swift-mirror/test/1_stdlib/Algorithm.swift.gyb

// -*- swift -*-
// RUN: rm -rf %t ; mkdir -p %t
// RUN: %S/../../utils/gyb %s -o %t/Algorithm.swift
// RUN: %S/../../utils/line-directive %t/Algorithm.swift -- %target-build-swift %t/Algorithm.swift -o %t/a.out
// RUN: %S/../../utils/line-directive %t/Algorithm.swift -- %target-run %t/a.out

import StdlibUnittest
import SwiftPrivate

var Algorithm = TestSuite("Algorithm")

// FIXME(prext): remove this conformance.
extension String.UnicodeScalarView : Equatable {}

// FIXME(prext): remove this function.
public func == (
  lhs: String.UnicodeScalarView, rhs: String.UnicodeScalarView) -> Bool {
  return Array(lhs) == Array(rhs)
}

Algorithm.test("split") {
  expectEqual(
    [ "foo", "  bar baz " ].map { $0.unicodeScalars },
    split("  foo   bar baz ".unicodeScalars, maxSplit: 1) { $0._isSpace() })

  expectEqual(
    [ "foo", "bar", "baz" ].map { $0.unicodeScalars },
    split(
      "  foo   bar baz ".unicodeScalars, allowEmptySlices: false) {
      $0._isSpace()
    })

  expectEqual(
    [ "", "", "foo", "", "", "bar", "baz", "" ].map { $0.unicodeScalars },
    split(
      "  foo   bar baz ".unicodeScalars, allowEmptySlices: true) {
      $0._isSpace()
    })

  expectEqual(
    [ "", "", "foo   bar baz " ].map { $0.unicodeScalars },
    split(
      "  foo   bar baz ".unicodeScalars, allowEmptySlices: true, maxSplit: 2,
      isSeparator: { $0._isSpace() }))
}

// FIXME(prext): move this struct to the point of use.
struct StartsWithTest {
  let expected: Bool
  let sequence: [Int]
  let prefix: [Int]
  let expectedLeftoverSequence: [Int]
  let expectedLeftoverPrefix: [Int]
  let loc: SourceLoc

  init(
    _ expected: Bool, _ sequence: [Int], _ prefix: [Int],
    _ expectedLeftoverSequence: [Int],
    _ expectedLeftoverPrefix: [Int],
    file: String = __FILE__, line: UWord = __LINE__
  ) {
    self.expected = expected
    self.sequence = sequence
    self.prefix = prefix
    self.expectedLeftoverSequence = expectedLeftoverSequence
    self.expectedLeftoverPrefix = expectedLeftoverPrefix
    self.loc = SourceLoc(file, line, comment: "test data")
  }
}

let startsWithTests = [
  // Corner cases.
  StartsWithTest(true, [], [], [], []),

  StartsWithTest(false, [], [ 1 ], [], []),
  StartsWithTest(true, [ 1 ], [], [], []),

  // Equal sequences.
  StartsWithTest(true, [ 1 ], [ 1 ], [], []),
  StartsWithTest(true, [ 1, 2 ], [ 1, 2 ], [], []),

  // Proper prefix.
  StartsWithTest(true, [ 0, 1, 2 ], [ 0, 1 ], [], []),
  StartsWithTest(false, [ 0, 1 ], [ 0, 1, 2 ], [], []),

  StartsWithTest(true, [ 1, 2, 3, 4 ], [ 1, 2 ], [ 4 ], []),
  StartsWithTest(false, [ 1, 2 ], [ 1, 2, 3, 4 ], [], [ 4 ]),

  // Not a prefix.
  StartsWithTest(false, [ 1, 2, 3, 4 ], [ 1, 2, 10 ], [ 4 ], []),
  StartsWithTest(false, [ 1, 2, 10 ], [ 1, 2, 3, 4 ], [], [ 4 ]),

  StartsWithTest(false, [ 1, 2, 3, 4, 10 ], [ 1, 2, 10 ], [ 4, 10 ], []),
  StartsWithTest(false, [ 1, 2, 10 ], [ 1, 2, 3, 4, 10 ], [], [ 4, 10 ]),
]

// FIXME(prext): remove this function.
func checkStartsWith(
  expected: Bool, sequence: [Int], prefix: [Int],
  stackTrace: SourceLocStack
) {
  expectEqual(expected, startsWith(sequence, prefix), stackTrace: stackTrace)
  expectEqual(
    expected, startsWith(sequence, prefix, (==)),
    stackTrace: stackTrace)
  expectEqual(
    expected, startsWith(sequence.map { $0 * 2 }, prefix) { $0 / 2 == $1 },
    stackTrace: stackTrace)

  // Test using different types for the sequence and prefix.
  expectEqual(
    expected, startsWith(ContiguousArray(sequence), prefix),
    stackTrace: stackTrace)
  expectEqual(
    expected, startsWith(ContiguousArray(sequence), prefix, (==)),
    stackTrace: stackTrace)
}

Algorithm.test("startsWith") {
  // FIXME(prext): remove these tests together with the startsWith() function when
  // protocol extensions land.  These tests have been migrated to the new API.

  for test in startsWithTests {
    checkStartsWith(
      test.expected, test.sequence, test.prefix, test.loc.withCurrentLoc())
  }
}

Algorithm.test("enumerate") {
  // FIXME(prext): remove these tests together with the enumerate() function when
  // protocol extensions land.  These tests have been migrated to the new API.

  var result = [String]()
  for (i, s) in enumerate( "You will never retrieve the necronomicon!"._split(" ") ) {
    result.append("\(i) \(s)")
  }
  expectEqual(
    [ "0 You", "1 will", "2 never", "3 retrieve", "4 the", "5 necronomicon!" ],
    result)
}

Algorithm.test("equal") {
  // FIXME(prext): remove these tests together with the equal() function when
  // protocol extensions land.  These tests have been migrated to the new API.

  var _0_4 = [0, 1, 2, 3]
  expectFalse(equal(_0_4, 0..<3))
  expectTrue(equal(_0_4, 0..<4))
  expectFalse(equal(_0_4, 0..<5))
  expectFalse(equal(_0_4, 1..<4))
}

Algorithm.test("equal/predicate") {
  func compare(lhs: (Int, Int), rhs: (Int, Int)) -> Bool {
    return lhs.0 == rhs.0 && lhs.1 == rhs.1
  }

  var _0_4 = [(0, 10), (1, 11), (2, 12), (3, 13)]
  expectFalse(equal(_0_4, [(0, 10), (1, 11), (2, 12)], compare))
  expectTrue(equal(_0_4, [(0, 10), (1, 11), (2, 12), (3, 13)], compare))
  expectFalse(equal(_0_4, [(0, 10), (1, 11), (2, 12), (3, 13), (4, 14)], compare))
  expectFalse(equal(_0_4, [(1, 11), (2, 12), (3, 13)], compare))
}

Algorithm.test("contains") {
  // FIXME(prext): remove these tests together with the contains() function when
  // protocol extensions land.  These tests have been migrated to the new API.

  let _0_4 = [0, 1, 2, 3]
  expectFalse(contains(_0_4, 7))
  expectTrue(contains(_0_4, 2))
  expectFalse(contains(_0_4, { $0 - 10 > 0  }))
  expectTrue(contains(_0_4, { $0 % 3 == 0 }))
}

Algorithm.test("min,max") {
  expectEqual(2, min(3, 2))
  expectEqual(3, min(3, 7, 5))
  expectEqual(3, max(3, 2))
  expectEqual(7, max(3, 7, 5))

  // FIXME: add tests that check that min/max return the
  // first element of the sequence (by reference equailty) that satisfy the
  // condition.
}

Algorithm.test("minElement,maxElement") {
  // FIXME(prext): remove these tests together with the minElement() function
  // when protocol extensions land.  These tests have been migrated to the new
  // API.

  var arr = [Int](count: 10, repeatedValue: 0)
  for i in 0..<10 {
    arr[i] = i % 7 + 2
  }
  expectEqual([2, 3, 4, 5, 6, 7, 8, 2, 3, 4], arr)

  expectEqual(2, minElement(arr))
  expectEqual(8, maxElement(arr))

  // min and max element of a slice
  expectEqual(3, minElement(arr[1..<5]))
  expectEqual(6, maxElement(arr[1..<5]))

  // FIXME: add tests that check that minElement/maxElement return the
  // first element of the sequence (by reference equailty) that satisfy the
  // condition.
}

Algorithm.test("filter/SequenceType") {
  // FIXME(prext): remove these tests together with the filter() function when
  // protocol extensions land.  These tests have been migrated to the new API.
  if true {
    let s = MinimalSequence<Int>([], underestimatedCount: .Overestimate)
    var result = filter(s) {
      (x: Int) -> Bool in
      expectUnreachable()
      return true
    }
    expectType([Int].self, &result)
    expectEqual([], result)
    expectEqual([], Array(s)) { "sequence should be consumed" }
    expectEqual(0, result.capacity)
  }
  if true {
    let s = MinimalSequence(
      [ 0, 30, 10, 90 ], underestimatedCount: .Overestimate)
    let result = filter(s) { (x: Int) -> Bool in false }
    expectEqual([], result)
    expectEqual([], Array(s)) { "sequence should be consumed" }
    expectEqual(0, result.capacity)
  }
  if true {
    let s = MinimalSequence(
      [ 0, 30, 10, 90 ], underestimatedCount: .Overestimate)
    let result = filter(s) { (x: Int) -> Bool in true }
    expectEqual([ 0, 30, 10, 90 ], result)
    expectEqual([], Array(s)) { "sequence should be consumed" }
    expectGE(2 * result.count, result.capacity)
  }
  if true {
    let s = MinimalSequence(
      [ 0, 30, 10, 90 ], underestimatedCount: .Value(0))
    let result = filter(s) { $0 % 3 == 0 }
    expectEqual([ 0, 30, 90 ], result)
    expectEqual([], Array(s)) { "sequence should be consumed" }
    expectGE(2 * result.count, result.capacity)
  }
  if true {
    let s = MinimalSequence(
      [ 0, 30, 10, 90 ], underestimatedCount: .Overestimate)
    let result = filter(s) { $0 % 3 == 0 }
    expectEqual([ 0, 30, 90 ], result)
    expectEqual([], Array(s)) { "sequence should be consumed" }
    expectGE(2 * result.count, result.capacity)
  }
}

Algorithm.test("filter/CollectionType") {
  // FIXME(prext): remove these tests together with the filter() function when
  // protocol extensions land.  These tests have been migrated to the new API.
  if true {
    let c = MinimalForwardCollection<Int>([])
    var result = filter(c) {
      (x: Int) -> Bool in
      expectUnreachable()
      return true
    }
    expectEqual([], result)
    expectType([Int].self, &result)
    expectEqual(0, result.capacity)
  }
  if true {
    let c = MinimalForwardCollection([ 0, 30, 10, 90 ])
    let result = filter(c) { (x: Int) -> Bool in false }
    expectEqual([], result)
    expectEqual(0, result.capacity)
  }
  if true {
    let c = MinimalForwardCollection([ 0, 30, 10, 90 ])
    let result = filter(c) { (x: Int) -> Bool in true }
    expectEqual([ 0, 30, 10, 90 ], result)
    expectGE(2 * result.count, result.capacity)
  }
  if true {
    let c = MinimalForwardCollection([ 0, 30, 10, 90 ])
    let result = filter(c) { $0 % 3 == 0 }
    expectEqual([ 0, 30, 90 ], result)
    expectGE(2 * result.count, result.capacity)
  }
}

Algorithm.test("filter/eager") {
  // Make sure filter is eager and only calls its predicate once per element.

