extension Character.UnicodeScalarView {
+  public struct Iterator {
+    internal var _base: String.UnicodeScalarView.Iterator
+  }
+}
+
+extension Character.UnicodeScalarView.Iterator : IteratorProtocol {
+  public mutating func next() -> UnicodeScalar? {
+    return _base.next()
+  }
+}
+
+extension Character.UnicodeScalarView : Sequence {
+  public func makeIterator() -> Iterator {
+    return Iterator(_base: _base.makeIterator())
+  }
+}
+
+extension Character.UnicodeScalarView {
+  public struct Index {
+    internal let _base: String.UnicodeScalarView.Index
+  }
+}
+
+extension Character.UnicodeScalarView.Index : Equatable {
+  public static func == (
+    lhs: Character.UnicodeScalarView.Index,
+    rhs: Character.UnicodeScalarView.Index
+  ) -> Bool {
+    return lhs._base == rhs._base
+  }
+}
+
+extension Character.UnicodeScalarView.Index : Comparable {
+  public static func < (
+    lhs: Character.UnicodeScalarView.Index,
+    rhs: Character.UnicodeScalarView.Index
+  ) -> Bool {
+    return lhs._base < rhs._base
+  }
+}
+
+extension Character.UnicodeScalarView : Collection {
+  public var startIndex: Index {
+    return Index(_base: _base.startIndex)
+  }
+  public var endIndex: Index {
+    return Index(_base: _base.endIndex)
+  }
+  public func index(after i: Index) -> Index {
+    return Index(_base: _base.index(after: i._base))
+  }
+  public subscript(_ i: Index) -> UnicodeScalar {
+    return _base[i._base]
+  }
+}
+
+extension Character.UnicodeScalarView : BidirectionalCollection {
+  public func index(before i: Index) -> Index {
+    return Index(_base: _base.index(before: i._base))
+  }
+}

stdlib/public/core/GroupInfo.json

@@ -7,6 +7,7 @@
     "ASCII.swift",
     "CString.swift",
     "Character.swift",
+    "CharacterUnicodeScalars.swift",
     "StaticString.swift",
     "String.swift",
     "StringBridge.swift",

test/stdlib/Character.swift

@@ -219,6 +219,22 @@ func isSmallRepresentation(_ s: String) -> Bool {
   }
 }
 
+func checkUnicodeScalars(_ s: String) {
+  let c = s.first!
+  expectEqualSequence(s.unicodeScalars, c.unicodeScalars)
+
+  expectEqualSequence(
+    s.unicodeScalars, c.unicodeScalars.indices.map { c.unicodeScalars[$0] })
+
+  expectEqualSequence(
+    s.unicodeScalars.reversed(), c.unicodeScalars.reversed())
+
+  expectEqualSequence(
+    s.unicodeScalars.reversed(), c.unicodeScalars.indices.reversed().map {
+      c.unicodeScalars[$0]
+    })
+}
+
 func checkRepresentation(_ s: String) {
   let expectSmall = s.utf8.count <= 8
   let isSmall = isSmallRepresentation(s)
@@ -231,13 +247,15 @@ func checkRepresentation(_ s: String) {
 
 CharacterTests.test("RoundTripping") {
   // Single Unicode Scalar Value tests
-  for s in baseScalars {
-    checkRepresentation(String(s))
-    checkRoundTripThroughCharacter(String(s))
+  for s in baseScalars.lazy.map(String.init) {
+    checkUnicodeScalars(s)
+    checkRepresentation(s)
+    checkRoundTripThroughCharacter(s)
   }
 
   // Edge case tests
   for s in testCharacters {
+    checkUnicodeScalars(s)
     checkRepresentation(s)
     checkRoundTripThroughCharacter(s)
   }
@@ -249,6 +267,7 @@ CharacterTests.test("RoundTripping/Random") {
     // Character's small representation variant has 63 bits. Making
     // the maximum length 9 scalars tests both sides of the limit.
     var s = randomGraphemeCluster(1, 9)
+    checkUnicodeScalars(s)
     checkRepresentation(s)
     checkRoundTripThroughCharacter(s)
   }