# Expanded version for better readability.
#
life = lambda do |grid, size|
  (0..size*size-1).map do |i|
    lambda do |neighbours|
      neighbours == 3 || ( grid[i] && neighbours == 2 )|| nil
    end.call (
      [
        grid[i-size-1], grid[i-size], grid[i-size+1],
        grid[i-1],                    grid[i+1],
        grid[i+size-1], grid[i+size], grid[i+size+1]
      ].compact.count
    )
  end
end