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4ddac3fbbd
* Eradicate IndexDistance associated type, replacing with Int everywhere * Consistently use Int for ExistentialCollection’s IndexDistance type. * Fix test for IndexDistance removal * Remove a handful of no-longer-needed explicit types * Add compatibility shims for non-Int index distances * Test compatibility shim * Move IndexDistance typealias into the Collection protocol
522 lines
15 KiB
Plaintext
522 lines
15 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 - 2017 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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/// Conforming types are notionally continuous, one-dimensional
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/// values that can be offset and measured.
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///
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/// - Important: The `Strideable` protocol provides default implementations for
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/// the equal-to (`==`) and less-than (`<`) operators that depend on the
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/// `Stride` type's implementations. If a type conforming to `Strideable`
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/// is its own `Stride` type, it must provide concrete implementations of
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/// the two operators to avoid infinite recursion.
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public protocol Strideable : Comparable {
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/// A type that represents the distance between two values of `Self`.
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associatedtype Stride : SignedNumeric, Comparable
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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 = Never
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}
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extension Strideable {
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@_inlineable
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public static func < (x: Self, y: Self) -> Bool {
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return x.distance(to: y) > 0
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}
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@_inlineable
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public static func == (x: Self, y: Self) -> Bool {
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return x.distance(to: y) == 0
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}
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}
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//===----------------------------------------------------------------------===//
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%{
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# Strideable used to provide + and - unconditionally. With the updated
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# collection indexing model of Swift 3 this became unnecessary for integer
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# types, and was deprecated, as it was a way to write mixed-type arithmetic
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# expressions, that are otherwise are not allowed.
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}%
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% for Base, VersionInfo in [
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% ('Strideable where Self : _Pointer', None),
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% ('Strideable', 'deprecated: 3, obsoleted: 4'),
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% ]:
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% Availability = '@available(swift, %s, message: "Please use explicit type conversions or Strideable methods for mixed-type arithmetics.")' % (VersionInfo) if VersionInfo else ''
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extension ${Base} {
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@_inlineable // FIXME(sil-serialize-all)
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@_transparent
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${Availability}
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public static func + (lhs: Self, rhs: Self.Stride) -> Self {
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return lhs.advanced(by: rhs)
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}
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@_inlineable // FIXME(sil-serialize-all)
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@_transparent
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${Availability}
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public static func + (lhs: Self.Stride, rhs: Self) -> Self {
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return rhs.advanced(by: lhs)
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}
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@_inlineable // FIXME(sil-serialize-all)
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@_transparent
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${Availability}
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public static func - (lhs: Self, rhs: Self.Stride) -> Self {
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return lhs.advanced(by: -rhs)
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}
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@_inlineable // FIXME(sil-serialize-all)
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@_transparent
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${Availability}
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public static func - (lhs: Self, rhs: Self) -> Self.Stride {
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return rhs.distance(to: lhs)
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}
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@_inlineable // FIXME(sil-serialize-all)
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@_transparent
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${Availability}
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public static func += (lhs: inout Self, rhs: Self.Stride) {
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lhs = lhs.advanced(by: rhs)
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}
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@_inlineable // FIXME(sil-serialize-all)
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@_transparent
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${Availability}
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public static func -= (lhs: inout Self, rhs: Self.Stride) {
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lhs = lhs.advanced(by: -rhs)
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}
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}
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% end
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//===----------------------------------------------------------------------===//
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extension Strideable {
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@_inlineable
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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.advanced(by: distance))
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}
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}
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extension Strideable where Stride : FloatingPoint {
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@_inlineable
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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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// When Stride is a floating-point type, we should avoid accumulating
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// rounding error from repeated addition.
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return (i + 1, start.advanced(by: Stride(i + 1) * distance))
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}
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return (nil, current.value.advanced(by: distance))
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}
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}
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extension Strideable where Self : FloatingPoint, Self == Stride {
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@_inlineable
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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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// When both Self and Stride are the same floating-point type, we should
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// take advantage of fused multiply-add (where supported) to eliminate
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// intermediate rounding error.
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return (i + 1, start.addingProduct(Stride(i + 1), distance))
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}
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return (nil, current.value.advanced(by: distance))
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}
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}
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/// An iterator for `StrideTo<Element>`.
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@_fixed_layout
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public struct StrideToIterator<Element : Strideable> {
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@_versioned
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internal let _start: Element
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@_versioned
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internal let _end: Element
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@_versioned
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internal let _stride: Element.Stride
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@_versioned
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internal var _current: (index: Int?, value: Element)
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@_inlineable
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@_versioned
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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 = (0, _start)
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}
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}
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extension StrideToIterator: IteratorProtocol {
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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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@_inlineable
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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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// FIXME: should really be a Collection, as it is multipass
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@_fixed_layout
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public struct StrideTo<Element : Strideable> {
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@_versioned
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internal let _start: Element
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@_versioned
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internal let _end: Element
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@_versioned
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internal let _stride: Element.Stride
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@_inlineable
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@_versioned
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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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}
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extension StrideTo: Sequence {
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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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@_inlineable
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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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// FIXME(conditional-conformances): this is O(N) instead of O(1), leaving it
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// here until a proper Collection conformance is possible
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@_inlineable
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public var underestimatedCount: Int {
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var it = self.makeIterator()
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var count = 0
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while it.next() != nil {
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count += 1
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}
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return count
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}
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@_inlineable
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public func _preprocessingPass<R>(
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_ preprocess: () throws -> R
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) rethrows -> R? {
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return try preprocess()
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}
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@_inlineable
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public func _customContainsEquatableElement(
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_ element: Element
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) -> Bool? {
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if element < _start || _end <= element {
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return false
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}
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return nil
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}
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}
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extension StrideTo: CustomReflectable {
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@_inlineable // FIXME(sil-serialize-all)
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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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// FIXME(conditional-conformances): This does not yet compile (SR-6474).
