Swift - Repeating Code Using Loops(if/else, nest, random number(arc4random function), Array extension, Indexing (negative number, indexAt method))

The Swift Programming Language
Apple Inc.

開発環境

• OS X Mavericks - Apple(OS)
• Xcode 6.0 Beta 6
• Swift (プログラミング言語)

Practical Programming: An Introduction to Computer Science Using Python 3 (Pragmatic Programmers) (Paul Gries (著)、Jennifer Campbell (著)、Jason Montojo (著)、Lynn Beighley (編集)、Pragmatic Bookshelf)のChapter 9(Repeating Code Using Loops)、9.10(Exercises) 8-a, b, c.をSwiftで考えてみる。

9.10(Exercises) 8-a, b, c.

コード(Xcode)

main.swift

//
//  main.swift
//  sample8
//
//  Created by kamimura on 9/10/14.
//  Copyright (c) 2014 kamimura. All rights reserved.
//

import Foundation

func makeRandArray() -> [UInt32] {
    var result:[UInt32] = []
    for x in 0..<9 {
        result.append(arc4random() % 10 + 1)
    }
    return result
}

let rat_1 = makeRandArray()
let rat_2 = makeRandArray()


println("rat_1 = \(rat_1)")
println("rat_2 = \(rat_2)")

println("a.")
if rat_1[0] > rat_2[0] {
    println("Rat 1 weighed more than Rat 2 on day 1.")
} else {
    println("Rat 1 weighed less than Rat 2 on day 1.")
}

println("b.")
if rat_1[0] > rat_2[0] && rat_1.indexAt(-1) > rat_2.indexAt(-1) {
    println("Rat 1 remained heavier than Rat 2.")
} else {
    println("Rat 2 became heavier than Rat 1.")
}

println("c.")
if rat_1[0] > rat_2[0] {
    if rat_1.indexAt(-1) > rat_2.indexAt(-1) {
        println("Rat 1 remained heavier than Rat 2.")
    } else {
        println("Rat 2 became heavier than Rat 1.")
    }
} else {
    println("Rat 2 became heavier than Rat 1.")
}

array.swift

//
//  array.swift
//  array
//
//  Created by kamimura on 8/21/14.
//  Copyright (c) 2014 kamimura. All rights reserved.
//

import Foundation

extension Array {
    func indexAt(i:Int) -> T {
        if i >= 0 {
            return self[i]
        }
        let new_index:Int = self.count + i
        return self[new_index]
    }
    func slice(start:Int = 0, end:Int? = nil) -> Array {
        var new_start = start >= 0 ? start : self.count + start
        var new_end:Int
        if end == nil {
            new_end = self.count
        } else if end! >= 0 {
            new_end = end!
        } else {
            new_end = self.count + end!
        }
        var result:Array = []
        if new_start >= new_end {
            return []
        }
        for i in new_start..<new_end {
            result.append(self[i])
        }
        return result
    }
    func forEach(f:(T) -> ()) {
        for e in self {
            f(e)
        }
    }
}

func sum(nums:[Int]) -> Int {
    return nums.reduce(0, combine: {(x, y) in x + y})
}

入出力結果(Console Output)

$ ./sample8 
rat_1 = [2, 7, 1, 1, 6, 2, 5, 6, 2]
rat_2 = [7, 9, 5, 3, 7, 10, 6, 1, 3]
a.
Rat 1 weighed less than Rat 2 on day 1.
b.
Rat 2 became heavier than Rat 1.
c.
Rat 2 became heavier than Rat 1.
$ ./sample8 
rat_1 = [3, 6, 8, 8, 5, 9, 4, 4, 8]
rat_2 = [9, 3, 2, 10, 10, 10, 3, 9, 3]
a.
Rat 1 weighed less than Rat 2 on day 1.
b.
Rat 2 became heavier than Rat 1.
c.
Rat 2 became heavier than Rat 1.
$ ./sample8 
rat_1 = [1, 9, 1, 3, 2, 8, 5, 2, 5]
rat_2 = [3, 8, 8, 1, 2, 10, 7, 8, 5]
a.
Rat 1 weighed less than Rat 2 on day 1.
b.
Rat 2 became heavier than Rat 1.
c.
Rat 2 became heavier than Rat 1.
$ ./sample8 
rat_1 = [1, 7, 1, 6, 6, 4, 3, 9, 10]
rat_2 = [2, 8, 6, 1, 10, 10, 4, 6, 4]
a.
Rat 1 weighed less than Rat 2 on day 1.
b.
Rat 2 became heavier than Rat 1.
c.
Rat 2 became heavier than Rat 1.
$ ./sample8 
rat_1 = [9, 9, 6, 2, 2, 4, 2, 9, 1]
rat_2 = [7, 2, 8, 3, 9, 7, 9, 1, 2]
a.
Rat 1 weighed more than Rat 2 on day 1.
b.
Rat 2 became heavier than Rat 1.
c.
Rat 2 became heavier than Rat 1.
$