| //===--- Stride.swift.gyb - Components for stride(...) iteration ----------===// |
| // |
| // This source file is part of the Swift.org open source project |
| // |
| // Copyright (c) 2014 - 2016 Apple Inc. and the Swift project authors |
| // Licensed under Apache License v2.0 with Runtime Library Exception |
| // |
| // See http://swift.org/LICENSE.txt for license information |
| // See http://swift.org/CONTRIBUTORS.txt for the list of Swift project authors |
| // |
| //===----------------------------------------------------------------------===// |
| |
| // FIXME(ABI)(compiler limitation): 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. |
| public protocol ${Self} : ${Conformance} { |
| /// A type that can represent the distance between two values of `Self`. |
| associatedtype Stride : SignedNumber |
| |
| /// 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 |
| |
| /// Compare two `Strideable`s. |
| public func < <T : Strideable>(x: T, y: T) -> Bool { |
| return x.distance(to: y) > 0 |
| } |
| |
| public func == <T : Strideable>(x: T, y: T) -> Bool { |
| return x.distance(to: y) == 0 |
| } |
| |
| public func + <T : Strideable>(lhs: T, rhs: T.Stride) -> T { |
| return lhs.advanced(by: rhs) |
| } |
| |
| public func + <T : Strideable>(lhs: T.Stride, rhs: T) -> T { |
| return rhs.advanced(by: lhs) |
| } |
| |
| public func - <T : Strideable>(lhs: T, rhs: T.Stride) -> T { |
| return lhs.advanced(by: -rhs) |
| } |
| |
| public func - <T : Strideable>(lhs: T, rhs: T) -> T.Stride { |
| return rhs.distance(to: lhs) |
| } |
| |
| public func += <T : Strideable>(lhs: inout T, rhs: T.Stride) { |
| lhs = lhs.advanced(by: rhs) |
| } |
| |
| public func -= <T : Strideable>(lhs: inout T, rhs: T.Stride) { |
| lhs = lhs.advanced(by: -rhs) |
| } |
| |
| //===--- Deliberately-ambiguous operators for UnsignedIntegerTypes --------===// |
| // The UnsignedIntegerTypes all have a signed Stride type. Without these // |
| // overloads, expressions such as UInt(2) + Int(3) would compile. // |
| //===----------------------------------------------------------------------===// |
| |
| public func + <T : UnsignedInteger>( |
| lhs: T, rhs: T._DisallowMixedSignArithmetic |
| ) -> T { |
| _sanityCheckFailure("Should not be callable.") |
| } |
| |
| public func + <T : UnsignedInteger>( |
| lhs: T._DisallowMixedSignArithmetic, rhs: T |
| ) -> T { |
| _sanityCheckFailure("Should not be callable.") |
| } |
| |
| public func - <T : _DisallowMixedSignArithmetic>( |
| lhs: T, rhs: T._DisallowMixedSignArithmetic |
| ) -> T { |
| _sanityCheckFailure("Should not be callable.") |
| } |
| |
| public func - <T : _DisallowMixedSignArithmetic>( |
| lhs: T, rhs: T |
| ) -> T._DisallowMixedSignArithmetic { |
| _sanityCheckFailure("Should not be callable.") |
| } |
| |
| public func += <T : UnsignedInteger>( |
| lhs: inout T, rhs: T._DisallowMixedSignArithmetic |
| ) { |
| _sanityCheckFailure("Should not be callable.") |
| } |
| |
| public func -= <T : UnsignedInteger>( |
| lhs: inout T, rhs: T._DisallowMixedSignArithmetic |
| ) { |
| _sanityCheckFailure("Should not be callable.") |
| } |
| |
| //===----------------------------------------------------------------------===// |
| |
| extension Strideable { |
| 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 + distance) |
| } |
| } |
| |
| extension Strideable where Stride : FloatingPoint { |
| 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 + 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 + distance) |
| } |
| } |
| |
| /// An iterator for `StrideTo<Element>`. |
| public struct StrideToIterator<Element : Strideable> : IteratorProtocol { |
| internal let _start: Element |
| internal let _end: Element |
| internal let _stride: Element.Stride |
| internal var _current: (index: Int?, value: Element) |
| |
| 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`. |
| 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. |
| 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). |
| public func makeIterator() -> StrideToIterator<Element> { |
| return StrideToIterator(_start: _start, end: _end, stride: _stride) |
| } |
| |
| 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 |
| } |
| |
| internal let _start: Element |
| internal let _end: Element |
| 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`. |
| public func stride<T : Strideable>( |
| 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>`. |
| public struct StrideThroughIterator<Element : Strideable> : IteratorProtocol { |
| internal let _start: Element |
| internal let _end: Element |
| internal let _stride: Element.Stride |
| internal var _current: (index: Int?, value: Element) |
| internal var _didReturnEnd: Bool = false |
| |
| 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`. |
| 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. |
| 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). |
| public func makeIterator() -> StrideThroughIterator<Element> { |
| return StrideThroughIterator(_start: _start, end: _end, stride: _stride) |
| } |
| |
| 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 |
| } |
| |
| internal let _start: Element |
| internal let _end: Element |
| 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. |
| public func stride<T : Strideable>( |
| from start: T, through end: T, by stride: T.Stride |
| ) -> StrideThrough<T> { |
| return StrideThrough(_start: start, end: end, stride: stride) |
| } |
| |
| @available(*, unavailable, renamed: "StrideToIterator") |
| public struct StrideToGenerator<Element : Strideable> {} |
| |
| @available(*, unavailable, renamed: "StrideThroughIterator") |
| public struct StrideThroughGenerator<Element : Strideable> {} |
| |
| extension Strideable { |
| @available(*, unavailable, message: "Use stride(from:to:by:) free function instead") |
| public func stride(to end: Self, by stride: Stride) -> StrideTo<Self> { |
| Builtin.unreachable() |
| } |
| |
| @warn_unqualified_access |
| @available(*, unavailable, message: "Use stride(from:through:by:) free function instead") |
| public func stride( |
| through end: Self, by stride: Stride |
| ) -> StrideThrough<Self> { |
| Builtin.unreachable() |
| } |
| } |