Ported from Wibit.net objective-c implementation

mersenne_twister.rb

@_MT = Array.new
@_index = 0
@maskUnity = 0xffffffff # 32 bits
@maskHighestBit = 0x80000000 # Most significant bit;
@maskLowerBits = 0x7fffffff # Last 32 bits

def initializeGenerator seed
  # Set first array value to be the seed
  @_MT[0] = seed
  1.upto(623) do |i|
    @_MT[i] = @maskUnity & (1812433253 * (@_MT[i - 1] ^ (@_MT[i - 1] >> 30)) + i);
  end
end

def generateNumbers
  counter = 1
  0.upto(@_MT.size - 2) do |i|
    pieceOfClay = (@maskHighestBit & @_MT[i]) + (@maskLowerBits & (@_MT[i + 1] % 624))    
    tempIndex = (i + 397) % 624
    @_MT[i] = @_MT[tempIndex] ^ (pieceOfClay >> 1)
    if pieceOfClay % 2 != 0
      @_MT[i] = @_MT[i] ^ (0x9908b0df)
    end
  end
end

def extractNumber
  unless @_index != 0
    generateNumbers
  end
  tinyDancer = @_MT[@_index]
  # 11 steps to the right
  tinyDancer = tinyDancer ^ (tinyDancer >> 11)
  # 7 to the left and JUMP 2x
  tinyDancer = tinyDancer ^ ((tinyDancer << 7) & (0x9d2c5680))
  # and then back to the right, and 18 bits, with a hand on the hip
  tinyDancer = tinyDancer ^ ((tinyDancer << 15) & (0xefc60000))
  tinyDancer = tinyDancer ^ (tinyDancer >> 18)
  # and then repeat
  @_index = (@_index + 1) % 624
  return tinyDancer
end

initializeGenerator (Time.now.to_i * 1000).to_i
puts "Your random number is #{extractNumber}\n"