tapcode.rb

#!/usr/bin/env ruby -wKU
# http://en.wikipedia.org/wiki/Quadratic_alphabet_code

require 'pp'

class TapCode
  
  attr_reader :letters, :array
  
  def initialize
    # build array of letters
    @letters = ('A'..'Z').to_a - ['K']

    # this array will store chunks of 5 letters
    @array = []

    # split the array of letters into chunks of 5
    size = 5
    0.upto(size-1) do |n|
      start     = n*size
      finish    = start+size-1
      @array[n] = @letters[(start..finish)]
    end
  end

  # method to look up a letter and convert it to the Tap Code
  def lookup(letter)
    @array.map{|a| a.index(letter.upcase) }.each_with_index do |column,row|
      
      # each of these looks is an array of size 5... i.e.
      # D => [3, nil, nil, nil, nil]
      # N => [nil, nil, 2, nil, nil]
      # Z => [nil, nil, nil, nil, 4]
      
      next if column.nil?
      return "#{'.'*(row+1)} #{'.'*(column+1)}"
    end

    # anything else (like a space) is nil
    return nil
  end

  # method to convert a string to a series of taps
  def encode(message)
    message.sub(/ /,'').split('').inject(""){|s,l| s + lookup(l) + " "}
  end
  
  # TODO: decode() method

end

if $0 == __FILE__
  
  tap = TapCode.new
  
  # print the array
  pp tap.array

  # print the mapping for each letter
  tap.letters.each do |letter|
    puts letter + ": " + tap.lookup(letter)
  end

  puts "hello world: " + tap.encode("hello world")
end