| //===--- Stride.swift.gyb - Components for stride(...) iteration ----------===// |
| // |
| // 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 |
| // |
| //===----------------------------------------------------------------------===// |
| |
| /// Conforming types are notionally continuous, one-dimensional |
| /// values that can be offset and measured. |
| /// |
| /// - Important: The `Strideable` protocol provides default implementations for |
| /// the equal-to (`==`) and less-than (`<`) operators that depend on the |
| /// `Stride` type's implementations. If a type conforming to `Strideable` |
| /// is its own `Stride` type, it must provide concrete implementations of |
| /// the two operators to avoid infinite recursion. |
| public protocol Strideable : Comparable { |
| /// A type that represents the distance between two values of `Self`. |
| associatedtype Stride : SignedNumeric, Comparable |
| |
| /// Returns a stride `x` such that `self.advanced(by: x)` approximates |
| /// `other`. |
| /// |
| /// If `Stride` conforms to `Integer`, then `self.advanced(by: x) == other`. |
| /// |
| /// - Complexity: O(1). |
| func distance(to other: Self) -> Stride |
| |
| /// Returns a `Self` `x` such that `self.distance(to: x)` approximates `n`. |
| /// |
| /// If `Stride` conforms to `Integer`, then `self.distance(to: x) == n`. |
| /// |
| /// - Complexity: O(1). |
| func advanced(by n: Stride) -> Self |
| |
| /// `_step` is an implementation detail of Strideable; do not use it directly. |
| static func _step( |
| after current: (index: Int?, value: Self), |
| from start: Self, by distance: Self.Stride |
| ) -> (index: Int?, value: Self) |
| |
| associatedtype _DisabledRangeIndex = Never |
| } |
| |
| extension Strideable { |
| @_inlineable |
| public static func < (x: Self, y: Self) -> Bool { |
| return x.distance(to: y) > 0 |
| } |
| |
| @_inlineable |
| public static func == (x: Self, y: Self) -> Bool { |
| return x.distance(to: y) == 0 |
| } |
| } |
| |
| //===----------------------------------------------------------------------===// |
| |
| %{ |
| # Strideable used to provide + and - unconditionally. With the updated |
| # collection indexing model of Swift 3 this became unnecessary for integer |
| # types, and was deprecated, as it was a way to write mixed-type arithmetic |
| # expressions, that are otherwise are not allowed. |
| }% |
| % for Base, VersionInfo in [ |
| % ('Strideable where Self : _Pointer', None), |
| % ('Strideable', 'deprecated: 3, obsoleted: 4'), |
| % ]: |
| % Availability = '@available(swift, %s, message: "Please use explicit type conversions or Strideable methods for mixed-type arithmetics.")' % (VersionInfo) if VersionInfo else '' |
| |
| extension ${Base} { |
| @_inlineable // FIXME(sil-serialize-all) |
| @_transparent |
| ${Availability} |
| public static func + (lhs: Self, rhs: Self.Stride) -> Self { |
| return lhs.advanced(by: rhs) |
| } |
| |
| @_inlineable // FIXME(sil-serialize-all) |
| @_transparent |
| ${Availability} |
| public static func + (lhs: Self.Stride, rhs: Self) -> Self { |
| return rhs.advanced(by: lhs) |
| } |
| |
| @_inlineable // FIXME(sil-serialize-all) |
| @_transparent |
| ${Availability} |
| public static func - (lhs: Self, rhs: Self.Stride) -> Self { |
| return lhs.advanced(by: -rhs) |
| } |
| |
| @_inlineable // FIXME(sil-serialize-all) |
| @_transparent |
| ${Availability} |
| public static func - (lhs: Self, rhs: Self) -> Self.Stride { |
| return rhs.distance(to: lhs) |
| } |
| |
| @_inlineable // FIXME(sil-serialize-all) |
| @_transparent |
| ${Availability} |
| public static func += (lhs: inout Self, rhs: Self.Stride) { |
| lhs = lhs.advanced(by: rhs) |
| } |
| |
| @_inlineable // FIXME(sil-serialize-all) |
| @_transparent |
| ${Availability} |
| public static func -= (lhs: inout Self, rhs: Self.Stride) { |
| lhs = lhs.advanced(by: -rhs) |
| } |
| } |
| |
| % end |
| |
| //===----------------------------------------------------------------------===// |
