#!/usr/koeki/bin/ruby
# coding: euc-jp



premise = Hash.new

subject = "人間"
object = "いつか死ぬ"

premise[subject] = object

subject2 = "ソクラテス"
object2 = subject

premise[subject2] = object2

#p premise

if premise.value?(subject) == true
  printf("%sは%s\n", subject, premise[subject])
  printf("%sは%s\n", subject2, premise[subject2])
  printf("ゆえに%sは%s\n", subject2, premise[premise[subject2]])
end