  // FIXME(prext): remove these tests together with the filter() function when
  // protocol extensions land.  These tests have been migrated to the new API.
  var count = 0
  let one = filter(0..<10) {
    (x: Int)->Bool in ++count; return x == 1
  }
  for x in one {}
  expectEqual(10, count)
  for x in one {}
  expectEqual(10, count)
}

Algorithm.test("map/SequenceType") {
  // FIXME(prext): remove these tests together with the map() function when
  // protocol extensions land.  These tests have been migrated to the new API.

  if true {
    let s = MinimalSequence<Int>([], underestimatedCount: .Overestimate)
    var result = map(s) {
      (x: Int) -> Int16 in
      expectUnreachable()
      return 42
    }
    expectType([Int16].self, &result)
    expectEqual([], result)
    expectEqual([], Array(s))
    // FIXME: <rdar://problem/19810841> Reserve capacity when running map() over a SequenceType
    // expectLE(s.underestimatedCount, result.capacity)
  }
  if true {
    let s = MinimalSequence(
      [ 0, 30, 10, 90 ], underestimatedCount: .Value(0))
    let result = map(s) { $0 + 1 }
    expectEqual([ 1, 31, 11, 91 ], result)
    expectEqual([], Array(s))
    // FIXME: <rdar://problem/19810841> Reserve capacity when running map() over a SequenceType
    // expectLE(s.underestimatedCount, result.capacity)
  }
  if true {
    let s = MinimalSequence(
      [ 0, 30, 10, 90 ], underestimatedCount: .Overestimate)
    let result = map(s) { $0 + 1 }
    expectEqual([ 1, 31, 11, 91 ], result)
    expectEqual([], Array(s))
    // FIXME: <rdar://problem/19810841> Reserve capacity when running map() over a SequenceType
    // expectLE(s.underestimatedCount, result.capacity)
  }
}

Algorithm.test("map/CollectionType") {
  // FIXME(prext): remove these tests together with the map() function when
  // protocol extensions land.  These tests have been migrated to the new API.

  if true {
    let c = MinimalForwardCollection<Int>([])
    var result = map(c) {
      (x: Int) -> Int16 in
      expectUnreachable()
      return 42
    }
    expectType([Int16].self, &result)
    expectEqual([], result)
    expectLE(c.underestimatedCount, result.capacity)
    expectGE(result.count + 3, result.capacity) {
      "map() should use the precise element count"
    }
  }
  if true {
    let c = MinimalForwardCollection(
      [ 0, 30, 10, 90 ], underestimatedCount: .Value(0))
    let result = map(c) { $0 + 1 }
    expectEqual([ 1, 31, 11, 91 ], result)
    expectGE(result.count + 3, result.capacity) {
      "map() should use the precise element count"
    }
  }
}

Algorithm.test("flatMap/SequenceType") {
  // FIXME(prext): remove these tests together with the flatMap() function when
  // protocol extensions land.  These tests have been migrated to the new API.

  if true {
    let s = MinimalSequence<Int>([])
    var result = flatMap(s) {
      (x: Int) -> [Int16] in
      expectUnreachable()
      return [42]
    }
    expectType([Int16].self, &result)
    expectEqual([], result)
    expectEqual([], Array(s))
  }
  if true {
    let s = MinimalSequence([ 0, 30, 10, 90 ])
    let result = flatMap(s) { [$0 + 1] }
    expectEqual([ 1, 31, 11, 91 ], result)
    expectEqual([], Array(s))
  }
}

Algorithm.test("flatMap/CollectionType") {
  // FIXME(prext): remove these tests together with the flatMap() function when
  // protocol extensions land.  These tests have been migrated to the new API.

  if true {
    let c = MinimalForwardCollection<Int>([])
    var result = flatMap(c) {
      (x: Int) -> [Int16] in
      expectUnreachable()
      return [42]
    }
    expectType([Int16].self, &result)
    expectEqual([], result)
  }
  if true {
    let c = MinimalForwardCollection([ 0, 30, 10, 90 ])
    let result = flatMap(c) { [$0 + 1] }
    expectEqual([ 1, 31, 11, 91 ], result)
  }
}

Algorithm.test("sorted/strings")
  .xfail(.LinuxAny(reason: "String comparison: ICU vs. Foundation"))
  .code {
  expectEqual(
    [ "Banana", "apple", "cherry" ],
    sorted([ "apple", "Banana", "cherry" ]))

  let s = sorted(["apple", "Banana", "cherry"]) {
    count($0) > count($1)
  }
  expectEqual([ "Banana", "cherry", "apple" ], s)
}

// A wrapper around Array<T> that disables any type-specific algorithm
// optimizations and forces bounds checking on.
struct A<T> : MutableSliceable {
  init(_ a: Array<T>) {
    impl = a
  }

  var startIndex: Int {
    return 0
  }

  var endIndex: Int {
    return impl.count
  }

  func generate() -> Array<T>.Generator {
    return impl.generate()
  }

  subscript(i: Int) -> T {
    get {
      expectTrue(i >= 0 && i < impl.count)
      return impl[i]
    }
    set (x) {
      expectTrue(i >= 0 && i < impl.count)
      impl[i] = x
    }
  }

  subscript(r: Range<Int>) -> Array<T>.SubSlice {
    get {
      expectTrue(r.startIndex >= 0 && r.startIndex <= impl.count)
      expectTrue(r.endIndex >= 0 && r.endIndex <= impl.count)
      return impl[r]
    }
    set (x) {
      expectTrue(r.startIndex >= 0 && r.startIndex <= impl.count)
      expectTrue(r.endIndex >= 0 && r.endIndex <= impl.count)
      impl[r] = x
    }
  }

  var impl: Array<T>
}

func withInvalidOrderings(body: ((Int,Int)->Bool)->Void) {
  // Test some ordering predicates that don't create strict weak orderings
  body { (_,_) in true }
  body { (_,_) in false }
  var i = 0
  body { (_,_) in i++ % 2 == 0 }
  body { (_,_) in i++ % 3 == 0 }
  body { (_,_) in i++ % 5 == 0 }
}

func randomArray() -> A<Int> {
  let count = Int(rand32(exclusiveUpperBound: 50))
  return A(randArray(count))
}

Algorithm.test("invalidOrderings") {
  withInvalidOrderings {
    var a = randomArray()
    sort(&a, $0)
  }
  withInvalidOrderings {
    var a: A<Int>
    a = randomArray()
    partition(&a, indices(a), $0)
  }
  /*
  // FIXME: Disabled due to <rdar://problem/17734737> Unimplemented:
  // abstraction difference in l-value
  withInvalidOrderings {
    var a = randomArray()
    var pred = $0
    _insertionSort(&a, indices(a), &pred)
  }
  */
  withInvalidOrderings {
    let predicate: (Int,Int)->Bool = $0
    let result = lexicographicalCompare(randomArray(), randomArray(), isOrderedBefore: predicate)
  }
}

// The routine is based on http://www.cs.dartmouth.edu/~doug/mdmspe.pdf
func makeQSortKiller(len: Int) -> [Int] {
  var candidate: Int = 0
  var keys = [Int:Int]()
  func Compare(x: Int, y : Int) -> Bool {
    if keys[x] == nil && keys[y] == nil {
      if (x == candidate) {
        keys[x] = keys.count
      } else {
        keys[y] = keys.count
      }
    }
    if keys[x] == nil {
      candidate = x
      return true
    }
    if keys[y] == nil {
      candidate = y
      return false
    }
    return keys[x]! > keys[y]!
  }

  var ary = [Int](count: len, repeatedValue:0)
  var ret = [Int](count: len, repeatedValue:0)
  for i in 0..<len { ary[i] = i }
  ary = sorted(ary, Compare)
  for i in 0..<len {
    ret[ary[i]] = i
  }
  return ret
}

Algorithm.test("sorted/complexity") {
  var ary: [Int] = []

  // Check performance of sort on array of repeating values
  var comparisons_100 = 0
  ary = [Int](count: 100, repeatedValue: 0)
  sort(&ary) { comparisons_100++; return $0 < $1 }
  var comparisons_1000 = 0
  ary = [Int](count: 1000, repeatedValue: 0)
  sort(&ary) { comparisons_1000++; return $0 < $1 }
  expectTrue(comparisons_1000/comparisons_100 < 20)

  // Try to construct 'bad' case for quicksort, on which the algorithm
  // goes quadratic.
  comparisons_100 = 0
  ary = makeQSortKiller(100)
  sort(&ary) { comparisons_100++; return $0 < $1 }
  comparisons_1000 = 0
  ary = makeQSortKiller(1000)
  sort(&ary) { comparisons_1000++; return $0 < $1 }
  expectTrue(comparisons_1000/comparisons_100 < 20)
}

Algorithm.test("sorted/return type") {
  let x: Array = sorted([5, 4, 3, 2, 1] as ArraySlice)
}

/// A type that does not conform to any protocols.
///
/// This type can be used to check that generic functions don't rely on any
/// conformances.
public struct OpaqueValue<Underlying> {
  public var value: Underlying
  public var identity: Int

  public init(_ value: Underlying) {
    self.value = value
    self.identity = 0
  }

  public init(_ value: Underlying, identity: Int) {
    self.value = value
    self.identity = identity
  }
}

