From: Michael Sung <lists@...>
Date: 2012-06-12T00:18:48+09:00
Subject: Chris Pine "Learning Programming" Question

I'm still going through Chris Pine's book on Ruby programming and came
across the following exercise.  To put it simply, I just don't
understand how this code works.


def englishNumber number
  #  We only want numbers from 0-100.
  if number < 0
    return 'Please enter a number zero or greater.'
  end
  if number > 100
    return 'Please enter a number 100 or lesser.'
  end

  numString = ''  #  This is the string we will return.

  #  "left" is how much of the number we still have left to write out.
  #  "write" is the part we are writing out right now.
  #  write and left... get it?  :)
  left  = number
  write = left/100          #  How many hundreds left to write out?
  left  = left - write*100  #  Subtract off those hundreds.

  if write > 0
    return 'one hundred'
  end


QUESTION 1: For example, if I choose 99 as my number, left = number, and
write = left/100, wouldn't write = 99/100?  In that case, why would
write > 0 return 'one hundred'?


write = left/10          #  How many tens left to write out?
  left  = left - write*10  #  Subtract off those tens.

  if write > 0
    if write == 1  #  Uh-oh...
      #  Since we can't write "tenty-two" instead of "twelve",
      #  we have to make a special exception for these.
      if    left == 0
        numString = numString + 'ten'
      elsif left == 1
        numString = numString + 'eleven'
      elsif left == 2
        numString = numString + 'twelve'
      elsif left == 3
        numString = numString + 'thirteen'
      elsif left == 4
        numString = numString + 'fourteen'
      elsif left == 5
        numString = numString + 'fifteen'
      elsif left == 6
        numString = numString + 'sixteen'
      elsif left == 7
        numString = numString + 'seventeen'
      elsif left == 8
        numString = numString + 'eighteen'
      elsif left == 9
        numString = numString + 'nineteen'
      end
      #  Since we took care of the digit in the ones place already,
      #  we have nothing left to write.
      left = 0
    elsif write == 2
      numString = numString + 'twenty'
    elsif write == 3
      numString = numString + 'thirty'
    elsif write == 4
      numString = numString + 'forty'
    elsif write == 5
      numString = numString + 'fifty'
    elsif write == 6
      numString = numString + 'sixty'
    elsif write == 7
      numString = numString + 'seventy'
    elsif write == 8
      numString = numString + 'eighty'
    elsif write == 9
      numString = numString + 'ninety'
    end

    if left > 0
      numString = numString + '-'
    end
  end

  write = left  #  How many ones left to write out?
  left  = 0     #  Subtract off those ones.

  if write > 0
    if    write == 1
      numString = numString + 'one'
    elsif write == 2
      numString = numString + 'two'
    elsif write == 3
      numString = numString + 'three'
    elsif write == 4
      numString = numString + 'four'
    elsif write == 5
      numString = numString + 'five'
    elsif write == 6
      numString = numString + 'six'
    elsif write == 7
      numString = numString + 'seven'
    elsif write == 8
      numString = numString + 'eight'
    elsif write == 9
      numString = numString + 'nine'
    end
  end

  if numString == ''
    #  The only way "numString" could be empty is if
    #  "number" is 0.
    return 'zero'
  end

  #  If we got this far, then we had a number somewhere
  #  in between 0 and 100, so we need to return "numString".
  numString
end

QUESTION 2: The second part of this code is just plain confusing me,
perhaps because I still can't figure out the first part which it builds
upon.

Any clarification & help would be greatly appreciated.

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