| |
| extension Strideable { |
| @_inlineable |
| public static func _step( |
| after current: (index: Int?, value: Self), |
| from start: Self, by distance: Self.Stride |
| ) -> (index: Int?, value: Self) { |
| return (nil, current.value.advanced(by: distance)) |
| } |
| } |
| |
| extension Strideable where Stride : FloatingPoint { |
| @_inlineable |
| public static func _step( |
| after current: (index: Int?, value: Self), |
| from start: Self, by distance: Self.Stride |
| ) -> (index: Int?, value: Self) { |
| if let i = current.index { |
| // When Stride is a floating-point type, we should avoid accumulating |
| // rounding error from repeated addition. |
| return (i + 1, start.advanced(by: Stride(i + 1) * distance)) |
| } |
| return (nil, current.value.advanced(by: distance)) |
| } |
| } |
| |
| extension Strideable where Self : FloatingPoint, Self == Stride { |
| @_inlineable |
| public static func _step( |
| after current: (index: Int?, value: Self), |
| from start: Self, by distance: Self.Stride |
| ) -> (index: Int?, value: Self) { |
| if let i = current.index { |
| // When both Self and Stride are the same floating-point type, we should |
| // take advantage of fused multiply-add (where supported) to eliminate |
| // intermediate rounding error. |
| return (i + 1, start.addingProduct(Stride(i + 1), distance)) |
| } |
| return (nil, current.value.advanced(by: distance)) |
| } |
| } |
| |
| /// An iterator for `StrideTo<Element>`. |
| @_fixed_layout |
| public struct StrideToIterator<Element : Strideable> { |
| @_versioned |
| internal let _start: Element |
| |
| @_versioned |
| internal let _end: Element |
| |
| @_versioned |
| internal let _stride: Element.Stride |
| |
| @_versioned |
| internal var _current: (index: Int?, value: Element) |
| |
| @_inlineable |
| @_versioned |
| internal init(_start: Element, end: Element, stride: Element.Stride) { |
| self._start = _start |
| _end = end |
| _stride = stride |
| _current = (0, _start) |
| } |
| } |
| |
| extension StrideToIterator: IteratorProtocol { |
| /// Advances to the next element and returns it, or `nil` if no next element |
| /// exists. |
| /// |
| /// Once `nil` has been returned, all subsequent calls return `nil`. |
| @_inlineable |
| public mutating func next() -> Element? { |
| let result = _current.value |
| if _stride > 0 ? result >= _end : result <= _end { |
| return nil |
| } |
| _current = Element._step(after: _current, from: _start, by: _stride) |
| return result |
| } |
| } |
| |
| /// A `Sequence` of values formed by striding over a half-open interval. |
| // FIXME: should really be a Collection, as it is multipass |
| @_fixed_layout |
| public struct StrideTo<Element : Strideable> { |
| @_versioned |
| internal let _start: Element |
| |
| @_versioned |
| internal let _end: Element |
| |
| @_versioned |
| internal let _stride: Element.Stride |
| |
| @_inlineable |
| @_versioned |
| internal init(_start: Element, end: Element, stride: Element.Stride) { |
| _precondition(stride != 0, "Stride size must not be zero") |
| // At start, striding away from end is allowed; it just makes for an |
| // already-empty Sequence. |
| self._start = _start |
| self._end = end |
| self._stride = stride |
| } |
| } |
| |
| extension StrideTo: Sequence { |
| /// Returns an iterator over the elements of this sequence. |
| /// |
| /// - Complexity: O(1). |
| @_inlineable |
| public func makeIterator() -> StrideToIterator<Element> { |
| return StrideToIterator(_start: _start, end: _end, stride: _stride) |
| } |
| |
| // FIXME(conditional-conformances): this is O(N) instead of O(1), leaving it |
| // here until a proper Collection conformance is possible |
| @_inlineable |
| public var underestimatedCount: Int { |
| var it = self.makeIterator() |
| var count = 0 |
| while it.next() != nil { |
| count += 1 |
| } |
| return count |
| } |
| |
| @_inlineable |
| public func _preprocessingPass<R>( |
| _ preprocess: () throws -> R |
