Conway's Game of Life

gol.rb

#!/usr/bin/ruby

seed = <<eos
..........
..........
..#.......
...#......
...##.....
...##.....
....#.....
.....#....
......#...
..........
eos

class Matrix
  def initialize(matrix)
    @m = matrix
  end
  
  def self.from_seed(seed)
    Matrix.new(seed.strip.split("\n").map { |row| row.split '' })
  end
  
  def next
    (0...rows).map do |y|
      (0...cols).map do |x|
        type_after_tick(x, y)
      end
    end.to_matrix
  end
  
  def type_after_tick(x, y)
    count = count_alive(x, y)
    return '#' if count == 4 && self[x, y].alive?
    count == 3 ? '#' : '.'
  end
  
  # count of alive cells in 3x3 matrix around given center
  def count_alive(cx, cy)
    (cx-1..cx+1).map do |x|
      (cy-1..cy+1).map do |y|
        self[x, y].alive? ? 1 : 0
      end
    end.flatten.reduce(:+)
  end
  
  def [](x, y)
    # wrap to torus surface using modulo arithmetics and the fact that
    # a[-n] == a[a.length-n]
    @m[y%10][x%10]
  end

  def rows
    @m.count
  end
  
  def cols
    @m.first.count
  end
  
  def to_s
    @m.map(&:join).join "\n"
  end
  
end

class String
  def alive?
    self == '#'
  end
end

class Array
  def to_matrix
    Matrix.new self
  end
end

Signal.trap 'INT' do
  clear_and_home
  exit
end

def clear_and_home
  puts "\e[1J" # clear terminal up to cursor position
  puts "\e[H"  # move cursor to upper left corner
end

matrix = Matrix.from_seed(seed)

while true
  clear_and_home
  puts matrix.to_s
  matrix = matrix.next
  sleep 0.1
end