/// A type that conforms only to `Equatable`.
///
/// This type can be used to check that generic functions don't rely on any
/// other conformances.
public struct MinimalEquatableValue : Equatable {
  public static var timesEqualEqualWasCalled: Int = 0

  public var value: Int
  public var identity: Int

  public init(_ value: Int) {
    self.value = value
    self.identity = 0
  }

  public init(_ value: Int, identity: Int) {
    self.value = value
    self.identity = identity
  }
}
public func == (
  lhs: MinimalEquatableValue,
  rhs: MinimalEquatableValue
) -> Bool {
  ++MinimalEquatableValue.timesEqualEqualWasCalled
  return lhs.value == rhs.value
}

/// A type that conforms only to `Equatable` and `Hashable`.
///
/// This type can be used to check that generic functions don't rely on any
/// other conformances.
public struct MinimalHashableValue : Equatable, Hashable {
  public static var timesEqualEqualWasCalled: Int = 0
  public static var timesHashValueWasCalled: Int = 0

  public var value: Int
  public var identity: Int

  public init(_ value: Int) {
    self.value = value
    self.identity = 0
  }

  public init(_ value: Int, identity: Int) {
    self.value = value
    self.identity = identity
  }

  public var hashValue: Int {
    ++MinimalHashableValue.timesHashValueWasCalled
    return value.hashValue
  }
}

public func == (
  lhs: MinimalHashableValue,
  rhs: MinimalHashableValue
) -> Bool {
  ++MinimalHashableValue.timesEqualEqualWasCalled
  return lhs.value == rhs.value
}

/// A type that conforms only to `Equatable` and `Comparable`.
///
/// This type can be used to check that generic functions don't rely on any
/// other conformances.
public struct MinimalComparableValue : Equatable, Comparable {
  public static var timesEqualEqualWasCalled: Int = 0
  public static var timesLessWasCalled: Int = 0

  public var value: Int
  public var identity: Int

  public init(_ value: Int) {
    self.value = value
    self.identity = 0
  }

  public init(_ value: Int, identity: Int) {
    self.value = value
    self.identity = identity
  }
}

public func == (
  lhs: MinimalComparableValue,
  rhs: MinimalComparableValue
) -> Bool {
  ++MinimalComparableValue.timesEqualEqualWasCalled
  return lhs.value == rhs.value
}

public func < (
  lhs: MinimalComparableValue,
  rhs: MinimalComparableValue
) -> Bool {
  ++MinimalComparableValue.timesLessWasCalled
  return lhs.value < rhs.value
}

var SequenceTypeAlgorithms = TestSuite("SequenceTypeAlgorithms")

// FIXME: add tests for:
//
// - Array, ContiguousArray and ArraySlice as inputs.  These types special-case
// a lot of collection behavior for performance reasons.  Not to even mention
// that these are important types to test in any case.
//
// - NaN behavior of floating point types, combined with these generic
// algorithms, should make sense if possible.  For example,
// [1.0, Double.NaN].startsWith([1.0, 2.0]) should be false.

//===----------------------------------------------------------------------===//
// enumerate()
//===----------------------------------------------------------------------===//

struct EnumerateTest {
  let expected: [(Int, Int)]
  let sequence: [Int]
  let loc: SourceLoc

  init(
    _ expected: [(Int, Int)], _ sequence: [Int],
    file: String = __FILE__, line: UWord = __LINE__,
    comment: String = ""
  ) {
    self.expected = expected
    self.sequence = sequence
    self.loc = SourceLoc(file, line, comment: "test data" + comment)
  }
}

let enumerateTests = [
  EnumerateTest([], []),
  EnumerateTest([ (0, 10) ], [ 10 ]),
  EnumerateTest([ (0, 10), (1, 20) ], [ 10, 20 ]),
  EnumerateTest([ (0, 10), (1, 20), (2, 30) ], [ 10, 20, 30 ]),
]

SequenceTypeAlgorithms.test("enumerate") {
  typealias Element = (index: Int, element: OpaqueValue<Int>)
  func compareElements(lhs: Element, rhs: Element) -> Bool {
    return lhs.0 == rhs.0 && lhs.1.value == rhs.1.value
  }

  for test in enumerateTests {
    let s = MinimalSequence<OpaqueValue<Int>>(
      test.sequence._prext_map { OpaqueValue($0) })
    var result = s._prext_enumerate()
    expectType(
      EnumerateSequence<MinimalSequence<OpaqueValue<Int>>>.self,
      &result)
    checkSequence(
      test.expected._prext_map {
        (index: $0.0, element: OpaqueValue($0.1))
      } as [Element],
      result, compareElements,
      resiliencyChecks: .none,
      test.loc.withCurrentLoc())
    expectEqual([], s._prext_map { $0.value }) { "sequence should be consumed" }
  }
}

//===----------------------------------------------------------------------===//
// minElement(), maxElement()
//===----------------------------------------------------------------------===//

struct MinMaxElementTest {
  let expectedMinValue: Int?
  let expectedMinIndex: Int?
  let expectedMaxValue: Int?
  let expectedMaxIndex: Int?
  let sequence: [Int]
  let loc: SourceLoc

  init(
    minValue expectedMinValue: Int?,
    index expectedMinIndex: Int?,
    maxValue expectedMaxValue: Int?,
    index expectedMaxIndex: Int?,
    _ sequence: [Int],
    file: String = __FILE__, line: UWord = __LINE__,
    comment: String = ""
  ) {
    self.expectedMinValue = expectedMinValue
    self.expectedMinIndex = expectedMinIndex
    self.expectedMaxValue = expectedMaxValue
    self.expectedMaxIndex = expectedMaxIndex
    self.sequence = sequence
    self.loc = SourceLoc(file, line, comment: "test data" + comment)
  }
}

let minMaxElementTests = [
  MinMaxElementTest(
    minValue: nil, index: nil,
    maxValue: nil, index: nil,
    []),
  MinMaxElementTest(
    minValue: 42, index: 0,
    maxValue: 42, index: 0,
    [ 42 ]),
  MinMaxElementTest(
    minValue: -1, index: 1,
    maxValue: 30, index: 2,
    [ 10, -1, 30, -1, 30 ]),
  MinMaxElementTest(
    minValue: -2, index: 5,
    maxValue: 31, index: 6,
    [ 10, -1, 30, -1, 30, -2, 31 ]),
]

% for algorithmKind in [ 'min', 'max' ]:
%   AlgorithmKind = algorithmKind.capitalize()

SequenceTypeAlgorithms.test("${algorithmKind}Element/WhereElementIsComparable") {
  for test in minMaxElementTests {
    let s = MinimalSequence<MinimalComparableValue>(
      test.sequence._prext_enumerate()._prext_map {
        MinimalComparableValue($1, identity: $0)
      })
    var maybeResult = s._prext_${algorithmKind}Element()
    expectType(Optional<MinimalComparableValue>.self, &maybeResult)
    if let result? = maybeResult {
      expectEqual(
        test.expected${AlgorithmKind}Value!, result.value,
        stackTrace: test.loc.withCurrentLoc())
      expectEqual(
        test.expected${AlgorithmKind}Index!, result.identity,
        stackTrace: test.loc.withCurrentLoc())
    } else {
      expectEmpty(
        test.expected${AlgorithmKind}Value,
        stackTrace: test.loc.withCurrentLoc())
      expectEmpty(
        test.expected${AlgorithmKind}Index,
        stackTrace: test.loc.withCurrentLoc())
    }
    expectEqual([], s._prext_map { $0.value }) { "sequence should be consumed" }
  }
}

SequenceTypeAlgorithms.test("${algorithmKind}Element/Predicate") {
  for test in minMaxElementTests {
    let s = MinimalSequence<OpaqueValue<Int>>(
      test.sequence._prext_enumerate()._prext_map {
        OpaqueValue($1, identity: $0)
      })
    var timesClosureWasCalled = 0
    var maybeResult = s._prext_${algorithmKind}Element {
      (lhs, rhs) -> Bool in
      ++timesClosureWasCalled
      return lhs.value < rhs.value
    }
    expectType(Optional<OpaqueValue<Int>>.self, &maybeResult)
    if let result? = maybeResult {
      expectEqual(
        test.expected${AlgorithmKind}Value!, result.value,
        stackTrace: test.loc.withCurrentLoc())
      expectEqual(
        test.expected${AlgorithmKind}Index!, result.identity,
        stackTrace: test.loc.withCurrentLoc())
    } else {
      expectEmpty(
        test.expected${AlgorithmKind}Value,
        stackTrace: test.loc.withCurrentLoc())
      expectEmpty(
        test.expected${AlgorithmKind}Index,
        stackTrace: test.loc.withCurrentLoc())
    }
    expectEqual([], s._prext_map { $0.value }) { "sequence should be consumed" }
    expectEqual(max(0, test.sequence.count - 1), timesClosureWasCalled) {
      "maxElement() should be eager and should only call its predicate once per element"
    }
  }
}

% end

//===----------------------------------------------------------------------===//
// startsWith()
//===----------------------------------------------------------------------===//

SequenceTypeAlgorithms.test("startsWith/WhereElementIsEquatable") {
  for test in startsWithTests {
    if true {
      let s = MinimalSequence<MinimalEquatableValue>(
        test.sequence.map { MinimalEquatableValue($0) })
      let prefix = MinimalSequence<MinimalEquatableValue>(
        test.prefix.map { MinimalEquatableValue($0) })
      expectEqual(
        test.expected,
        s._prext_startsWith(prefix),
        stackTrace: test.loc.withCurrentLoc())
      expectEqual(
        test.expectedLeftoverSequence, s._prext_map { $0.value },
        stackTrace: test.loc.withCurrentLoc())
      expectEqual(
        test.expectedLeftoverPrefix, prefix._prext_map { $0.value },
        stackTrace: test.loc.withCurrentLoc())
    }

    // Use different types for the sequence and prefix.
    if true {
      let s = MinimalForwardCollection<MinimalEquatableValue>(
        test.sequence.map { MinimalEquatableValue($0) })
      let prefix = MinimalSequence<MinimalEquatableValue>(
        test.prefix.map { MinimalEquatableValue($0) })
      expectEqual(
        test.expected,
        s._prext_startsWith(prefix),
        stackTrace: test.loc.withCurrentLoc())
      expectEqual(
        test.sequence, s._prext_map { $0.value },
        stackTrace: test.loc.withCurrentLoc())
      expectEqual(
        test.expectedLeftoverPrefix, prefix._prext_map { $0.value },
        stackTrace: test.loc.withCurrentLoc())
    }
  }
}

