turing-pattern.rb

turing-pattern.rb

#!/usr/bin/env ruby
# cf. https://researchmap.jp/blogs/blog_entries/view/76000/82ceec6feab77462a8f9598c65815d76

NX = 32
NY = 32
NT = 20
W1 = 1
W2 = 1

@world = nil

def display
  puts "----"
  NY.times do |y|
    NX.times do |x|
      if on(x, y)
        print "●"
      else
        print "○"
      end
    end
    puts
  end
end

def on(x, y)
  if x < 0 or y < 0 or NX <= x or NY <= y
    false
  else
    @world[y][x]
  end
end

def count_adjacents(x, y)
  count = 0
  count += 1 if on(x - 1, y)
  count += 1 if on(x, y - 1)
  count += 1 if on(x + 1, y)
  count += 1 if on(x, y + 1)
  count
end

def count_neibors(x, y)
  count = 0
  count += 1 if on(x - 2, y)
  count += 1 if on(x, y - 2)
  count += 1 if on(x + 2, y)
  count += 1 if on(x, y + 2)
  count += 1 if on(x - 1, y - 1)
  count += 1 if on(x + 1, y - 1)
  count += 1 if on(x - 1, y + 1)
  count += 1 if on(x + 1, y + 1)
  count
end

def next_generation
  next_world = []
  NY.times do |y|
    next_world[y] = []
    NX.times do |x|
      ev = W1 * count_adjacents(x, y) - W2 * count_neibors(x, y)
      if ev > 0
        next_world[y][x] = true
      elsif ev < 0
        next_world[y][x] = false
      else
        next_world[y][x] = @world[y][x]
      end
    end
  end
  @world = next_world
end

def init_world
  srand(314159)
  @world = []
  NY.times do |y|
    @world[y] = []
    NX.times do |x|
      @world[y][x] = [false, true].sample
    end
  end
end

init_world
display
NT.times do
  next_generation
  display
end

https://twitter.com/hyuki/status/1347848936359251968