| ) rethrows -> R? { |
| return try preprocess() |
| } |
| |
| @_inlineable |
| public func _customContainsEquatableElement( |
| _ element: Element |
| ) -> Bool? { |
| if element < _start || _end <= element { |
| return false |
| } |
| return nil |
| } |
| } |
| |
| extension StrideTo: CustomReflectable { |
| @_inlineable // FIXME(sil-serialize-all) |
| public var customMirror: Mirror { |
| return Mirror(self, children: ["from": _start, "to": _end, "by": _stride]) |
| } |
| } |
| |
| // FIXME(conditional-conformances): This does not yet compile (SR-6474). |
| #if false |
| extension StrideTo : RandomAccessCollection |
| where Element.Stride : BinaryInteger { |
| public typealias Index = Int |
| public typealias SubSequence = Slice<StrideTo<Element>> |
| public typealias Indices = CountableRange<Int> |
| |
| @_inlineable |
| public var startIndex: Index { return 0 } |
| |
| @_inlineable |
| public var endIndex: Index { return count } |
| |
| @_inlineable |
| public var count: Int { |
| let distance = _start.distance(to: _end) |
| guard distance != 0 && (distance < 0) == (_stride < 0) else { return 0 } |
| return Int((distance - 1) / _stride) + 1 |
| } |
| |
| public subscript(position: Index) -> Element { |
| _failEarlyRangeCheck(position, bounds: startIndex..<endIndex) |
| return _start.advanced(by: Element.Stride(position) * _stride) |
| } |
| |
| public subscript(bounds: Range<Index>) -> Slice<StrideTo<Element>> { |
| _failEarlyRangeCheck(bounds, bounds: startIndex ..< endIndex) |
| return Slice(base: self, bounds: bounds) |
| } |
| |
| @_inlineable |
| public func index(before i: Index) -> Index { |
| _failEarlyRangeCheck(i, bounds: startIndex + 1...endIndex) |
| return i - 1 |
| } |
| |
| @_inlineable |
| public func index(after i: Index) -> Index { |
| _failEarlyRangeCheck(i, bounds: startIndex - 1..<endIndex) |
| return i + 1 |
| } |
| } |
| #endif |
| |
| /// Returns the sequence of values (`self`, `self + stride`, `self + |
| /// 2 * stride`, ... *last*) where *last* is the last value in the |
| /// progression that is less than `end`. |
| @_inlineable |
| public func stride<T>( |
| from start: T, to end: T, by stride: T.Stride |
| ) -> StrideTo<T> { |
| return StrideTo(_start: start, end: end, stride: stride) |
| } |
| |
| /// An iterator for `StrideThrough<Element>`. |
| @_fixed_layout |
| public struct StrideThroughIterator<Element : Strideable> { |
| @_versioned |
| internal let _start: Element |
| |
| @_versioned |
| internal let _end: Element |
| |
| @_versioned |
| internal let _stride: Element.Stride |
| |
| @_versioned |
| internal var _current: (index: Int?, value: Element) |
| |
| @_versioned |
| internal var _didReturnEnd: Bool = false |
| |
| @_inlineable |
| @_versioned |
| internal init(_start: Element, end: Element, stride: Element.Stride) { |
| self._start = _start |
| _end = end |
| _stride = stride |
| _current = (0, _start) |
| } |
| } |
| |
| extension StrideThroughIterator: IteratorProtocol { |
| /// Advances to the next element and returns it, or `nil` if no next element |
| /// exists. |
| /// |
| /// Once `nil` has been returned, all subsequent calls return `nil`. |
| @_inlineable |
| public mutating func next() -> Element? { |
| let result = _current.value |
| if _stride > 0 ? result >= _end : result <= _end { |
| // This check is needed because if we just changed the above operators |
| // to > and <, respectively, we might advance current past the end |
| // and throw it out of bounds (e.g. above Int.max) unnecessarily. |
| if result == _end && !_didReturnEnd { |
| _didReturnEnd = true |
| return result |
| } |
| return nil |
| } |
| _current = Element._step(after: _current, from: _start, by: _stride) |
| return result |
| } |
| } |
| |
| /// A `Sequence` of values formed by striding over a closed interval. |
| // FIXME: should really be a CollectionType, as it is multipass |
| @_fixed_layout |
| public struct StrideThrough<Element: Strideable> { |
