Game of life bit twiddling

golbits.rb

=begin
........ 0x00
........ 0x00
..XX.... 0x30
..XX.... 0x30
....XX.. 0xC0
....XX.. 0xC0
........ 0x00
........ 0x00
=end

world = [0x00, 0x00, 0x30, 0x30, 0x0C, 0x0C, 0x00, 0x00]

def next_generation(world)
  new_world = []
  8.times do |i|
    new_world[i] ||= 0x00
    8.times do |j|
      count = neighbor_count(world, i, j)
      if (alive?(world, i, j) && count == 2) || (count == 3)
        new_world[i] |= (0x80 >> j)
      end
    end
  end
  new_world
end

def neighbor_count(world, i, j)
  count_before = hamming((world[i-1] || 0) & ((0xE0 >> (j-1)) & 0xFF))
  count_current = hamming((world[i] || 0) & ((0xA0 >> (j-1)) & 0xFF))
  count_after = hamming((world[i+1] || 0) & ((0xE0 >> (j-1)) & 0xFF))
  count_before + count_current + count_after
end

def alive?(world, i, j)
  (world[i] & (0x80 >> j)) != 0
end

def hamming(byte)
  dist = 0
  val = byte ^ 0
  while not val.zero?
    dist += 1
    val &= val - 1
  end
  dist
end

def display(world)
  world.each {|row| puts sprintf("%08b", row)}
end

while(true)
  system 'clear'
  display(world)
  world = next_generation(world)
  sleep(3)
end