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319 lines
10 KiB
Plaintext
319 lines
10 KiB
Plaintext
//===--- Stride.swift.gyb - Components for stride(...) iteration ----------===//
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//
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// This source file is part of the Swift.org open source project
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//
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// Copyright (c) 2014 - 2016 Apple Inc. and the Swift project authors
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// Licensed under Apache License v2.0 with Runtime Library Exception
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//
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// See https://swift.org/LICENSE.txt for license information
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// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
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//
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//===----------------------------------------------------------------------===//
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// FIXME(ABI)#69 (Overload Resolution): Remove `_Strideable`.
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// WORKAROUND rdar://25214598 - should be:
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// protocol Strideable : Comparable {...}
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% for Self in ['_Strideable', 'Strideable']:
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%{
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Conformance = (
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'Equatable' if Self == '_Strideable' else '_Strideable, Comparable'
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)
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}%
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/// Conforming types are notionally continuous, one-dimensional
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/// values that can be offset and measured.
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public protocol ${Self} : ${Conformance} {
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/// A type that can represent the distance between two values of `Self`.
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associatedtype Stride : SignedNumber
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/// Returns a stride `x` such that `self.advanced(by: x)` approximates
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/// `other`.
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///
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/// If `Stride` conforms to `Integer`, then `self.advanced(by: x) == other`.
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///
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/// - Complexity: O(1).
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func distance(to other: Self) -> Stride
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/// Returns a `Self` `x` such that `self.distance(to: x)` approximates `n`.
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///
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/// If `Stride` conforms to `Integer`, then `self.distance(to: x) == n`.
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///
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/// - Complexity: O(1).
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func advanced(by n: Stride) -> Self
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/// `_step` is an implementation detail of Strideable; do not use it directly.
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static func _step(
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after current: (index: Int?, value: Self),
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from start: Self, by distance: Self.Stride
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) -> (index: Int?, value: Self)
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associatedtype _DisabledRangeIndex = _DisabledRangeIndex_
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}
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% end
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/// Compare two `Strideable`s.
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public func < <T : Strideable>(x: T, y: T) -> Bool {
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return x.distance(to: y) > 0
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}
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public func == <T : Strideable>(x: T, y: T) -> Bool {
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return x.distance(to: y) == 0
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}
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public func + <T : Strideable>(lhs: T, rhs: T.Stride) -> T {
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return lhs.advanced(by: rhs)
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}
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public func + <T : Strideable>(lhs: T.Stride, rhs: T) -> T {
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return rhs.advanced(by: lhs)
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}
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public func - <T : Strideable>(lhs: T, rhs: T.Stride) -> T {
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return lhs.advanced(by: -rhs)
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}
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public func - <T : Strideable>(lhs: T, rhs: T) -> T.Stride {
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return rhs.distance(to: lhs)
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}
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public func += <T : Strideable>(lhs: inout T, rhs: T.Stride) {
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lhs = lhs.advanced(by: rhs)
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}
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public func -= <T : Strideable>(lhs: inout T, rhs: T.Stride) {
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lhs = lhs.advanced(by: -rhs)
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}
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//===--- Deliberately-ambiguous operators for UnsignedIntegerTypes --------===//
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// The UnsignedIntegerTypes all have a signed Stride type. Without these //
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// overloads, expressions such as UInt(2) + Int(3) would compile. //
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//===----------------------------------------------------------------------===//
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public func + <T : UnsignedInteger>(
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lhs: T, rhs: T._DisallowMixedSignArithmetic
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) -> T {
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_sanityCheckFailure("Should not be callable.")
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}
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public func + <T : UnsignedInteger>(
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lhs: T._DisallowMixedSignArithmetic, rhs: T
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) -> T {
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_sanityCheckFailure("Should not be callable.")
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}
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public func - <T : _DisallowMixedSignArithmetic>(
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lhs: T, rhs: T._DisallowMixedSignArithmetic
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) -> T {
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_sanityCheckFailure("Should not be callable.")
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}
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public func - <T : _DisallowMixedSignArithmetic>(
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lhs: T, rhs: T
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) -> T._DisallowMixedSignArithmetic {
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_sanityCheckFailure("Should not be callable.")
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}
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public func += <T : UnsignedInteger>(
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lhs: inout T, rhs: T._DisallowMixedSignArithmetic
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) {
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_sanityCheckFailure("Should not be callable.")
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}
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public func -= <T : UnsignedInteger>(
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lhs: inout T, rhs: T._DisallowMixedSignArithmetic
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) {
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_sanityCheckFailure("Should not be callable.")
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}
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//===----------------------------------------------------------------------===//
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extension Strideable {
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public static func _step(
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after current: (index: Int?, value: Self),
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from start: Self, by distance: Self.Stride
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) -> (index: Int?, value: Self) {
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return (nil, current.value + distance)
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}
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}
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extension Strideable where Stride : FloatingPoint {
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public static func _step(
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after current: (index: Int?, value: Self),
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from start: Self, by distance: Self.Stride
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) -> (index: Int?, value: Self) {
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if let i = current.index {
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return (i + 1, start + Stride(i + 1) * distance)
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}
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// If current.index == nil, either we're just starting out (in which case
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// the next index is 1), or we should proceed without an index just as
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// though this floating point specialization doesn't exist.
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return (current.value == start ? 1 : nil, current.value + distance)
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}
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}
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/// An iterator for `StrideTo<Element>`.
