pattern-match.rb

#!/usr/bin/env ruby

class Matcher
  def initialize( *args, &blk )
    @args = args
    @blk = blk
  end

  def call( *params )
    matches = @args.zip(params).all?{|arg, param|
      arg.nil? || arg === param
    }
    @blk.call if matches
  end

end


module Kernel
  def pattern( *args, &blk )
    $MATCHERS=[]
    yield
    $MATCHERS.each do |matcher| 
      result = matcher.call( *args )
      return result if result
    end
  end

  def match( *args, &blk )
    $MATCHERS << Matcher.new( *args, &blk )
  end

  def _; nil; end
end


(1..100).each do |i|
  puts pattern(i%3, i%5) {
    match(0,0){ "FizzBuzz" }
    match(0,_){ "Fizz" }
    match(_,0){ "Buzz" }
    match(_){ i }
  }
end