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#if false
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extension StrideTo : RandomAccessCollection
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where Element.Stride : BinaryInteger {
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public typealias Index = Int
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public typealias SubSequence = Slice<StrideTo<Element>>
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public typealias Indices = CountableRange<Int>
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@_inlineable
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public var startIndex: Index { return 0 }
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@_inlineable
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public var endIndex: Index { return count }
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@_inlineable
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public var count: Int {
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let distance = _start.distance(to: _end)
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guard distance != 0 && (distance < 0) == (_stride < 0) else { return 0 }
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return Int((distance - 1) / _stride) + 1
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}
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public subscript(position: Index) -> Element {
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_failEarlyRangeCheck(position, bounds: startIndex..<endIndex)
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return _start.advanced(by: Element.Stride(position) * _stride)
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}
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public subscript(bounds: Range<Index>) -> Slice<StrideTo<Element>> {
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_failEarlyRangeCheck(bounds, bounds: startIndex ..< endIndex)
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return Slice(base: self, bounds: bounds)
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}
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@_inlineable
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public func index(before i: Index) -> Index {
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_failEarlyRangeCheck(i, bounds: startIndex + 1...endIndex)
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return i - 1
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}
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@_inlineable
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public func index(after i: Index) -> Index {
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_failEarlyRangeCheck(i, bounds: startIndex - 1..<endIndex)
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return i + 1
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}
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}
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#endif
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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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@_inlineable
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public func stride<T>(
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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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@_fixed_layout
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public struct StrideThroughIterator<Element : Strideable> {
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@_versioned
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internal let _start: Element
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@_versioned
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internal let _end: Element
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@_versioned
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internal let _stride: Element.Stride
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@_versioned
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internal var _current: (index: Int?, value: Element)
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@_versioned
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internal var _didReturnEnd: Bool = false
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@_inlineable
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@_versioned
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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 = (0, _start)
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}
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}
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extension StrideThroughIterator: IteratorProtocol {
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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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@_inlineable
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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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// FIXME: should really be a CollectionType, as it is multipass
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@_fixed_layout
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public struct StrideThrough<Element: Strideable> {
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@_versioned
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internal let _start: Element
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@_versioned
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internal let _end: Element
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@_versioned
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internal let _stride: Element.Stride
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@_inlineable
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@_versioned
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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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}
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extension StrideThrough: Sequence {
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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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@_inlineable
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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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// FIXME(conditional-conformances): this is O(N) instead of O(1), leaving it
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// here until a proper Collection conformance is possible
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@_inlineable
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public var underestimatedCount: Int {
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var it = self.makeIterator()
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var count = 0
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while it.next() != nil {
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count += 1
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}
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return count
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}
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@_inlineable
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public func _preprocessingPass<R>(
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_ preprocess: () throws -> R
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) rethrows -> R? {
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return try preprocess()
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}
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@_inlineable
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public func _customContainsEquatableElement(
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_ element: Element
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) -> Bool? {
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if element < _start || _end < element {
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return false
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}
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return nil
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}
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}
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extension StrideThrough: CustomReflectable {
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@_inlineable // FIXME(sil-serialize-all)
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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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// FIXME(conditional-conformances): This does not yet compile (SR-6474).
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#if false
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extension StrideThrough : RandomAccessCollection
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where Element.Stride : BinaryInteger {
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public typealias Index = ClosedRangeIndex<Int>
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public typealias SubSequence = Slice<StrideThrough<Element>>
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@_inlineable
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public var startIndex: Index {
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let distance = _start.distance(to: _end)
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return distance == 0 || (distance < 0) == (_stride < 0)
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? ClosedRangeIndex(0)
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: ClosedRangeIndex()
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}
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@_inlineable
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public var endIndex: Index { return ClosedRangeIndex() }
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@_inlineable
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public var count: Int {
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let distance = _start.distance(to: _end)
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guard distance != 0 else { return 1 }
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guard (distance < 0) == (_stride < 0) else { return 0 }
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return Int(distance / _stride) + 1
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}
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public subscript(position: Index) -> Element {
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let offset = Element.Stride(position._dereferenced) * _stride
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return _start.advanced(by: offset)
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}
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public subscript(bounds: Range<Index>) -> Slice<StrideThrough<Element>> {
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return Slice(base: self, bounds: bounds)
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}
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@_inlineable
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public func index(before i: Index) -> Index {
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switch i._value {
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case .inRange(let n):
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_precondition(n > 0, "Incrementing past start index")
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return ClosedRangeIndex(n - 1)
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case .pastEnd:
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_precondition(_end >= _start, "Incrementing past start index")
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return ClosedRangeIndex(count - 1)
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}
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}
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@_inlineable
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public func index(after i: Index) -> Index {
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switch i._value {
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case .inRange(let n):
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return n == (count - 1)
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? ClosedRangeIndex()
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: ClosedRangeIndex(n + 1)
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case .pastEnd:
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_preconditionFailure("Incrementing past end index")
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}
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}
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}
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#endif
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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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@_inlineable
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public func stride<T>(
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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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