--- values_at(member_1, ... member_n)

    ruby 1.8 feature

    ǻꤵ줿(͡ʸ󤢤뤤 Symbol)ͤ
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    IndexError 뤤 NameError ