Question

So I have this hash below:

   a_hash = {
    "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",
    "30" => "thirty",
    "40" => "forty",
    "50" => "fifty",
    "60" => "sixty",
    "70" => "seventy",
    "80" => "eighty",
    "90" => "ninety",
    "00" => "hundred", #not sure this is right 
    "000" => "thousand"  #not sure this is right 

    } 

Lets say my string input is “99100”.
Lets say I want my string output to be “ninty nine thousand one hundred”.
How do I go about using my hash above without typing each key/value. I was thinking maybe split my string at each char into an array….then for each number in that array return my value? Any other stratgies I should consider? This is what I have so far:

  puts "test the hash! Type a number hit enter"
  test_variable = gets.to_s.chomp
  puts a_hash[test_variable]

Post some code so I can try out. Thanks!

Answer 1

Short answer: don’t do this yourself, find a library that does it for you.

However, it can be a cool exercise and it is actually an interesting problem. So, ignoring best practices of not reinventing the wheel… You’ll probably have to treat hundreds and thousands differently, because you can say “two hundred”, but “two seventy” doesn’t really make much sense.

Here’s my poorly-tested, unoptimised attempt. It is a proof-of-concept and I’m pretty sure I have overlooked many cases. If you want more help, try reading other people’s source code.

First we define two hashes, one for numbers, one for magnitudes (which are distinct because they can be prefixed with numbers in order to multiply them).

class Integer
  NUMBERS = {
    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",
    30 => "thirty",
    40 => "forty",
    50 => "fifty",
    60 => "sixty",
    70 => "seventy",
    80 => "eighty",
    90 => "ninety"
  }

  MAGNITUDES = {
    100 => "hundred",
    1000 => "thousand",
    1000_000 => "million"
  }
end

Next, define the conversion method.

class Integer
  def to_text
    return nil if self == 0
    if NUMBERS.keys.include? self
      NUMBERS[self]
    elsif self < MAGNITUDES.keys.first
      base = maximum_fitting(NUMBERS, self)
      [NUMBERS[base], (self - base).to_text].compact * "-"
    else
      base = maximum_fitting(MAGNITUDES, self)
      quo, mod = self.divmod(base)
      [quo.to_text, MAGNITUDES[base], mod.to_text].compact * " "
    end
  end

  private

  def maximum_fitting(list, number)
    list.keys.select { |n| n <= number }.last
  end
end

To use it:

puts 2351.to_text
#=> "two thousand three hundred fifty-one"

puts 14330132.to_text
#=> "fourteen million three hundred thirty thousand one hundred thirty-two"

puts 1000000.to_text
#=> "one million"