METHINKS IT IS LIKE A WEASEL

cf. どう書く？org - METHINKS IT IS A WEASEL

ずいぶん前に「ブラインドウォッチメイカー」を読んだ書いてみたもの。出遅れだし，お題ともちょっと違うので投稿せずにここにさらしておく。

 
 IDEAL = "METHINKS IT IS LIKE A WEASEL"
 
 class Individual
   def initialize(phenotype)
     @phenotype = phenotype.upcase
   end
 
   attr_reader :phenotype
 
   def delivery
     next_phenotype = @phenotype.dup
     next_phenotype[rand(@phenotype.size)] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ ".slice(ra nd(27), 1)
     Individual.new(next_phenotype)
   end
 
   def breed(n)
     next_generation = []
     n.times do
       next_generation << delivery
     end
     next_generation
   end
 
   def to_s
     @phenotype
   end
 end
 
 class Nature
   def initialize(ideal)
     @ideal = ideal
   end
 
   def select(group)
     r = []
     max = 0
     group.each do |i|
       s = evaluate(i)
       if s > max
         max = s
         r = [i]
       elsif s == max
         r << i
       end
     end
     r[0]
   end
 
   def evaluate(ind)
     phenotype = ind.phenotype
     score = 0
     0.upto(@ideal.size - 1) do |i|
       score += 1 if phenotype[i] == @ideal[i]
     end
     score
   end
 end
 
 
 if __FILE__ == $0
 
 require 'optparse'
 
 def err_exit(msg)
   $stderr.print msg
   exit
 end
 
 options = {:number => 100}
 opts = OptionParser.new
 opts.banner = "Usage: ruby miilaw.rb [option] initial\n"
 opts.on_tail('-h', '--help', 'show this massage.') {puts opts; exit(0)}
 opts.on('-n', '--number=NUM', Integer, 'set number of children.') {|options[:numbe r]|}
 opts.parse!
 
 err_exit(opts.help) if ARGV.empty?
 
 len = IDEAL.size
 init = ARGV.shift.upcase
 if init.size < len
   init = "%-#{len}s" % init
 elsif init.size > len
   init = init[0,len]
 end
 
 individual = Individual.new(init)
 nature = Nature.new(IDEAL)
 
 genaration = 0
 print "#{genaration} : #{individual}\n"
 while true do
   genaration += 1
   next_gen = individual.breed(options[:number])
   individual = nature.select(next_gen)
   print "#{genaration} : #{individual}\n"
   break if individual.phenotype == IDEAL
 end
 
 end