Conway's Game of Life written in Ruby, except classes; ported from https://gist.github.com/thara/ded6dd880ba95580088ef8875abb05e5

lifegame.rb

require 'set'

def neighbors(point)
  return to_enum(:neighbors, point).to_a unless block_given?
  x, y = point
  yield [x + 1, y]
  yield [x - 1, y]
  yield [x, y + 1]
  yield [x, y - 1]
  yield [x + 1, y + 1]
  yield [x + 1, y - 1]
  yield [x - 1, y + 1]
  yield [x - 1, y - 1]
end

def living?(point, board)
  count = neighbors(point).count(&->(n) { board.include? n })
  count == 3 || (count == 2 && board.include?(point))
end

def advance(board)
  recalc = board | board.flat_map(&->(x) { neighbors(x) }).to_set
  recalc.filter(&->(p) { living?(p, board) }).to_set
end

def print_board(state)
  10.times.each do |x|
    10.times.each do |y|
      mark = state.include?([x, y]) ? '*' : '-'
      print mark
    end
    print "\n"
  end
end

state = Set.new([[0, 1], [1, 2], [2, 0], [2, 1], [2, 2]])
print_board(state)
100.times.each do |_|
  gets
  print "\033[11A\r"
  state = advance(state)
  print_board(state)
end