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NSIndexSet+Snippets.swift
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NSIndexSet+Snippets.swift
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// Snippets NSIndexSet+Snippets.swift
//
// Copyright © 2016, Roy Ratcliffe, Pioneering Software, United Kingdom
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the “Software”), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED “AS IS,” WITHOUT WARRANTY OF ANY KIND, EITHER
// EXPRESSED OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO
// EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES
// OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
// ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
// DEALINGS IN THE SOFTWARE.
//
//------------------------------------------------------------------------------
import Foundation
extension NSIndexSet {
/// - returns: the first available range unless there are no indexes because
/// the index set is empty.
public var firstRange: NSRange? {
var firstRange: NSRange?
enumerateRanges(options: []) { (range, stop) -> Void in
firstRange = range
stop.pointee = true
}
return firstRange
}
/// - returns: the last range in the index set, or `nil` if an empty set.
public var lastRange: NSRange? {
var lastRange: NSRange?
enumerateRanges(options: .reverse) { (range, stop) -> Void in
lastRange = range
stop.pointee = true
}
return lastRange
}
/// - returns: an array of ranges.
///
/// Index sets internally implement the set as a collection of NSRange
/// objects. Enumerates all ranges, constructing an immutable array of
/// ranges. Returns the result.
public var ranges: [NSRange] {
var ranges = [NSRange]()
enumerateRanges(options: []) { (range, _) -> Void in
ranges.append(range)
}
return ranges
}
/// Adds this index set to another.
public func union(_ other: IndexSet) -> IndexSet {
let selfPlusOther = NSMutableIndexSet()
selfPlusOther.add(self as IndexSet)
selfPlusOther.add(other)
return selfPlusOther as IndexSet
}
/// - returns: the set of all indexes in this set that also belong to another.
public func intersect(_ other: IndexSet) -> IndexSet {
let intersect = NSMutableIndexSet()
intersect.add(self as IndexSet)
intersect.add(other)
intersect.remove(symmetricDifference(other))
return intersect as IndexSet
}
/// Computes the difference between two index sets excluding any indexes in
/// common. This amounts to computing the set: self minus the other, plus the
/// other minus self.
/// - returns: the difference between this index set and another index set
/// where the symmetric result *excludes* indexes that appear in both this
/// and the other set.
public func symmetricDifference(_ other: IndexSet) -> IndexSet {
let otherMinusSelf = NSMutableIndexSet()
otherMinusSelf.add(other)
otherMinusSelf.remove(self as IndexSet)
let selfMinusOtherPlusOtherMinusSelf = NSMutableIndexSet()
selfMinusOtherPlusOtherMinusSelf.add(self as IndexSet)
selfMinusOtherPlusOtherMinusSelf.remove(other)
selfMinusOtherPlusOtherMinusSelf.add(otherMinusSelf as IndexSet)
return selfMinusOtherPlusOtherMinusSelf as IndexSet
}
/// Conveniently constructs a new index set using an array of indexes.
public convenience init(indexes: [Int]) {
let indexSet = NSMutableIndexSet()
for index in indexes {
indexSet.add(index)
}
self.init(indexSet: indexSet as IndexSet)
}
}