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//===--- OptionalDifferentiation.swift ------------------------*- swift -*-===//
//
// This source file is part of the Swift.org open source project
//
// Copyright (c) 2020 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
//
//===----------------------------------------------------------------------===//
import Swift
extension Optional: Differentiable where Wrapped: Differentiable {
@frozen
public struct TangentVector: Differentiable, AdditiveArithmetic {
public typealias TangentVector = Self
public var value: Wrapped.TangentVector?
public init(_ value: Wrapped.TangentVector?) {
self.value = value
}
public static var zero: Self {
return Self(.zero)
}
public static func + (lhs: Self, rhs: Self) -> Self {
switch (lhs.value, rhs.value) {
case (nil, nil): return Self(nil)
case let (x?, nil): return Self(x)
case let (nil, y?): return Self(y)
case let (x?, y?): return Self(x + y)
}
}
public static func - (lhs: Self, rhs: Self) -> Self {
switch (lhs.value, rhs.value) {
case (nil, nil): return Self(nil)
case let (x?, nil): return Self(x)
case let (nil, y?): return Self(.zero - y)
case let (x?, y?): return Self(x - y)
}
}
public mutating func move(by offset: TangentVector) {
if let value = offset.value {
self.value?.move(by: value)
}
}
}
public mutating func move(by offset: TangentVector) {
if let value = offset.value {
self?.move(by: value)
}
}
}
extension Optional.TangentVector: CustomReflectable {
public var customMirror: Mirror {
return value.customMirror
}
}
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