Swift - Liberated functions: First Class Functions(isOrderedBefore(comparison function), descending order, Array(sort method, sorted method, immutable, in-place, new array))

The Swift Programming Language
Apple Inc.

開発環境

• OS X Mavericks - Apple(OS)
• Xcode 6.0 Beta
• Swift (プログラミング言語)

Head First JavaScript Programming (Eric T. Freeman (著)、 Elisabeth Robson (著)、 O'Reilly Media )のChapter 10(Liberated functions: First Class Functions)、EXERCISE(p.460)をSwiftで考えてみる。

EXERCISE(p.460)

コード(Xcode)

main.swift

//
//  main.swift
//  sample460
//
//  Created by kamimura on 9/14/14.
//  Copyright (c) 2014 kamimura. All rights reserved.
//

import Foundation

func compareNumbersDesc(num1:Int, num2:Int) -> Bool {
    if num2 > num1 {
        return false
    }
    return true
}

for x in 1...5 {
    for y in 1...5 {
        println("\(x) \(y) \(compareNumbersDesc(x, y))")
    }
}

var nums:[Int] = [5, 1, 4, 2, 3]
println(nums.sorted(compareNumbersDesc))
println(nums)
nums.sort(compareNumbersDesc)
println(nums)

入出力結果(Console Output)

1 1 true
1 2 false
1 3 false
1 4 false
1 5 false
2 1 true
2 2 true
2 3 false
2 4 false
2 5 false
3 1 true
3 2 true
3 3 true
3 4 false
3 5 false
4 1 true
4 2 true
4 3 true
4 4 true
4 5 false
5 1 true
5 2 true
5 3 true
5 4 true
5 5 true
[5, 4, 3, 2, 1]
[5, 1, 4, 2, 3]
[5, 4, 3, 2, 1]
Program ended with exit code: 0