SequenceTypeAlgorithms.test("startsWith/Predicate") {
  for test in startsWithTests {
    if true {
      let s = MinimalSequence<OpaqueValue<Int>>(
        map(test.sequence) { OpaqueValue($0) })
      let prefix = MinimalSequence<OpaqueValue<Int>>(
        map(test.prefix) { OpaqueValue($0) })
      expectEqual(
        test.expected,
        s._prext_startsWith(prefix) { $0.value == $1.value },
        stackTrace: test.loc.withCurrentLoc())
      expectEqual(
        test.expectedLeftoverSequence, s._prext_map { $0.value },
        stackTrace: test.loc.withCurrentLoc())
      expectEqual(
        test.expectedLeftoverPrefix, prefix._prext_map { $0.value },
        stackTrace: test.loc.withCurrentLoc())
    }
    if true {
      let s = MinimalSequence<OpaqueValue<Int>>(
        map(test.sequence) { OpaqueValue($0 * 2) })
      let prefix = MinimalSequence<OpaqueValue<Int>>(
        map(test.prefix) { OpaqueValue($0) })
      expectEqual(
        test.expected,
        s._prext_startsWith(prefix) { $0.value / 2 == $1.value },
        stackTrace: test.loc.withCurrentLoc())
      expectEqual(
        test.expectedLeftoverSequence, s._prext_map { $0.value / 2 },
        stackTrace: test.loc.withCurrentLoc())
      expectEqual(
        test.expectedLeftoverPrefix, prefix._prext_map { $0.value },
        stackTrace: test.loc.withCurrentLoc())
    }

    // Use different types for the sequence and prefix.
    if true {
      let s = MinimalForwardCollection<OpaqueValue<Int>>(
        map(test.sequence) { OpaqueValue($0) })
      let prefix = MinimalSequence<OpaqueValue<Int>>(
        map(test.prefix) { OpaqueValue($0) })
      expectEqual(
        test.expected,
        s._prext_startsWith(prefix) { $0.value == $1.value },
        stackTrace: test.loc.withCurrentLoc())
      expectEqual(
        test.sequence, s._prext_map { $0.value },
        stackTrace: test.loc.withCurrentLoc())
      expectEqual(
        test.expectedLeftoverPrefix, prefix._prext_map { $0.value },
        stackTrace: test.loc.withCurrentLoc())
    }
  }
}

//===----------------------------------------------------------------------===//
// equal()
//===----------------------------------------------------------------------===//

struct EqualElementsTest {
  let expected: Bool
  let sequence: [Int]
  let other: [Int]
  let expectedLeftoverSequence: [Int]
  let expectedLeftoverOther: [Int]
  let loc: SourceLoc

  init(
    _ expected: Bool, _ sequence: [Int], _ other: [Int],
    _ expectedLeftoverSequence: [Int],
    _ expectedLeftoverOther: [Int],
    file: String = __FILE__, line: UWord = __LINE__,
    comment: String = ""
  ) {
    self.expected = expected
    self.sequence = sequence
    self.other = other
    self.expectedLeftoverSequence = expectedLeftoverSequence
    self.expectedLeftoverOther = expectedLeftoverOther
    self.loc = SourceLoc(file, line, comment: "test data" + comment)
  }

  func flip() -> EqualElementsTest {
    return EqualElementsTest(
      expected, other, sequence,
      expectedLeftoverOther, expectedLeftoverSequence,
      file: loc.file, line: loc.line, comment: " (flipped)")
  }
}

let equalElementsTests = [
  EqualElementsTest(true, [], [], [], []),

  EqualElementsTest(false, [ 1 ], [], [], []),
  EqualElementsTest(false, [], [ 1 ], [], []),

  EqualElementsTest(false, [ 1, 2 ], [], [ 2 ], []),
  EqualElementsTest(false, [], [ 1, 2 ], [], [ 2 ]),

  EqualElementsTest(false, [ 1, 2, 3, 4 ], [ 1, 2 ], [ 4 ], []),
  EqualElementsTest(false, [ 1, 2 ], [ 1, 2, 3, 4 ], [], [ 4 ]),
].flatMap { [ $0, $0.flip() ] }

SequenceTypeAlgorithms.test("equalElements/WhereElementIsEquatable") {
  for test in equalElementsTests {
    if true {
      let s = MinimalSequence<MinimalEquatableValue>(
        test.sequence.map { MinimalEquatableValue($0) })
      let other = MinimalSequence<MinimalEquatableValue>(
        test.other.map { MinimalEquatableValue($0) })
      expectEqual(
        test.expected,
        s._prext_equalElements(other),
        stackTrace: test.loc.withCurrentLoc())
      expectEqual(
        test.expectedLeftoverSequence, s._prext_map { $0.value },
        stackTrace: test.loc.withCurrentLoc())
      expectEqual(
        test.expectedLeftoverOther, other._prext_map { $0.value },
        stackTrace: test.loc.withCurrentLoc())
    }

    // Use different types for the sequence and other.
    if true {
      let s = MinimalForwardCollection<MinimalEquatableValue>(
        test.sequence.map { MinimalEquatableValue($0) })
      let other = MinimalSequence<MinimalEquatableValue>(
        test.other.map { MinimalEquatableValue($0) })
      expectEqual(
        test.expected,
        s._prext_equalElements(other),
        stackTrace: test.loc.withCurrentLoc())
      expectEqual(
        test.sequence, s._prext_map { $0.value },
        stackTrace: test.loc.withCurrentLoc())
      expectEqual(
        test.expectedLeftoverOther, other._prext_map { $0.value },
        stackTrace: test.loc.withCurrentLoc())
    }
  }
}

SequenceTypeAlgorithms.test("equalElements/Predicate") {
  for test in equalElementsTests {
    if true {
      let s = MinimalSequence<OpaqueValue<Int>>(
        test.sequence.map { OpaqueValue($0) })
      let other = MinimalSequence<OpaqueValue<Int>>(
        test.other.map { OpaqueValue($0) })
      expectEqual(
        test.expected,
        s._prext_equalElements(other) { $0.value == $1.value },
        stackTrace: test.loc.withCurrentLoc())
      expectEqual(
        test.expectedLeftoverSequence, s._prext_map { $0.value },
        stackTrace: test.loc.withCurrentLoc())
      expectEqual(
        test.expectedLeftoverOther, other._prext_map { $0.value },
        stackTrace: test.loc.withCurrentLoc())
    }

    // Use different types for the sequence and other.
    if true {
      let s = MinimalForwardCollection<OpaqueValue<Int>>(
        test.sequence.map { OpaqueValue($0) })
      let other = MinimalSequence<OpaqueValue<Int>>(
        test.other.map { OpaqueValue($0) })
      expectEqual(
        test.expected,
        s._prext_equalElements(other) { $0.value == $1.value },
        stackTrace: test.loc.withCurrentLoc())
      expectEqual(
        test.sequence, s._prext_map { $0.value },
        stackTrace: test.loc.withCurrentLoc())
      expectEqual(
        test.expectedLeftoverOther, other._prext_map { $0.value },
        stackTrace: test.loc.withCurrentLoc())
    }
  }
}

//===----------------------------------------------------------------------===//
// lexicographicalCompare()
//===----------------------------------------------------------------------===//

struct LexicographicalCompareTest {
  let expected: ExpectedComparisonResult
  let sequence: [Int]
  let other: [Int]
  let expectedLeftoverSequence: [Int]
  let expectedLeftoverOther: [Int]
  let loc: SourceLoc

  init(
    _ expected: ExpectedComparisonResult, _ sequence: [Int], _ other: [Int],
    _ expectedLeftoverSequence: [Int],
    _ expectedLeftoverOther: [Int],
    file: String = __FILE__, line: UWord = __LINE__,
    comment: String = ""
  ) {
    self.expected = expected
    self.sequence = sequence
    self.other = other
    self.expectedLeftoverSequence = expectedLeftoverSequence
    self.expectedLeftoverOther = expectedLeftoverOther
    self.loc = SourceLoc(file, line, comment: "test data" + comment)
  }

  func flip() -> LexicographicalCompareTest {
    return LexicographicalCompareTest(
      expected.flip(), other, sequence,
      expectedLeftoverOther, expectedLeftoverSequence,
      file: loc.file, line: loc.line, comment: " (flipped)")
  }
}

let lexicographicalCompareTests = [
  LexicographicalCompareTest(.EQ, [], [], [], []),
  LexicographicalCompareTest(.EQ, [ 1 ], [ 1 ], [], []),

  LexicographicalCompareTest(.GT, [ 1 ], [], [], []),

  LexicographicalCompareTest(.GT, [ 1 ], [ 0 ], [], []),
  LexicographicalCompareTest(.EQ, [ 1 ], [ 1 ], [], []),
  LexicographicalCompareTest(.LT, [ 1 ], [ 2 ], [], []),

  LexicographicalCompareTest(.GT, [ 1, 2 ], [], [ 2 ], []),

  LexicographicalCompareTest(.GT, [ 1, 2 ], [ 0 ], [ 2 ], []),
  LexicographicalCompareTest(.GT, [ 1, 2 ], [ 1 ], [], []),
  LexicographicalCompareTest(.LT, [ 1, 2 ], [ 2 ], [ 2 ], []),

  LexicographicalCompareTest(.GT, [ 1, 2 ], [ 0, 0 ], [ 2 ], [ 0 ]),
  LexicographicalCompareTest(.GT, [ 1, 2 ], [ 1, 0 ], [], []),
  LexicographicalCompareTest(.LT, [ 1, 2 ], [ 2, 0 ], [ 2 ], [ 0 ]),

  LexicographicalCompareTest(.GT, [ 1, 2 ], [ 0, 1 ], [ 2 ], [ 1 ]),
  LexicographicalCompareTest(.GT, [ 1, 2 ], [ 1, 1 ], [], []),
  LexicographicalCompareTest(.LT, [ 1, 2 ], [ 2, 1 ], [ 2 ], [ 1 ]),

  LexicographicalCompareTest(.GT, [ 1, 2 ], [ 0, 2 ], [ 2 ], [ 2 ]),
  LexicographicalCompareTest(.EQ, [ 1, 2 ], [ 1, 2 ], [], []),
  LexicographicalCompareTest(.LT, [ 1, 2 ], [ 2, 2 ], [ 2 ], [ 2 ]),

  LexicographicalCompareTest(.GT, [ 1, 2 ], [ 0, 3 ], [ 2 ], [ 3 ]),
  LexicographicalCompareTest(.LT, [ 1, 2 ], [ 1, 3 ], [], []),
  LexicographicalCompareTest(.LT, [ 1, 2 ], [ 2, 3 ], [ 2 ], [ 3 ]),
].flatMap { [ $0, $0.flip() ] }

