Add remove(where:) to RangeReplaceableCollection

stdlib/public/core/RangeReplaceableCollection.swift

@@ -353,6 +353,15 @@ public protocol RangeReplaceableCollection : Collection
   /// - Complexity: O(*n*), where *n* is the length of the collection.
   mutating func removeAll(keepingCapacity keepCapacity: Bool /*= false*/)
 
+  /// Removes from the collection all elements that satisfy the given predicate.
+  ///
+  /// - Parameter predicate: A closure that takes an element of the
+  ///   sequence as its argument and returns a Boolean value indicating
+  ///   whether the element should be removed from the collection.
+  ///
+  /// - Complexity: O(*n*), where *n* is the length of the collection.
+  mutating func removeAll(where predicate: (Element) throws -> Bool) rethrows
+
   // FIXME(ABI): Associated type inference requires this.
   subscript(bounds: Index) -> Element { get }
 
@@ -1075,3 +1084,47 @@ extension RangeReplaceableCollection {
     return try Self(self.lazy.filter(isIncluded))
   }
 }
+
+extension RangeReplaceableCollection where Self: MutableCollection {
+  /// Removes from the collection all elements that satisfy the given predicate.
+  ///
+  /// - Parameter predicate: A closure that takes an element of the
+  ///   sequence as its argument and returns a Boolean value indicating
+  ///   whether the element should be removed from the collection.
+  ///
+  /// - Complexity: O(*n*), where *n* is the length of the collection.
+  @_inlineable
+  public mutating func removeAll(
+    where predicate: (Element) throws -> Bool
+  ) rethrows {
+    if var i = try index(where: predicate) {
+      var j = index(after: i)
+      while j != endIndex {
+        if try !predicate(self[j]) {
+          swapAt(i, j)
+          formIndex(after: &i)
+        }
+        formIndex(after: &j)
+      }
+      removeSubrange(i...)
+    }
+  }
+}
+
+extension RangeReplaceableCollection {
+  /// Removes from the collection all elements that satisfy the given predicate.
+  ///
+  /// - Parameter predicate: A closure that takes an element of the
+  ///   sequence as its argument and returns a Boolean value indicating
+  ///   whether the element should be removed from the collection.
+  ///
+  /// - Complexity: O(*n*), where *n* is the length of the collection.
+  @_inlineable
+  public mutating func removeAll(
+    where predicate: (Element) throws -> Bool
+  ) rethrows {
+    // FIXME: Switch to using RRC.filter once stdlib is compiled for 4.0
+    // self = try filter { try !predicate($0) }
+    self = try Self(self.lazy.filter { try !predicate($0) })
+  }
+}

test/stdlib/RemoveElements.swift

@@ -0,0 +1,107 @@
+//===--- RemoveElements.swift - tests for lazy filtering-------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+// RUN: %target-run-simple-swift
+// REQUIRES: executable_test
+
+import StdlibUnittest
+
+
+let RemoveElements = TestSuite("RemoveElements")
+
+extension RangeReplaceableCollection where Element: Equatable {
+  mutating func remove(equalTo: Element) {
+    removeAll(where: { $0 == equalTo })
+  }
+}
+
+RemoveElements.test("removing-array-with-predicate") {
+  var a = Array(0..<10)
+  a.removeAll(where: { $0 % 2 == 0 })
+  expectEqualSequence([1,3,5,7,9], a)
+}
+
+RemoveElements.test("removing-array-nothing") {
+  var a = Array(0..<5)
+  a.removeAll(where: { _ in false })
+  expectEqualSequence(0..<5, a)
+}
+
+RemoveElements.test("removing-array-everything") {
+  var a = Array(0..<5)
+  a.removeAll(where: { _ in true })
+  expectEqualSequence([], a)
+}
+
+RemoveElements.test("removing-array-from-empty") {
+  var a: [Int] = []
+  a.removeAll(where: { _ in true })
+  expectEqualSequence([], a)
+}
+
+RemoveElements.test("removing-array-with-equatable") {
+  var a = Array(0..<5)
+  a.remove(equalTo: 6)
+  expectEqualSequence([0,1,2,3,4], a)
+  a.remove(equalTo: 3)
+  expectEqualSequence([0,1,2,4], a)
+  a.remove(equalTo: 0)
+  expectEqualSequence([1,2,4], a)
+  a.remove(equalTo: 4)
+  expectEqualSequence([1,2], a)
+  a.remove(equalTo: 1)
+  expectEqualSequence([2], a)
+  a.remove(equalTo: 2)
+  expectEqualSequence([], a)
+}
+
+RemoveElements.test("removing-string-with-predicate") {
+  var s = "0123456789"
+  s.removeAll(where: { Int(String($0))! % 2 == 0 })
+  expectEqualSequence("13579", s)
+}
+
+RemoveElements.test("removing-string-nothing") {
+  var s = "01234"
+  s.removeAll(where: { _ in false })
+  expectEqualSequence("01234", s)
+}
+
+RemoveElements.test("removing-string-everything") {
+  var s =  "01234"
+  s.removeAll(where: { _ in true })
+  expectEqualSequence("", s)
+}
+
+RemoveElements.test("removing-string-from-empty") {
+  var s = ""
+  s.removeAll(where: { _ in true })
+  expectEqualSequence("", s)
+}
+
+RemoveElements.test("removing-string-with-equatable") {
+  var s = "01234"
+  s.remove(equalTo: "6")
+  expectEqualSequence("01234", s)
+  s.remove(equalTo: "3")
+  expectEqualSequence("0124", s)
+  s.remove(equalTo: "0")
+  expectEqualSequence("124", s)
+  s.remove(equalTo: "4")
+  expectEqualSequence("12", s)
+  s.remove(equalTo: "1")
+  expectEqualSequence("2", s)
+  s.remove(equalTo: "2")
+  expectEqualSequence("", s)
+}
+
+runAllTests()
+