| @_versioned |
| internal let _start: Element |
| @_versioned |
| internal let _end: Element |
| @_versioned |
| internal let _stride: Element.Stride |
| |
| @_inlineable |
| @_versioned |
| internal init(_start: Element, end: Element, stride: Element.Stride) { |
| _precondition(stride != 0, "Stride size must not be zero") |
| self._start = _start |
| self._end = end |
| self._stride = stride |
| } |
| } |
| |
| extension StrideThrough: Sequence { |
| /// Returns an iterator over the elements of this sequence. |
| /// |
| /// - Complexity: O(1). |
| @_inlineable |
| public func makeIterator() -> StrideThroughIterator<Element> { |
| return StrideThroughIterator(_start: _start, end: _end, stride: _stride) |
| } |
| |
| // FIXME(conditional-conformances): this is O(N) instead of O(1), leaving it |
| // here until a proper Collection conformance is possible |
| @_inlineable |
| public var underestimatedCount: Int { |
| var it = self.makeIterator() |
| var count = 0 |
| while it.next() != nil { |
| count += 1 |
| } |
| return count |
| } |
| |
| @_inlineable |
| public func _preprocessingPass<R>( |
| _ preprocess: () throws -> R |
| ) rethrows -> R? { |
| return try preprocess() |
| } |
| |
| @_inlineable |
| public func _customContainsEquatableElement( |
| _ element: Element |
| ) -> Bool? { |
| if element < _start || _end < element { |
| return false |
| } |
| return nil |
| } |
| } |
| |
| extension StrideThrough: CustomReflectable { |
| @_inlineable // FIXME(sil-serialize-all) |
| public var customMirror: Mirror { |
| return Mirror(self, |
| children: ["from": _start, "through": _end, "by": _stride]) |
| } |
| } |
| |
| // FIXME(conditional-conformances): This does not yet compile (SR-6474). |
| #if false |
| extension StrideThrough : RandomAccessCollection |
| where Element.Stride : BinaryInteger { |
| public typealias Index = ClosedRangeIndex<Int> |
| public typealias IndexDistance = Int |
| public typealias SubSequence = Slice<StrideThrough<Element>> |
| |
| @_inlineable |
| public var startIndex: Index { |
| let distance = _start.distance(to: _end) |
| return distance == 0 || (distance < 0) == (_stride < 0) |
| ? ClosedRangeIndex(0) |
| : ClosedRangeIndex() |
| } |
| |
| @_inlineable |
| public var endIndex: Index { return ClosedRangeIndex() } |
| |
| @_inlineable |
| public var count: Int { |
| let distance = _start.distance(to: _end) |
| guard distance != 0 else { return 1 } |
| guard (distance < 0) == (_stride < 0) else { return 0 } |
| return Int(distance / _stride) + 1 |
| } |
| |
| public subscript(position: Index) -> Element { |
| let offset = Element.Stride(position._dereferenced) * _stride |
| return _start.advanced(by: offset) |
| } |
| |
| public subscript(bounds: Range<Index>) -> Slice<StrideThrough<Element>> { |
| return Slice(base: self, bounds: bounds) |
| } |
| |
| @_inlineable |
| public func index(before i: Index) -> Index { |
| switch i._value { |
| case .inRange(let n): |
| _precondition(n > 0, "Incrementing past start index") |
| return ClosedRangeIndex(n - 1) |
| case .pastEnd: |
| _precondition(_end >= _start, "Incrementing past start index") |
| return ClosedRangeIndex(count - 1) |
| } |
| } |
| |
| @_inlineable |
| public func index(after i: Index) -> Index { |
| switch i._value { |
| case .inRange(let n): |
| return n == (count - 1) |
| ? ClosedRangeIndex() |
| : ClosedRangeIndex(n + 1) |
| case .pastEnd: |
| _preconditionFailure("Incrementing past end index") |
| } |
| } |
| } |
| #endif |
| |
| /// Returns the sequence of values (`self`, `self + stride`, `self + |
| /// 2 * stride`, ... *last*) where *last* is the last value in the |
| /// progression less than or equal to `end`. |
| /// |
| /// - Note: There is no guarantee that `end` is an element of the sequence. |
| @_inlineable |
| public func stride<T>( |
| from start: T, through end: T, by stride: T.Stride |
| ) -> StrideThrough<T> { |
| return StrideThrough(_start: start, end: end, stride: stride) |
| } |