SequenceTypeAlgorithms.test("lexicographicalCompare/WhereElementIsComparable") {
  for test in lexicographicalCompareTests {
    if true {
      let s = MinimalSequence<MinimalComparableValue>(
        test.sequence.map { MinimalComparableValue($0) })
      let other = MinimalSequence<MinimalComparableValue>(
        test.other.map { MinimalComparableValue($0) })
      expectEqual(
        test.expected.isLT(),
        s._prext_lexicographicalCompare(other),
        stackTrace: test.loc.withCurrentLoc())
      expectEqual(
        test.expectedLeftoverSequence, s._prext_map { $0.value },
        stackTrace: test.loc.withCurrentLoc())
      expectEqual(
        test.expectedLeftoverOther, other._prext_map { $0.value },
        stackTrace: test.loc.withCurrentLoc())
    }

    // Use different types for the sequence and other.
    if true {
      let s = MinimalForwardCollection<MinimalComparableValue>(
        test.sequence.map { MinimalComparableValue($0) })
      let other = MinimalSequence<MinimalComparableValue>(
        test.other.map { MinimalComparableValue($0) })
      expectEqual(
        test.expected.isLT(),
        s._prext_lexicographicalCompare(other),
        stackTrace: test.loc.withCurrentLoc())
      expectEqual(
        test.sequence, s._prext_map { $0.value },
        stackTrace: test.loc.withCurrentLoc())
      expectEqual(
        test.expectedLeftoverOther, other._prext_map { $0.value },
        stackTrace: test.loc.withCurrentLoc())
    }
  }
}

SequenceTypeAlgorithms.test("lexicographicalCompare/Predicate") {
  for test in lexicographicalCompareTests {
    if true {
      let s = MinimalSequence<OpaqueValue<Int>>(
        test.sequence.map { OpaqueValue($0) })
      let other = MinimalSequence<OpaqueValue<Int>>(
        test.other.map { OpaqueValue($0) })
      expectEqual(
        test.expected.isLT(),
        s._prext_lexicographicalCompare(other) { $0.value < $1.value },
        stackTrace: test.loc.withCurrentLoc())
      expectEqual(
        test.expectedLeftoverSequence, s._prext_map { $0.value },
        stackTrace: test.loc.withCurrentLoc())
      expectEqual(
        test.expectedLeftoverOther, other._prext_map { $0.value },
        stackTrace: test.loc.withCurrentLoc())
    }

    // Use different types for the sequence and other.
    if true {
      let s = MinimalForwardCollection<OpaqueValue<Int>>(
        test.sequence.map { OpaqueValue($0) })
      let other = MinimalSequence<OpaqueValue<Int>>(
        test.other.map { OpaqueValue($0) })
      expectEqual(
        test.expected.isLT(),
        s._prext_lexicographicalCompare(other) { $0.value < $1.value },
        stackTrace: test.loc.withCurrentLoc())
      expectEqual(
        test.sequence, s._prext_map { $0.value },
        stackTrace: test.loc.withCurrentLoc())
      expectEqual(
        test.expectedLeftoverOther, other._prext_map { $0.value },
        stackTrace: test.loc.withCurrentLoc())
    }
  }
}

//===----------------------------------------------------------------------===//
// contains()
//===----------------------------------------------------------------------===//

// These tests are shared between find() and contains().
struct FindTest {
  let expected: Int?
  let element: Int
  let sequence: [Int]
  let expectedLeftoverSequence: [Int]
  let loc: SourceLoc

  init(
    _ expected: Int?, _ element: Int, _ sequence: [Int],
    _ expectedLeftoverSequence: [Int],
    file: String = __FILE__, line: UWord = __LINE__
  ) {
    self.expected = expected
    self.element = element
    self.sequence = sequence
    self.expectedLeftoverSequence = expectedLeftoverSequence
    self.loc = SourceLoc(file, line, comment: "test data")
  }
}

let findTests = [
  FindTest(nil, 42, [], []),

  FindTest(nil, 42, [ 1 ], []),
  FindTest(0, 1, [ 1 ], []),

  FindTest(nil, 42, [ 1, 2, 3, 4 ], []),
  FindTest(0, 1, [ 1, 2, 3, 4 ], [ 2, 3, 4 ]),
  FindTest(1, 2, [ 1, 2, 3, 4 ], [ 3, 4 ]),
  FindTest(2, 3, [ 1, 2, 3, 4 ], [ 4 ]),
  FindTest(3, 4, [ 1, 2, 3, 4 ], []),
]

func callStaticContains(
  sequence: MinimalSequence<MinimalEquatableValue>,
  element: MinimalEquatableValue) -> Bool {
  return sequence._prext_contains(element)
}

func callGenericContains<
  S : SequenceType where S.Generator.Element : Equatable
>(sequence: S, element: S.Generator.Element) -> Bool {
  return sequence._prext_contains(element)
}

% for dispatch in [ 'Static', 'Generic' ]:

SequenceTypeAlgorithms.test("contains/WhereElementIsEquatable/${dispatch}") {
  for test in findTests {
    let s = MinimalSequence<MinimalEquatableValue>(
      test.sequence.map { MinimalEquatableValue($0) })
    expectEqual(
      test.expected != nil,
      call${dispatch}Contains(s, MinimalEquatableValue(test.element)),
      stackTrace: test.loc.withCurrentLoc())
    expectEqual(
      test.expectedLeftoverSequence, s._prext_map { $0.value },
      stackTrace: test.loc.withCurrentLoc())
  }
}

% end

SequenceTypeAlgorithms.test("contains/Predicate") {
  for test in findTests {
    let s = MinimalSequence<OpaqueValue<Int>>(
      test.sequence.map { OpaqueValue($0) })
    expectEqual(
      test.expected != nil,
      s._prext_contains { $0.value == test.element },
      stackTrace: test.loc.withCurrentLoc())
    expectEqual(
      test.expectedLeftoverSequence, s._prext_map { $0.value },
      stackTrace: test.loc.withCurrentLoc())
  }
}

//===----------------------------------------------------------------------===//
// reduce()
//===----------------------------------------------------------------------===//

struct ReduceTest {
  let sequence: [Int]
  let loc: SourceLoc

  init(
    _ sequence: [Int],
    file: String = __FILE__, line: UWord = __LINE__
  ) {
    self.sequence = sequence
    self.loc = SourceLoc(file, line, comment: "test data")
  }
}

let reduceTests = [
  ReduceTest([]),
  ReduceTest([ 1 ]),
  ReduceTest([ 1, 2 ]),
  ReduceTest([ 1, 2, 3 ]),
  ReduceTest([ 1, 2, 3, 4, 5, 6, 7 ]),
]

SequenceTypeAlgorithms.test("reduce") {
  for test in reduceTests {
    let s = MinimalSequence<OpaqueValue<Int>>(
      test.sequence.map { OpaqueValue($0) })
    var timesClosureWasCalled = 0
    let result = s._prext_reduce(OpaqueValue<[Int]>([])) {
      (partialResult: OpaqueValue<[Int]>, element: OpaqueValue<Int>)
        -> OpaqueValue<[Int]> in
      ++timesClosureWasCalled
      return OpaqueValue<[Int]>(partialResult.value + [ element.value ])
    }
    expectEqual(test.sequence, result.value)
    expectEqual([], s._prext_map { $0.value }) { "sequence should be consumed" }
    expectEqual(test.sequence.count, timesClosureWasCalled) {
      "reduce() should be eager and should only call its predicate once per element"
    }
  }
}

//===----------------------------------------------------------------------===//
// reverse()
//===----------------------------------------------------------------------===//

struct ReverseTest {
  let expected: [Int]
  let sequence: [Int]
  let loc: SourceLoc

  init(
    _ expected: [Int], _ sequence: [Int],
    file: String = __FILE__, line: UWord = __LINE__
  ) {
    self.expected = expected
    self.sequence = sequence
    self.loc = SourceLoc(file, line, comment: "test data")
  }
}

let reverseTests = [
  ReverseTest([], []),
  ReverseTest([ 1 ], [ 1 ]),
  ReverseTest([ 2, 1 ], [ 1, 2 ]),
  ReverseTest([ 3, 2, 1 ], [ 1, 2, 3 ]),
  ReverseTest([ 4, 3, 2, 1 ], [ 1, 2, 3, 4]),
  ReverseTest(
    [ 7, 6, 5, 4, 3, 2, 1 ],
    [ 1, 2, 3, 4, 5, 6, 7 ]),
]

SequenceTypeAlgorithms.test("reverse/SequenceType") {
  for test in reverseTests {
    let s = MinimalSequence<OpaqueValue<Int>>(
      test.sequence.map { OpaqueValue($0) })
    var result = s._prext_reverse()
    expectType([OpaqueValue<Int>].self, &result)
    expectEqual(
      test.expected, result.map { $0.value },
      stackTrace: test.loc.withCurrentLoc())
    expectEqual([], s._prext_map { $0.value }) { "sequence should be consumed" }
  }
}

SequenceTypeAlgorithms.test("reverse/WhereIndexIsBidirectional,BidirectionalReverseView") {
  for test in reverseTests {
    let s = MinimalBidirectionalCollection<OpaqueValue<Int>>(
      test.sequence.map { OpaqueValue($0) })
    var result = s._prext_reverse()
    expectType(
      BidirectionalReverseView<MinimalBidirectionalCollection<OpaqueValue<Int>>>.self,
      &result)
    expectEqual(
      test.expected, result._prext_map { $0.value },
      stackTrace: test.loc.withCurrentLoc())

    // Check BidirectionalReverseView CollectionType conformance.
    checkBidirectionalCollection(
      test.expected.map { OpaqueValue($0) },
      result,
      { $0.value == $1.value },
      test.loc.withCurrentLoc())
  }
}

SequenceTypeAlgorithms.test("reverse/WhereIndexIsRandomAccess,RandomAccessReverseView") {
  for test in reverseTests {
    let s = MinimalRandomAccessCollection<OpaqueValue<Int>>(
      test.sequence.map { OpaqueValue($0) })
    var result = s._prext_reverse()
    expectType(
      RandomAccessReverseView<MinimalRandomAccessCollection<OpaqueValue<Int>>>.self,
      &result)
    expectEqual(
      test.expected, result._prext_map { $0.value },
      stackTrace: test.loc.withCurrentLoc())

    // Check RandomAccessReverseView CollectionType conformance.
    checkRandomAccessCollection(
      test.expected.map { OpaqueValue($0) },
      result,
      { $0.value == $1.value },
      test.loc.withCurrentLoc())
  }
}