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public struct StrideToIterator<Element : Strideable> : IteratorProtocol {
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internal let _start: Element
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internal let _end: Element
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internal let _stride: Element.Stride
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internal var _current: (index: Int?, value: Element)
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internal init(_start: Element, end: Element, stride: Element.Stride) {
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self._start = _start
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_end = end
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_stride = stride
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_current = (nil, _start)
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}
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/// Advances to the next element and returns it, or `nil` if no next element
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/// exists.
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///
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/// Once `nil` has been returned, all subsequent calls return `nil`.
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public mutating func next() -> Element? {
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let result = _current.value
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if _stride > 0 ? result >= _end : result <= _end {
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return nil
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}
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_current = Element._step(after: _current, from: _start, by: _stride)
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return result
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}
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}
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/// A `Sequence` of values formed by striding over a half-open interval.
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public struct StrideTo<Element : Strideable> : Sequence, CustomReflectable {
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// FIXME: should really be a Collection, as it is multipass
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/// Returns an iterator over the elements of this sequence.
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///
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/// - Complexity: O(1).
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public func makeIterator() -> StrideToIterator<Element> {
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return StrideToIterator(_start: _start, end: _end, stride: _stride)
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}
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internal init(_start: Element, end: Element, stride: Element.Stride) {
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_precondition(stride != 0, "stride size must not be zero")
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// At start, striding away from end is allowed; it just makes for an
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// already-empty Sequence.
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self._start = _start
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self._end = end
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self._stride = stride
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}
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internal let _start: Element
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internal let _end: Element
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internal let _stride: Element.Stride
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public var customMirror: Mirror {
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return Mirror(self, children: ["from": _start, "to": _end, "by": _stride])
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}
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}
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/// Returns the sequence of values (`self`, `self + stride`, `self +
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/// 2 * stride`, ... *last*) where *last* is the last value in the
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/// progression that is less than `end`.
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public func stride<T : Strideable>(
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from start: T, to end: T, by stride: T.Stride
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) -> StrideTo<T> {
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return StrideTo(_start: start, end: end, stride: stride)
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}
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/// An iterator for `StrideThrough<Element>`.
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public struct StrideThroughIterator<Element : Strideable> : IteratorProtocol {
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internal let _start: Element
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internal let _end: Element
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internal let _stride: Element.Stride
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internal var _current: (index: Int?, value: Element)
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internal var _didReturnEnd: Bool = false
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internal init(_start: Element, end: Element, stride: Element.Stride) {
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self._start = _start
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_end = end
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_stride = stride
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_current = (nil, _start)
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}
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/// Advances to the next element and returns it, or `nil` if no next element
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/// exists.
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///
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/// Once `nil` has been returned, all subsequent calls return `nil`.
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public mutating func next() -> Element? {
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let result = _current.value
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if _stride > 0 ? result >= _end : result <= _end {
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// This check is needed because if we just changed the above operators
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// to > and <, respectively, we might advance current past the end
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// and throw it out of bounds (e.g. above Int.max) unnecessarily.
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if result == _end && !_didReturnEnd {
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_didReturnEnd = true
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return result
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}
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return nil
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}
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_current = Element._step(after: _current, from: _start, by: _stride)
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return result
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}
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}
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/// A `Sequence` of values formed by striding over a closed interval.
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public struct StrideThrough<
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Element : Strideable
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> : Sequence, CustomReflectable {
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// FIXME: should really be a CollectionType, as it is multipass
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/// Returns an iterator over the elements of this sequence.
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///
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/// - Complexity: O(1).
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public func makeIterator() -> StrideThroughIterator<Element> {
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return StrideThroughIterator(_start: _start, end: _end, stride: _stride)
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}
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internal init(_start: Element, end: Element, stride: Element.Stride) {
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_precondition(stride != 0, "stride size must not be zero")
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self._start = _start
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self._end = end
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self._stride = stride
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}
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internal let _start: Element
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internal let _end: Element
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internal let _stride: Element.Stride
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public var customMirror: Mirror {
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return Mirror(self,
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children: ["from": _start, "through": _end, "by": _stride])
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}
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}
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/// Returns the sequence of values (`self`, `self + stride`, `self +
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/// 2 * stride`, ... *last*) where *last* is the last value in the
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/// progression less than or equal to `end`.
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///
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/// - Note: There is no guarantee that `end` is an element of the sequence.
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public func stride<T : Strideable>(
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from start: T, through end: T, by stride: T.Stride
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) -> StrideThrough<T> {
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return StrideThrough(_start: start, end: end, stride: stride)
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}
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@available(*, unavailable, renamed: "StrideToIterator")
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public struct StrideToGenerator<Element : Strideable> {}
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@available(*, unavailable, renamed: "StrideThroughIterator")
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public struct StrideThroughGenerator<Element : Strideable> {}
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extension Strideable {
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@available(*, unavailable, message: "Use stride(from:to:by:) free function instead")
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public func stride(to end: Self, by stride: Stride) -> StrideTo<Self> {
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Builtin.unreachable()
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}
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@warn_unqualified_access
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@available(*, unavailable, message: "Use stride(from:through:by:) free function instead")
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public func stride(
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through end: Self, by stride: Stride
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) -> StrideThrough<Self> {
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Builtin.unreachable()
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}
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}
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