Banal natural selection emulation. Wrote mainly to mess around with terminal manipulation and Win32 bindings.

win32_critters.rb

# ENCODING: UTF-8
# ruby 3.0.3p157 (2021-11-24 revision 3fb7d2cadc) [x64-mingw32]
# THIS SCRIPT WILL INSTALL REQUIRED GEMS IF POSSIBLE.
# irb -I . -r ./main.rb # Ignore this.

def require_gem gemname, requirename = nil
  requirename = gemname if requirename.nil?
  require 'rubygems'
  begin
    gem gemname
  rescue Gem::LoadError
    Gem.install gemname
    gem gemname
  end
  require requirename
end

require 'io/console'
require_gem 'rainbow'
require_gem 'win32-api', 'win32/api'
include Win32

Period = ['-p', '--period'].include?(ARGV[0]) ? ARGV[1].to_i : 0.2
Character = ?@
Column_max = 80
Critter_count = 60 * 12
Predator_count = 5

$footer = "Try #{Rainbow('ruby ./main.rb --period 0').yellow} (or #{Rainbow('-p 0').yellow}) for unlimited speed.\n" +
  "Exit by sending an interrupt signal using #{Rainbow('[Ctrl]+[C]').yellow}."

# Win32 API binding data type legend.
# 'I' (integer)
# 'L' (long)
# 'V' (void)
# 'P' (pointer)
# 'K' (callback)
# 'S' (string)

Get_std_handle = API.new('GetStdHandle', ?I)
Get_console_screen_buffer_info = API.new('GetConsoleScreenBufferInfo', 'IS')
Set_console_cursor_position = API.new('SetConsoleCursorPosition', 'IS')
Get_last_error = API.new('GetLastError')
Get_console_cursor_info = API.new('GetConsoleCursorInfo', 'IS')
Set_console_cursor_info = API.new('SetConsoleCursorInfo', 'IS')

class Critter
  Character = Character
  
  attr_accessor :r, :g, :b, :s
  def initialize(*args)
    if args.empty?
      @s = Character
      rand_c
    elsif args.size == 1
      @s = args[0]
      rand_c
    elsif args.size == 3
      @r, @g, @b, @s = args[0], args[1], args[2], Character
    elsif args.size == 4
      @r, @g, @b, @s = args[0], args[1], args[2], args[4]
    else
      raise ArgumentError
    end
  end
  
  def rand_c
    @r, @g, @b = rand(255), rand(255), rand(255)
    return self
  end
  
  def string
    return Rainbow(@s).fg(@r, @g, @b)
  end
  
  def print
    print string
    return true
  end
end

class Field
  Column_max = Column_max
  
  def initialize(critter_count = Critter_count, predator_count = Predator_count, column_max = Column_max)
    @predator_count = predator_count
    @column_count = (Math.sqrt(critter_count) * 1.5).truncate.clamp(0, column_max)
    @critters = Array.new(critter_count)
    @critters.map!{|critter| Critter.new}
  end
  
  def map! *args
    @critters.map! *args
  end
  
  def each *args
    @critters.each *args
  end
  
  def inject *args, &block
    @critters.inject *args, &block
  end
  
  def string
    buffer = String.new
    column = 0
    @critters.each do |critter|
      if column < @column_count
        # critter.print
        buffer.concat critter.string
        column += 1
      else
        column = 0
        buffer.concat "\n"
        redo
      end
    end
    buffer.concat "\n", $footer, "\n"
    return buffer
  end
  
  def print
    # console_screen_buffer_info = 0.chr * [4, 4, 2, 8, 4].sum
    # raise('GetConsoleScreenBufferInfo → zero!', cause: Exception.new(Get_last_error.call)) if
    #   Get_console_screen_buffer_info.call(Stdout_handle, console_screen_buffer_info).zero?
    # console_screen_buffer_info = console_screen_buffer_info.unpack('a4a4Sa8a4')
    
    # dwSize = console_screen_buffer_info[0].unpack('s2')
    # dwCursorPosition = console_screen_buffer_info[1].unpack('s2')
    # wAttributes = console_screen_buffer_info[2]
    # srWindow = console_screen_buffer_info[3].unpack('s4')
    # dwMaximumWindowSize = console_screen_buffer_info[4].unpack('s2')
    
    STDOUT.sync = false
    STDOUT.goto 0, 0
    STDOUT.write string
    STDOUT.flush
    STDOUT.sync = true
    
    # raise('SetConsoleCursorPosition → zero!', cause: Exception.new(Get_last_error.call)) if
    #   Set_console_cursor_position.call(Stdout_handle, dwCursorPosition).zero?
    return true
  end
  
  def predate
    # probability_space = Array.new
    # self.each do |critter|
    #   (critter.r + critter.g).times{probability_space << critter}
    # end
    # @predator_count.times do
    #   critter = probability_space.sample
    #   critter.rand_c
      # @predated = (defined?(@predated) && !@predated.nil?) ? @predated + 1 : 0
      # @palevo = (defined?(@palevo) && !@palevo.nil?) ? @palevo + (critter.r + critter.g) : 0
      # $footer = "palevo_ratio: #{@palevo.fdiv @predated}" if defined?(@palevo)
    # end
    # # palevo_ratio: 254.745014900298
    
    # Antender's algo.
    lottery_entries = @critters.inject(0){|sum, critter| next (sum + critter.r + critter.g)}
    @predator_count.times do
      winning_ticket = rand(lottery_entries)
      @critters.each do |critter|
        winning_ticket -= critter.r + critter.g
        unless winning_ticket.positive?
          # @predated = (defined?(@predated) && !@predated.nil?) ? @predated + 1 : 0
          # @palevo = (defined?(@palevo) && !@palevo.nil?) ? @palevo + (critter.r + critter.g) : 0
          # $footer = "palevo_ratio: #{@palevo.fdiv @predated}" if defined?(@palevo)
          critter.rand_c
          break
        end
      end
    end
    # # palevo_ratio: 254.45631067961165
    return true
  end
end

class Periodic
  def initialize period
    @period = period
    @timestamp = self.class.time_float
  end
  
  def self.time_float
    time = Time.now
    return time.to_i + time.nsec / 1e9
  end
  
  def remainder
    return @period - (self.class.time_float - @timestamp)
  end
  
  def wait
    sleep(remainder) if remainder.positive?
    @timestamp = self.class.time_float
    return true
  end
end

begin
  Stdout_handle = Get_std_handle.call(-11)
  # $footer << "Stdout_handle: #{Stdout_handle}"
  Field = Field.new
  Sim_turn = Periodic.new Period
  STDOUT.erase_screen 2
  
  # console_cursor_info = 0.chr * [4, 1].sum
  # raise('GetConsoleCursorInfo → zero!', cause: Exception.new(Get_last_error.call)) if
    # Get_console_cursor_info.call(Stdout_handle, console_cursor_info).zero?
  # console_cursor_info = console_cursor_info.unpack('LC')
  # puts dwSize = console_cursor_info[0]
  # puts bVisible = console_cursor_info[1]
  
  raise('SetConsoleCursorInfo → zero!', cause: Exception.new(Get_last_error.call)) if
    Set_console_cursor_info.call(Stdout_handle, [25, 0].pack('IC')).zero?
  
  while Sim_turn.wait
    Field.print
    Field.predate
  end
ensure
  STDOUT.goto 0, 0
  STDOUT.erase_screen 2
  puts $footer
  raise('SetConsoleCursorInfo → zero!', cause: Exception.new(Get_last_error.call)) if
    Set_console_cursor_info.call(Stdout_handle, [25, 1].pack('IC')).zero?
  # exit
end