//===----------------------------------------------------------------------===//
// filter()
//===----------------------------------------------------------------------===//

struct FilterTest {
  let expected: [Int]
  let sequence: [Int]
  let includeElement: (Int) -> Bool
  let loc: SourceLoc

  init(
    _ expected: [Int],
    _ sequence: [Int],
    _ includeElement: (Int) -> Bool,
    file: String = __FILE__, line: UWord = __LINE__
  ) {
    self.expected = expected
    self.sequence = sequence
    self.includeElement = includeElement
    self.loc = SourceLoc(file, line, comment: "test data")
  }
}

let filterTests = [
  FilterTest(
    [], [],
    { (x: Int) -> Bool in expectUnreachable(); return true }),

  FilterTest([], [ 0, 30, 10, 90 ], { (x: Int) -> Bool in false }),
  FilterTest(
    [ 0, 30, 10, 90 ], [ 0, 30, 10, 90 ], { (x: Int) -> Bool in true }
  ),
  FilterTest(
    [ 0, 30, 90 ], [ 0, 30, 10, 90 ], { (x: Int) -> Bool in x % 3 == 0 }
  ),
]

func callStaticSequenceFilter(
  sequence: MinimalSequence<OpaqueValue<Int>>,
  @noescape includeElement: (OpaqueValue<Int>) -> Bool
) -> [OpaqueValue<Int>] {
  var result = sequence._prext_filter(includeElement)
  expectType([OpaqueValue<Int>].self, &result)
  return result
}

func callGenericSequenceFilter<S : SequenceType>(
  sequence: S,
  @noescape includeElement: (S.Generator.Element) -> Bool
) -> [S.Generator.Element] {
  var result = sequence._prext_filter(includeElement)
  expectType(Array<S.Generator.Element>.self, &result)
  return result
}

% for dispatch in [ 'Static', 'Generic' ]:

SequenceTypeAlgorithms.test("filter/SequenceType/${dispatch}") {
  expectEqual(0, LifetimeTracked.instances)
  for test in filterTests {
    for underestimateCountBehavior in [
      UnderestimateCountBehavior.Overestimate,
      UnderestimateCountBehavior.Value(0)
    ] {
      let s = MinimalSequence<OpaqueValue<Int>>(
        test.sequence.map { OpaqueValue($0) },
        underestimatedCount: underestimateCountBehavior)
      let closureLifetimeTracker = LifetimeTracked(0)
      expectEqual(1, LifetimeTracked.instances)
      var timesClosureWasCalled = 0
      var result = call${dispatch}SequenceFilter(s) {
        (element) in
        _blackHole(closureLifetimeTracker)
        ++timesClosureWasCalled
        return test.includeElement(element.value)
      }
      expectType([OpaqueValue<Int>].self, &result)
      expectEqual(test.expected, map(result) { $0.value })
      expectEqual([], s._prext_map { $0.value }) { "sequence should be consumed" }
      expectEqual(test.sequence.count, timesClosureWasCalled) {
        "filter() should be eager and should only call its predicate once per element"
      }
      expectGE(2 * result.count, result.capacity) {
        "filter() should not reserve capacity (it does not know how much the predicate will filter out)"
      }
    }
  }
  expectEqual(0, LifetimeTracked.instances)
}

% end

func callGenericCollectionFilter<C : RangeReplaceableCollectionType>(
  collection: C,
  @noescape includeElement: (C.Generator.Element) -> Bool
) -> C {
  var result = collection._prext_filter(includeElement)
  expectType(C.self, &result)
  return result
}

% for Implementation in [ 'Default', 'Custom' ]:
%   CollectionType = 'RangeReplaceableCollectionWith%sFilterMethod' % Implementation

struct ${CollectionType} : RangeReplaceableCollectionType {

%   if Implementation == 'Custom':
  static var timesFilterWasCalled = 0
%   end

  var elements: [OpaqueValue<Int>]
  var reservedCapacity: Int = 0

  init() {
    self.elements = []
  }

  init(_ elements: [OpaqueValue<Int>]) {
    self.elements = elements
  }

  func generate() -> MinimalGenerator<OpaqueValue<Int>> {
    return MinimalSequence<OpaqueValue<Int>>(elements).generate()
  }

  var startIndex: MinimalForwardIndex {
    return MinimalForwardIndex(
      position: 0,
      startIndex: 0,
      endIndex: elements.endIndex)
  }

  var endIndex: MinimalForwardIndex {
    return MinimalForwardIndex(
      position: elements.endIndex,
      startIndex: 0,
      endIndex: elements.endIndex)
  }

  subscript(i: MinimalForwardIndex) -> OpaqueValue<Int> {
    return OpaqueValue(i.position + 1)
  }

  mutating func reserveCapacity(n: Int) {
    elements.reserveCapacity(n)
    reservedCapacity = max(reservedCapacity, n)
  }

  mutating func append(x: OpaqueValue<Int>) {
    elements.append(x)
  }

  mutating func extend<
    S : SequenceType where S.Generator.Element == OpaqueValue<Int>
  >(newElements: S) {
    expectUnreachable()
  }

  mutating func replaceRange<
    C : CollectionType where C.Generator.Element == OpaqueValue<Int>
  >(
    subRange: Range<MinimalForwardIndex>, with newElements: C
  ) {
    expectUnreachable()
  }

  mutating func insert(
    newElement: OpaqueValue<Int>, atIndex i: MinimalForwardIndex
  ) {
    expectUnreachable()
  }

  mutating func splice<
    S : CollectionType where S.Generator.Element == OpaqueValue<Int>
  >(newElements: S, atIndex i: MinimalForwardIndex) {
    expectUnreachable()
  }

  mutating func removeAtIndex(i: MinimalForwardIndex) -> OpaqueValue<Int> {
    expectUnreachable()
    return OpaqueValue(0xffff)
  }

  mutating func removeRange(subRange: Range<MinimalForwardIndex>) {
    expectUnreachable()
  }

  mutating func removeAll(keepCapacity: Bool = false) {
    expectUnreachable()
  }

%   if Implementation == 'Custom':

  func _prext_filter(
    @noescape includeElement: (OpaqueValue<Int>) -> Bool
  ) -> ${CollectionType} {
    ++RangeReplaceableCollectionWithCustomFilterMethod.timesFilterWasCalled
    return ${CollectionType}(elements._prext_filter(includeElement))
  }

%   end
}

% end

% for (CollectionType, CollectionKind) in [
%   ('MinimalForwardRangeReplaceableCollectionType<OpaqueValue<Int>>', 'Minimal'),
%   ('RangeReplaceableCollectionWithDefaultFilterMethod', 'DefaultImplementation'),
%   ('RangeReplaceableCollectionWithCustomFilterMethod', 'CustomImplementation'),
%   ('Array<OpaqueValue<Int>>', 'StdlibArray'),
%   ('ContiguousArray<OpaqueValue<Int>>', 'StdlibArray'),
%   ('ArraySlice<OpaqueValue<Int>>', 'StdlibArray')
% ]:

%   for dispatch in [ 'Static', 'Generic' ]:

%     if dispatch == 'Static':

func callStaticCollectionFilter(
  collection: ${CollectionType},
  @noescape includeElement: (OpaqueValue<Int>) -> Bool
) -> ${CollectionType} {
  var result = collection._prext_filter(includeElement)
  expectType(${CollectionType}.self, &result)
  return result
}

%     end

SequenceTypeAlgorithms.test("filter/RangeReplaceableCollectionType/${CollectionType}/${dispatch}") {
  expectEqual(0, LifetimeTracked.instances)
  for test in filterTests {
    for underestimateCountBehavior in [
      UnderestimateCountBehavior.Overestimate,
      UnderestimateCountBehavior.Value(0)
    ] {
%     if CollectionKind == 'Minimal':
      let s = ${CollectionType}(
        test.sequence.map { OpaqueValue($0) },
        underestimatedCount: underestimateCountBehavior)
%     else:
      let s = ${CollectionType}(
        test.sequence.map { OpaqueValue($0) })
%     end
%     if CollectionKind == 'CustomImplementation':
      RangeReplaceableCollectionWithCustomFilterMethod.timesFilterWasCalled = 0
%     end
      let closureLifetimeTracker = LifetimeTracked(0)
      expectEqual(1, LifetimeTracked.instances)
      var timesClosureWasCalled = 0
      var result = call${dispatch}CollectionFilter(s) {
        (element) in
        _blackHole(closureLifetimeTracker)
        ++timesClosureWasCalled
        return test.includeElement(element.value)
      }
      expectType(${CollectionType}.self, &result)
      expectEqual(
        test.expected, result._prext_map { $0.value },
        stackTrace: test.loc.withCurrentLoc())
%     if CollectionKind == 'CustomImplementation':
      expectEqual(
        1,
        RangeReplaceableCollectionWithCustomFilterMethod.timesFilterWasCalled)
%     end
      expectEqual(test.sequence, s._prext_map { $0.value }) {
        "collection should not be consumed"
      }
      expectEqual(test.sequence.count, timesClosureWasCalled) {
        "filter() should be eager and should only call its predicate once per element"
      }
      expectGE(2 * count(result), result.${'capacity' if CollectionKind == 'StdlibArray' else 'reservedCapacity'}) {
        "filter() should not reserve capacity (it does not know how much the predicate will filter out)"
      }
    }
  }
  expectEqual(0, LifetimeTracked.instances)
}

%   end

% end

//===----------------------------------------------------------------------===//
// map()
//===----------------------------------------------------------------------===//

struct MapTest {
  let expected: [Int32]
  let sequence: [Int]
  let transform: (Int) -> Int32
  let loc: SourceLoc

  init(
    _ expected: [Int32],
    _ sequence: [Int],
    _ transform: (Int) -> Int32,
    file: String = __FILE__, line: UWord = __LINE__
  ) {
    self.expected = expected
    self.sequence = sequence
    self.transform = transform
    self.loc = SourceLoc(file, line, comment: "test data")
  }
}

let mapTests = [
  MapTest(
    [], [],
    { (x: Int) -> Int32 in expectUnreachable(); return 0xffff }),

  MapTest([ 101 ], [ 1 ], { (x: Int) -> Int32 in x + 100 }),
  MapTest([ 101, 102 ], [ 1, 2 ], { (x: Int) -> Int32 in x + 100 }),
  MapTest([ 101, 102, 103 ], [ 1, 2, 3 ], { (x: Int) -> Int32 in x + 100 }),
]

