74 lines
2.0 KiB
Swift
74 lines
2.0 KiB
Swift
//
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// Comparable.swift
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// BigInt
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//
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// Created by Károly Lőrentey on 2016-01-03.
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// Copyright © 2016-2017 Károly Lőrentey.
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//
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#if canImport(Foundation)
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import Foundation
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#endif
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extension BigUInt: Comparable {
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#if !canImport(Foundation)
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public enum ComparisonResult: Sendable, Comparable, Hashable {
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case orderedDescending
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case orderedSame
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case orderedAscending
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}
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#endif
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//MARK: Comparison
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/// Compare `a` to `b` and return an `NSComparisonResult` indicating their order.
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///
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/// - Complexity: O(count)
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public static func compare(_ a: BigUInt, _ b: BigUInt) -> ComparisonResult {
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if a.count != b.count { return a.count > b.count ? .orderedDescending : .orderedAscending }
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for i in (0 ..< a.count).reversed() {
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let ad = a[i]
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let bd = b[i]
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if ad != bd { return ad > bd ? .orderedDescending : .orderedAscending }
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}
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return .orderedSame
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}
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/// Return true iff `a` is equal to `b`.
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///
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/// - Complexity: O(count)
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public static func ==(a: BigUInt, b: BigUInt) -> Bool {
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return BigUInt.compare(a, b) == .orderedSame
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}
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/// Return true iff `a` is less than `b`.
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///
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/// - Complexity: O(count)
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public static func <(a: BigUInt, b: BigUInt) -> Bool {
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return BigUInt.compare(a, b) == .orderedAscending
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}
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}
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extension BigInt: Comparable {
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/// Return true iff `a` is equal to `b`.
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public static func ==(a: BigInt, b: BigInt) -> Bool {
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return a.sign == b.sign && a.magnitude == b.magnitude
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}
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/// Return true iff `a` is less than `b`.
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public static func <(a: BigInt, b: BigInt) -> Bool {
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switch (a.sign, b.sign) {
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case (.plus, .plus):
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return a.magnitude < b.magnitude
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case (.plus, .minus):
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return false
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case (.minus, .plus):
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return true
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case (.minus, .minus):
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return a.magnitude > b.magnitude
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}
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}
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}
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