patterndemo.rb

require 'pp'
class PatternObject
  def initialize
    @patterns = Hash.new
  end
  def method_missing(name, *args)
    candidates = @patterns[name]
    winner = candidates.detect do |c|
      c.match args
    end
    raise 'aaaaaa' unless winner
    winner.invoke args
  end

  def pattern(function_name, *options, &block)
    @patterns[function_name] ||= []
    @patterns[function_name] << Pattern.new(options, block)
  end
end

class Pattern
  def initialize(options, block)
    @options = options
    @block = block
  end

  def invoke(args)
    @block.call *args
  end

  def match(args)
    @options.zip args do |o, a|
      return false unless o === a
    end
    return true
  end
end

zzz = PatternObject.new
zzz.pattern :asdf, Fixnum, /bra+ins/ do
  puts "i'ma  zombie arrrrr"
end

zzz.pattern :asdf, Fixnum, String do
  puts 'called with fixnum and string'
end

zzz.pattern :asdf, Fixnum, Fixnum do
  puts 'called with two fixnums'
end