SequenceTypeAlgorithms.test("map/SequenceType") {
  expectEqual(0, LifetimeTracked.instances)
  for test in mapTests {
    for underestimateCountBehavior in [
      UnderestimateCountBehavior.Overestimate,
      UnderestimateCountBehavior.Value(0)
    ] {
      let s = MinimalSequence<OpaqueValue<Int>>(
        test.sequence.map { OpaqueValue($0) },
        underestimatedCount: underestimateCountBehavior)
      let closureLifetimeTracker = LifetimeTracked(0)
      expectEqual(1, LifetimeTracked.instances)
      var timesClosureWasCalled = 0
      var result = s._prext_map {
        (element: OpaqueValue<Int>) -> OpaqueValue<Int32> in
        _blackHole(closureLifetimeTracker)
        ++timesClosureWasCalled
        return OpaqueValue(Int32(test.transform(element.value)))
      }
      expectType([OpaqueValue<Int32>].self, &result)
      expectEqual(test.expected, result._prext_map { $0.value })
      expectEqual([], s._prext_map { $0.value }) { "sequence should be consumed" }
      expectEqual(test.sequence.count, timesClosureWasCalled) {
        "map() should be eager and should only call its predicate once per element"
      }
      // FIXME: <rdar://problem/19810841> Reserve capacity when running map() over a SequenceType
      // expectLE(s.underestimatedCount, result.capacity) {
      //   "map() should reserve capacity"
      // }
    }
  }
  expectEqual(0, LifetimeTracked.instances)
}

SequenceTypeAlgorithms.test("map/CollectionType") {
  expectEqual(0, LifetimeTracked.instances)
  for test in mapTests {
    for underestimateCountBehavior in [
      UnderestimateCountBehavior.Precise,
      UnderestimateCountBehavior.Value(0)
    ] {
      let s = MinimalForwardCollection<OpaqueValue<Int>>(
        test.sequence.map { OpaqueValue($0) },
        underestimatedCount: underestimateCountBehavior)
      let closureLifetimeTracker = LifetimeTracked(0)
      expectEqual(1, LifetimeTracked.instances)
      var timesClosureWasCalled = 0
      var result = s._prext_map {
        (element: OpaqueValue<Int>) -> OpaqueValue<Int32> in
        _blackHole(closureLifetimeTracker)
        ++timesClosureWasCalled
        return OpaqueValue(Int32(test.transform(element.value)))
      }
      expectType([OpaqueValue<Int32>].self, &result)
      expectEqual(test.expected, result._prext_map { $0.value })
      expectEqual(test.sequence, s._prext_map { $0.value }) {
        "collection should not be consumed"
      }
      expectEqual(test.sequence.count, timesClosureWasCalled) {
        "map() should be eager and should only call its predicate once per element"
      }
      expectGE(result.count + 3, result.capacity) {
        "map() should use the precise element count"
      }
    }
  }
  expectEqual(0, LifetimeTracked.instances)
}

//===----------------------------------------------------------------------===//
// flatMap()
//===----------------------------------------------------------------------===//

struct FlatMapTest {
  let expected: [Int32]
  let sequence: [Int]
  let transform: (Int) -> [Int32]
  let loc: SourceLoc

  init(
    _ expected: [Int32],
    _ sequence: [Int],
    _ transform: (Int) -> [Int32],
    file: String = __FILE__, line: UWord = __LINE__
  ) {
    self.expected = expected
    self.sequence = sequence
    self.transform = transform
    self.loc = SourceLoc(file, line, comment: "test data")
  }
}

func flatMapTransformation(x: Int) -> [Int32] {
  let repetitions = x / 10
  let identity = x % 10
  return (1..<(repetitions+1)).map { $0 * 10 + identity }
}

let flatMapTests = [
  FlatMapTest(
    [], [],
    { (x: Int) -> [Int32] in expectUnreachable(); return [ 0xffff ] }),

  FlatMapTest([], [ 1 ], { (x: Int) -> [Int32] in [] }),
  FlatMapTest([], [ 1, 2 ], { (x: Int) -> [Int32] in [] }),
  FlatMapTest([], [ 1, 2, 3 ], { (x: Int) -> [Int32] in [] }),

  FlatMapTest([ 101 ], [ 1 ], { (x: Int) -> [Int32] in [ x + 100 ] }),
  FlatMapTest([ 101, 102 ], [ 1, 2 ], { (x: Int) -> [Int32] in [ x + 100 ] }),
  FlatMapTest(
    [ 101, 102, 103 ], [ 1, 2, 3 ], { (x: Int) -> [Int32] in [ x + 100 ] }),

  FlatMapTest(
    [ 101, 201 ], [ 1 ],
    { (x: Int) -> [Int32] in [ x + 100, x + 200 ] }),
  FlatMapTest(
    [ 101, 201, 102, 202 ], [ 1, 2 ],
    { (x: Int) -> [Int32] in [ x + 100, x + 200 ] }),
  FlatMapTest(
    [ 101, 201, 102, 202, 103, 203 ], [ 1, 2, 3 ],
    { (x: Int) -> [Int32] in [ x + 100, x + 200 ] }),

  FlatMapTest([ 11, 15 ], [ 11, 2, 3, 4, 15 ], flatMapTransformation),
  FlatMapTest([ 12, 13, 23 ], [ 1, 12, 23 ], flatMapTransformation),
  FlatMapTest(
    [ 11, 21, 13, 23, 33, 14 ], [ 21, 2, 33, 14 ], flatMapTransformation),
]

SequenceTypeAlgorithms.test("flatMap/SequenceType") {
  for test in flatMapTests {
    for underestimateCountBehavior in [
      UnderestimateCountBehavior.Overestimate,
      UnderestimateCountBehavior.Value(0)
    ] {
      let s = MinimalSequence<OpaqueValue<Int>>(
        test.sequence.map { OpaqueValue($0) },
        underestimatedCount: underestimateCountBehavior)
      var timesClosureWasCalled = 0
      var result = s._prext_flatMap {
        (element: OpaqueValue<Int>) -> MinimalSequence<OpaqueValue<Int32>> in
        ++timesClosureWasCalled
        return MinimalSequence<OpaqueValue<Int32>>(
          test.transform(element.value).map { OpaqueValue(Int32($0)) })
      }
      expectType([OpaqueValue<Int32>].self, &result)
      expectEqual(
        test.expected, result._prext_map { $0.value },
        stackTrace: test.loc.withCurrentLoc())
      expectEqual([], s._prext_map { $0.value }) { "sequence should be consumed" }
      expectEqual(test.sequence.count, timesClosureWasCalled) {
        "map() should be eager and should only call its predicate once per element"
      }
      expectGE(2 * count(result), result.capacity) {
        "flatMap() should not reserve capacity"
      }
    }
  }
}

struct FlatMapToOptionalTest {
  let expected: [Int32]
  let sequence: [Int]
  let transform: (Int) -> Int32?
  let loc: SourceLoc

  init(
    _ expected: [Int32],
    _ sequence: [Int],
    _ transform: (Int) -> Int32?,
    file: String = __FILE__, line: UWord = __LINE__
  ) {
    self.expected = expected
    self.sequence = sequence
    self.transform = transform
    self.loc = SourceLoc(file, line, comment: "test data")
  }
}

let flatMapToOptionalTests = [
  FlatMapToOptionalTest(
    [], [],
    { (x: Int) -> Int32? in expectUnreachable(); return 0xffff }),

  FlatMapToOptionalTest([], [ 1 ], { (x: Int) -> Int32? in nil }),
  FlatMapToOptionalTest([], [ 1, 2 ], { (x: Int) -> Int32? in nil }),
  FlatMapToOptionalTest([], [ 1, 2, 3 ], { (x: Int) -> Int32? in nil }),

  FlatMapToOptionalTest(
    [ 1 ], [ 1 ],
    { (x: Int) -> Int32? in x > 10 ? nil : Int32(x) }),
  FlatMapToOptionalTest(
    [ 2 ], [ 11, 2, 13, 14 ],
    { (x: Int) -> Int32? in x > 10 ? nil : Int32(x) }),
  FlatMapToOptionalTest(
    [ 1, 4 ], [ 1, 12, 13, 4 ],
    { (x: Int) -> Int32? in x > 10 ? nil : Int32(x) }),
  FlatMapToOptionalTest(
    [ 1, 2, 3 ], [ 1, 2, 3 ],
    { (x: Int) -> Int32? in x > 10 ? nil : Int32(x) }),
]

SequenceTypeAlgorithms.test("flatMap/SequenceType/TransformProducesOptional") {
  for test in flatMapToOptionalTests {
    for underestimateCountBehavior in [
      UnderestimateCountBehavior.Overestimate,
      UnderestimateCountBehavior.Value(0)
    ] {
      let s = MinimalSequence<OpaqueValue<Int>>(
        test.sequence.map { OpaqueValue($0) },
        underestimatedCount: underestimateCountBehavior)
      var timesClosureWasCalled = 0
      var result = s._prext_flatMap {
        (element: OpaqueValue<Int>) -> OpaqueValue<Int32>? in
        ++timesClosureWasCalled
        return test.transform(element.value).map { OpaqueValue(Int32($0)) }
      }
      expectType([OpaqueValue<Int32>].self, &result)
      expectEqual(
        test.expected, result._prext_map { $0.value },
        stackTrace: test.loc.withCurrentLoc())
      expectEqual([], s._prext_map { $0.value }) { "sequence should be consumed" }
      expectEqual(test.sequence.count, timesClosureWasCalled) {
        "flatMap() should be eager and should only call its predicate once per element"
      }
      expectGE(2 * count(result), result.capacity) {
        "flatMap() should not reserve capacity"
      }
    }
  }
}

//===----------------------------------------------------------------------===//
// zip()
//===----------------------------------------------------------------------===//

struct ZipTest {
  let expected: [(Int, Int32)]
  let sequence: [Int]
  let other: [Int32]
  let expectedLeftoverSequence: [Int]
  let expectedLeftoverOther: [Int32]
  let loc: SourceLoc

  init(
    _ expected: [(Int, Int32)],
    sequences sequence: [Int],
    _ other: [Int32],
    leftovers expectedLeftoverSequence: [Int],
    _ expectedLeftoverOther: [Int32],
    file: String = __FILE__, line: UWord = __LINE__
  ) {
    self.expected = expected
    self.sequence = sequence
    self.other = other
    self.expectedLeftoverSequence = expectedLeftoverSequence
    self.expectedLeftoverOther = expectedLeftoverOther
    self.loc = SourceLoc(file, line, comment: "test data")
  }
}

let zipTests = [
  ZipTest([], sequences: [], [], leftovers: [], []),
  ZipTest([], sequences: [], [ 1 ], leftovers: [], [ 1 ]),
  ZipTest([], sequences: [], [ 1, 2 ], leftovers: [], [ 1, 2 ]),
  ZipTest([], sequences: [], [ 1, 2, 3 ], leftovers: [], [ 1, 2, 3 ]),

