| //===--- 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 |
| // |
| //===----------------------------------------------------------------------===// |
| |
| // FIXME(ABI)#69 (Overload Resolution): Remove `_Strideable`. |
| // WORKAROUND rdar://25214598 - should be: |
| // protocol Strideable : Comparable {...} |
| |
| % for Self in ['_Strideable', 'Strideable']: |
| |
| %{ |
| Conformance = ( |
| 'Equatable' if Self == '_Strideable' else '_Strideable, Comparable' |
| ) |
| }% |
| /// 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 ${Self} : ${Conformance} { |
| % if Self == '_Strideable': |
| /// A type that represents the distance between two values of `Self`. |
| associatedtype Stride : SignedNumeric, Comparable |
| % end |
| |
| /// 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 = _DisabledRangeIndex_ |
| } |
| |
| % end |
| |
| extension Strideable where Stride == Self { |
| @available(*, deprecated, message: "Strideable conformance where 'Stride == Self' requires user-defined implementation of the '<' operator") |
| public static func < (x: Self, y: Self) -> Bool { |
| fatalError(""" |
| Strideable conformance where 'Stride == Self' requires user-defined \ |
| implementation of the '<' operator |
| """) |
| } |
| |
| @available(*, deprecated, message: "Strideable conformance where 'Stride == Self' requires user-defined implementation of the '==' operator") |
| public static func == (x: Self, y: Self) -> Bool { |
| fatalError(""" |
| Strideable conformance where 'Stride == Self' requires user-defined \ |
| implementation of the '==' operator |
| """) |
| } |
| } |
| |
| 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} { |
| @_transparent |
| ${Availability} |
| public static func + (lhs: Self, rhs: Self.Stride) -> Self { |
| return lhs.advanced(by: rhs) |
| } |
| |
| @_transparent |
| ${Availability} |
| public static func + (lhs: Self.Stride, rhs: Self) -> Self { |
| return rhs.advanced(by: lhs) |
| } |
| |
| @_transparent |
| ${Availability} |
| public static func - (lhs: Self, rhs: Self.Stride) -> Self { |
| return lhs.advanced(by: -rhs) |
| } |
| |
| @_transparent |
| ${Availability} |
| public static func - (lhs: Self, rhs: Self) -> Self.Stride { |
| return rhs.distance(to: lhs) |
| } |
| |
| @_transparent |
| ${Availability} |
| public static func += (lhs: inout Self, rhs: Self.Stride) { |
| lhs = lhs.advanced(by: rhs) |
| } |
| |
| @_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 { |
| return (i + 1, start.advanced(by: Stride(i + 1) * distance)) |
| } |
| // If current.index == nil, either we're just starting out (in which case |
| // the next index is 1), or we should proceed without an index just as |
| // though this floating point specialization doesn't exist. |
| return (current.value == start ? 1 : nil, |
| current.value.advanced(by: distance)) |
| } |
| } |
| |
| /// An iterator for `StrideTo<Element>`. |
| @_fixed_layout |
| public struct StrideToIterator<Element : Strideable> : IteratorProtocol { |
| @_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 = (nil, _start) |
| } |
| |
| /// 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. |
| @_fixed_layout |
| public struct StrideTo<Element : Strideable> : Sequence, CustomReflectable { |
| // FIXME: should really be a Collection, as it is multipass |
| |
| /// 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) |
| } |
| |
| @_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 |
| } |
| |
| @_versioned |
| internal let _start: Element |
| |
| @_versioned |
| internal let _end: Element |
| |
| @_versioned |
| internal let _stride: Element.Stride |
| |
| public var customMirror: Mirror { |
| return Mirror(self, children: ["from": _start, "to": _end, "by": _stride]) |
| } |
| } |
| |
| /// 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> : IteratorProtocol { |
| @_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 = (nil, _start) |
| } |
| |
| /// 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. |
| @_fixed_layout |
| public struct StrideThrough< |
| Element : Strideable |
| > : Sequence, CustomReflectable { |
| // FIXME: should really be a CollectionType, as it is multipass |
| |
| /// 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) |
| } |
| |
| @_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 |
| } |
| |
| @_versioned |
| internal let _start: Element |
| @_versioned |
| internal let _end: Element |
| @_versioned |
| internal let _stride: Element.Stride |
| |
| public var customMirror: Mirror { |
| return Mirror(self, |
| children: ["from": _start, "through": _end, "by": _stride]) |
| } |
| } |
| |
| /// 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) |
| } |