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//===--- RangeSelection.swift ---------------------------------------------===//
//
// This source file is part of the Swift.org open source project
//
// Copyright (c) 2014 - 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 StdlibUnittest
public enum RangeSelection {
case emptyRange
case leftEdge
case rightEdge
case middle
case leftHalf
case rightHalf
case full
case offsets(Int, Int)
public var isEmpty: Bool {
switch self {
case .emptyRange: return true
default: return false
}
}
public func range<C : Collection>(in c: C) -> Range<C.Index> {
switch self {
case .emptyRange: return c.endIndex..<c.endIndex
case .leftEdge: return c.startIndex..<c.startIndex
case .rightEdge: return c.endIndex..<c.endIndex
case .middle:
let start = c.index(c.startIndex, offsetBy: c.count / 4)
let end = c.index(c.startIndex, offsetBy: 3 * c.count / 4 + 1)
return start..<end
case .leftHalf:
let start = c.startIndex
let end = c.index(start, offsetBy: c.count / 2)
return start..<end
case .rightHalf:
let start = c.index(c.startIndex, offsetBy: c.count / 2)
let end = c.endIndex
return start..<end
case .full:
return c.startIndex..<c.endIndex
case let .offsets(lowerBound, upperBound):
let start = c.index(c.startIndex, offsetBy: lowerBound)
let end = c.index(c.startIndex, offsetBy: upperBound)
return start..<end
}
}
public func closedRange<C : Collection>(in c: C) -> ClosedRange<C.Index> {
switch self {
case .emptyRange: fatalError("Closed range cannot be empty")
case .leftEdge: return c.startIndex...c.startIndex
case .rightEdge:
let beforeEnd = c.index(c.startIndex, offsetBy: c.count - 1)
return beforeEnd...beforeEnd
case .middle:
let start = c.index(c.startIndex, offsetBy: c.count / 4)
let end = c.index(c.startIndex, offsetBy: 3 * c.count / 4)
return start...end
case .leftHalf:
let start = c.startIndex
let end = c.index(start, offsetBy: c.count / 2 - 1)
return start...end
case .rightHalf:
let start = c.index(c.startIndex, offsetBy: c.count / 2)
let beforeEnd = c.index(c.startIndex, offsetBy: c.count - 1)
return start...beforeEnd
case .full:
let beforeEnd = c.index(c.startIndex, offsetBy: c.count - 1)
return c.startIndex...beforeEnd
case let .offsets(lowerBound, upperBound):
let start = c.index(c.startIndex, offsetBy: lowerBound)
let end = c.index(c.startIndex, offsetBy: upperBound)
return start...end
}
}
}
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