  ZipTest([], sequences: [ 10 ], [], leftovers: [], []),
  ZipTest([ (10, 1) ], sequences: [ 10 ], [ 1 ], leftovers: [], []),
  ZipTest([ (10, 1) ], sequences: [ 10 ], [ 1, 2 ], leftovers: [], [ 2 ]),
  ZipTest([ (10, 1) ], sequences: [ 10 ], [ 1, 2, 3 ], leftovers: [], [ 2, 3 ]),

  ZipTest(
    [],
    sequences: [ 10, 20 ], [],
    leftovers: [ 20 ], []),
  ZipTest(
    [ (10, 1) ],
    sequences: [ 10, 20 ], [ 1 ],
    leftovers: [], []),
  ZipTest(
    [ (10, 1), (20, 2) ],
    sequences: [ 10, 20 ], [ 1, 2 ],
    leftovers: [], []),
  ZipTest(
    [ (10, 1), (20, 2) ],
    sequences: [ 10, 20 ], [ 1, 2, 3 ],
    leftovers: [], [ 3 ]),

  ZipTest(
    [],
    sequences: [ 10, 20, 30 ], [],
    leftovers: [ 20, 30 ], []),
  ZipTest(
    [ (10, 1) ],
    sequences: [ 10, 20, 30 ], [ 1 ],
    leftovers: [ 30 ], []),
  ZipTest(
    [ (10, 1), (20, 2) ],
    sequences: [ 10, 20, 30 ], [ 1, 2 ],
    leftovers: [], []),
  ZipTest(
    [ (10, 1), (20, 2), (30, 3) ],
    sequences: [ 10, 20, 30 ], [ 1, 2, 3 ],
    leftovers: [], []),
]

SequenceTypeAlgorithms.test("zip") {
  typealias Element = (OpaqueValue<Int>, OpaqueValue<Int32>)
  func compareElements(lhs: Element, rhs: Element) -> Bool {
    return lhs.0.value == rhs.0.value && lhs.1.value == rhs.1.value
  }

  for test in zipTests {
    let s = MinimalSequence<OpaqueValue<Int>>(
      test.sequence.map { OpaqueValue($0) })
    let other = MinimalSequence<OpaqueValue<Int32>>(
      test.other.map { OpaqueValue($0) })
    var result = s._prext_zip(other)
    expectType(
      Zip2<MinimalSequence<OpaqueValue<Int>>, MinimalSequence<OpaqueValue<Int32>>>.self,
      &result)

    // Check for expected result and check the Zip2 SequenceType conformance.
    checkSequence(
      test.expected._prext_map { (OpaqueValue($0), OpaqueValue($1)) },
      result,
      compareElements,
      test.loc.withCurrentLoc())
    // Check leftovers *after* doing checkSequence(), not before, to ensure
    // that checkSequence() didn't force us to consume more elements than
    // needed.
    expectEqual(
      test.expectedLeftoverSequence, s._prext_map { $0.value },
      stackTrace: test.loc.withCurrentLoc())
    expectEqual(
      test.expectedLeftoverOther, other._prext_map { $0.value },
      stackTrace: test.loc.withCurrentLoc())
  }
}

//===----------------------------------------------------------------------===//
// underestimateCount()
//===----------------------------------------------------------------------===//

func callGenericUnderestimatedCount<S : SequenceType>(s: S) -> Int {
  return s._prext_underestimateCount()
}

struct SequenceWithDefaultUnderestimateCount : SequenceType {
  init() {}

  func generate() -> MinimalSequence<OpaqueValue<Int>>.Generator {
    expectUnreachable()
    return MinimalSequence(
      [ 1, 2, 3 ]._prext_map { OpaqueValue($0) }
    ).generate()
  }
}

SequenceTypeAlgorithms.test("underestimateCount/SequenceType/DefaultImplementation") {
  let s = SequenceWithDefaultUnderestimateCount()
  expectEqual(0, callGenericUnderestimatedCount(s))
}

struct SequenceWithCustomUnderestimateCount : SequenceType {
  init(underestimatedCount: Int) {
    self._underestimatedCount = underestimatedCount
  }

  func generate() -> MinimalSequence<OpaqueValue<Int>>.Generator {
    expectUnreachable()
    return MinimalSequence(
      [ 0xffff, 0xffff, 0xffff ]._prext_map { OpaqueValue($0) }
    ).generate()
  }

  func _prext_underestimateCount() -> Int {
    return _underestimatedCount
  }

  let _underestimatedCount: Int
}

SequenceTypeAlgorithms.test("underestimateCount/SequenceType/CustomImplementation") {
  if true {
    let s = SequenceWithCustomUnderestimateCount(underestimatedCount: 5)
    expectEqual(5, callGenericUnderestimatedCount(s))
  }
  if true {
    let s = SequenceWithCustomUnderestimateCount(underestimatedCount: 42)
    expectEqual(42, callGenericUnderestimatedCount(s))
  }
}

struct CollectionWithDefaultUnderestimateCount : CollectionType {
  init(count: Int) {
    self._count = count
  }

  func generate() -> MinimalGenerator<OpaqueValue<Int>> {
    expectUnreachable()
    return MinimalGenerator([])
  }

  var startIndex: MinimalForwardIndex {
    return MinimalForwardIndex(position: 0, startIndex: 0, endIndex: _count)
  }

  var endIndex: MinimalForwardIndex {
    return MinimalForwardIndex(
      position: _count, startIndex: 0, endIndex: _count)
  }

  subscript(i: MinimalForwardIndex) -> OpaqueValue<Int> {
    expectUnreachable()
    return OpaqueValue(0xffff)
  }

  var _count: Int
}

SequenceTypeAlgorithms.test("underestimateCount/CollectionType/DefaultImplementation") {
  if true {
    let s = CollectionWithDefaultUnderestimateCount(count: 0)
    expectEqual(0, callGenericUnderestimatedCount(s))
  }
  if true {
    let s = CollectionWithDefaultUnderestimateCount(count: 5)
    expectEqual(5, callGenericUnderestimatedCount(s))
  }
}

struct CollectionWithCustomUnderestimateCount : CollectionType {
  init(underestimatedCount: Int) {
    self._underestimatedCount = underestimatedCount
  }

  func generate() -> MinimalGenerator<OpaqueValue<Int>> {
    expectUnreachable()
    return MinimalGenerator([])
  }

  var startIndex: MinimalForwardIndex {
    expectUnreachable()
    return MinimalForwardIndex(position: 0, startIndex: 0, endIndex: 0xffff)
  }

  var endIndex: MinimalForwardIndex {
    expectUnreachable()
    return MinimalForwardIndex(
      position: 0xffff, startIndex: 0, endIndex: 0xffff)
  }

  subscript(i: MinimalForwardIndex) -> OpaqueValue<Int> {
    expectUnreachable()
    return OpaqueValue(0xffff)
  }

  func _prext_underestimateCount() -> Int {
    return _underestimatedCount
  }

  let _underestimatedCount: Int
}

SequenceTypeAlgorithms.test("underestimateCount/CollectionType/CustomImplementation") {
  if true {
    let s = CollectionWithCustomUnderestimateCount(underestimatedCount: 0)
    expectEqual(0, callGenericUnderestimatedCount(s))
  }
  if true {
    let s = CollectionWithCustomUnderestimateCount(underestimatedCount: 5)
    expectEqual(5, callGenericUnderestimatedCount(s))
  }
}


//===----------------------------------------------------------------------===//
// isEmpty
//===----------------------------------------------------------------------===//

SequenceTypeAlgorithms.test("isEmpty") {
  if true {
    let s = MinimalForwardCollection<OpaqueValue<Int>>([])
    expectTrue(s._prext_isEmpty)
  }
  if true {
    let s = MinimalForwardCollection<OpaqueValue<Int>>(
      [ 1 ]._prext_map { OpaqueValue($0) })
    expectFalse(s._prext_isEmpty)
  }
}

//===----------------------------------------------------------------------===//
// first
//===----------------------------------------------------------------------===//

SequenceTypeAlgorithms.test("first") {
  if true {
    let s = MinimalForwardCollection<OpaqueValue<Int>>([])
    expectEmpty(s._prext_first)
  }
  if true {
    let s = MinimalForwardCollection<OpaqueValue<Int>>([
      OpaqueValue<Int>(1, identity: 10),
      OpaqueValue<Int>(2, identity: 20)
    ])
    if let result? = s._prext_first {
      expectEqual(1, result.value)
      expectEqual(10, result.identity)
    } else {
      expectUnreachable()
    }
  }
}

//===----------------------------------------------------------------------===//
// find()
//===----------------------------------------------------------------------===//

func callStaticFind(
  collection: MinimalForwardCollection<MinimalEquatableValue>,
  element: MinimalEquatableValue
) -> MinimalForwardCollection<MinimalEquatableValue>.Index? {
  return collection._prext_find(element)
}

func callGenericFind<
  C : CollectionType where C.Generator.Element : Equatable
>(collection: C, element: C.Generator.Element) -> C.Index? {
  return collection._prext_find(element)
}

% for dispatch in [ 'Static', 'Generic' ]:

SequenceTypeAlgorithms.test("find/WhereElementIsEquatable/${dispatch}") {
  for test in findTests {
    let s = MinimalForwardCollection<MinimalEquatableValue>(
      test.sequence.map { MinimalEquatableValue($0) })
    expectEqual(
      test.expected,
      call${dispatch}Find(s, MinimalEquatableValue(test.element))
        .map { $0.position },
      stackTrace: test.loc.withCurrentLoc())
  }
}

% end

SequenceTypeAlgorithms.test("find/Predicate") {
  for test in findTests {
    let s = MinimalForwardCollection<MinimalEquatableValue>(
      test.sequence.map { MinimalEquatableValue($0) })
    expectEqual(
      test.expected,
      s._prext_find { $0.value == test.element }
        .map { $0.position },
      stackTrace: test.loc.withCurrentLoc())
  }
}

//===----------------------------------------------------------------------===//
// indices()
//===----------------------------------------------------------------------===//

SequenceTypeAlgorithms.test("indices") {
  if true {
    let s = MinimalForwardCollection<OpaqueValue<Int>>([])
    let indices = s._prext_indices
    expectEqual(s.startIndex, indices.startIndex)
    expectEqual(s.endIndex, indices.endIndex)
  }
  if true {
    let s = MinimalForwardCollection<OpaqueValue<Int>>([
      OpaqueValue<Int>(1, identity: 10),
      OpaqueValue<Int>(2, identity: 20)
    ])
    let indices = s._prext_indices
    expectEqual(s.startIndex, indices.startIndex)
    expectEqual(s.endIndex, indices.endIndex)
  }
}

runAllTests()