Ruby - 再帰(数値を英文に変換)

初めてのプログラミング 第2版
Chris Pine (著) 長尾 高弘 (訳)

開発環境

• OS X Lion - Apple(OS)
• TextWrangler(Text Editor) (BBEditの機能制限無料版、light版)
• Script言語:Ruby

『初めてのプログラミング 第2版』(Chris Pine　著、長尾 高弘　訳、オライリー・ジャパン、2010年、ISBN978-4-87311-469-9)の 10(章全部で復習), 10.5(練習問題の続き)、拡張 english_number を解いてみる。

その他参考書籍

• 『プログラミング言語 Ruby』David Flanagan, まつもと ゆきひろ　著 、卜部 昌平　監訳、長尾 高弘　訳、オライリー・ジャパン、2009年、ISBN978-4-87311-394-4)
• Rubyクックブック ―エキスパートのための応用レシピ集

拡張 english_number

コード(TextWrangler)

sample.rb

#!/usr/bin/env ruby
# -*- coding: utf-8 -*-

def english_number number
  return '0以上の数値を入力してください。' if number < 0
  return 'zero' if number == 0
  result = ''
  ones_place = ['one', 'two', 'three',
                'four', 'five', 'six',
                'seven', 'eight', 'nine']
  tens_place = ['ten', 'twenty', 'thirty',
                'forty', 'fifty', 'sixty',
                'seventy', 'eighty', 'ninety']
  teenagers = ['eleven', 'twelve', 'thirteen',
               'fourteen', 'fifteen', 'sixteen',
               'seventeen', 'eighteen', 'nineteen']
  others = [['hundred',2],
            ['thousand',3],
            ['million',6],
            ['billion',9],
            ['trillion',12]]
  
  left = number
  while others.length > 0
    other = others.pop
    write = left / (10 ** other[1])
    left = left - write * (10 ** other[1])
    if write > 0
      hundreds = english_number write
      result = result + hundreds + ' ' + other[0]
      if left > 0
        result += ' '
      end
    end
  end
  write = left / 10
  left = left - write * 10
  if write > 0
    if (write == 1) and (left > 0)
      result += teenagers[left - 1]
      left =0
    else
      result += tens_place[write - 1]
    end
    result += '-' if left > 0
  end
    
  write = left
  left = 0
  
  if write > 0
    result += ones_place[write-1]
  end
  
  result
end

(-1..100).each do |number|
  puts "#{number}: #{english_number number}"
end

number = 1_234_567_890
puts "#{number}: #{english_number number}"

入出力結果(Terminal)

$ ./sample.rb
-1: 0以上の数値を入力してください。
0: zero
1: one
2: two
3: three
4: four
5: five
6: six
7: seven
8: eight
9: nine
10: ten
11: eleven
12: twelve
13: thirteen
14: fourteen
15: fifteen
16: sixteen
17: seventeen
18: eighteen
19: nineteen
20: twenty
21: twenty-one
22: twenty-two
23: twenty-three
24: twenty-four
25: twenty-five
26: twenty-six
27: twenty-seven
28: twenty-eight
29: twenty-nine
30: thirty
31: thirty-one
32: thirty-two
33: thirty-three
34: thirty-four
35: thirty-five
36: thirty-six
37: thirty-seven
38: thirty-eight
39: thirty-nine
40: forty
41: forty-one
42: forty-two
43: forty-three
44: forty-four
45: forty-five
46: forty-six
47: forty-seven
48: forty-eight
49: forty-nine
50: fifty
51: fifty-one
52: fifty-two
53: fifty-three
54: fifty-four
55: fifty-five
56: fifty-six
57: fifty-seven
58: fifty-eight
59: fifty-nine
60: sixty
61: sixty-one
62: sixty-two
63: sixty-three
64: sixty-four
65: sixty-five
66: sixty-six
67: sixty-seven
68: sixty-eight
69: sixty-nine
70: seventy
71: seventy-one
72: seventy-two
73: seventy-three
74: seventy-four
75: seventy-five
76: seventy-six
77: seventy-seven
78: seventy-eight
79: seventy-nine
80: eighty
81: eighty-one
82: eighty-two
83: eighty-three
84: eighty-four
85: eighty-five
86: eighty-six
87: eighty-seven
88: eighty-eight
89: eighty-nine
90: ninety
91: ninety-one
92: ninety-two
93: ninety-three
94: ninety-four
95: ninety-five
96: ninety-six
97: ninety-seven
98: ninety-eight
99: ninety-nine
100: one hundred
1234567890: one billion two hundred thirty-four million five hundred sixty-seven thousand eight hundred ninety
$