# -*- coding: utf-8 -*-
def reset
  callcc do |c|
    old_mc = Thread.current[:mc]
    Thread.current[:mc] = lambda do |v|
      Thread.current[:mc] = old_mc
      c.call(v)
    end
    v = yield
    Thread.current[:mc].call(v)
  end
end

def shift
  callcc do |c|
    v = yield(lambda do |v2|
                reset do c.call(v2) end
              end)
    Thread.current[:mc].call(v)
  end
end

def procedure
  proc do |*args|
    cur_c = reset do
      yield
    end
    args.each do |arg|
      cur_c = cur_c.call(arg)
    end
    cur_c
  end
end

def _
  shift do |c|
    c
  end
end

hello = procedure do
  puts("Hello #{_}, I am #{_}.")
end

hello.call('Rubyists', 'a novice Haskeller')
hello.call('Haskellers', 'a novice Rubyist')