--- Range.new(first,last[, exclude_end])

    first  last ޤǤϰϥ֥Ȥ֤
    exclude_end ʤнüޤޤʤϰϥ֥Ȥ
    ޤexclude_end άˤϽüޤߤޤ

    ˡåȤ

      first <=> last

    ¹Ԥޤ줬㳰֤硢㳰 ArgumentError ȯ
    ޤ(ruby 1.7 feature: first  Numeric 
    󥹥󥹤ǤФΥåϹԤޤ)

