conway.rb

# Cheaty idea
class Conway
  def initialize(height, width)
    @height = height
    @width = width
    @cells = [0] * width
  end

  def set_cell(x,y,v) # v is a boolean value
    if v
      @cells[x % @width] |= 1 << y
    else
      @cells[x % @width] ^= 1 << y
    end
  end

  def multicell_state(*array_of_points)
    points = Hash.new
    array_of_points.map do |x,y|
      points[x] ||= []
      points[x].push(y) if y >= 0 and y < @height
    end
    hits = 0
    points.each_pair do |x, y|
      hitmash = @cells[x % @width] & y.reduce(0) {|s,i| s |= 1 << i}
      hits += y.reduce(0) {|s,i| s += 1 if (hitmash & (1<<i)) > 0}
    end
    hits
  end

  def num_neighbors(x,y)
    multicell_state( [x-1, y], [x+1, y], [x,y-1], [x,y+1] )
  end
end


# Test
if __FILE__ == $0
  life = Conway.new(5,5)
  life.set_cell(1,1,true)
  life.set_cell(1,3,true)
  life.set_cell(0,2,true)
  life.set_cell(2,2,true)
  puts life.num_neighbors(1,2) #=> 4
end