--- clone
--- dup

    ֥Ȥʣޤ
    clone  freezetaintðۥ᥽åɤʤɤξ
    ޤ᤿ʣdup ϥ֥ȤƤΤߤʣ
    ޤ

    clone  dup ϡ(shallow)ץԡǤ뤳Ȥ
    Ƥ֥ȼȤʣǡ֥Ȥλؤ
    Ƥ(ȤǤʤ)ޤǤʣޤ

    ޤʣ֥ȤФ

      obj.equal?(obj.clone)

    ϰ̤Ωޤ
    

      obj == obj.clone

    ¿ξΩޤ

    true, false, nil, Symbol ֥Ȥʤ
    ʣ褦Ȥ㳰 TypeError ȯޤ

    ruby 1.7 feature:
    version 1.7 ǤϡNumeric ֥Ȥʤ immutable(
    )Ǥ륪֥Ȥʣ褦Ȥ㳰 TypeError ȯ
    ޤ

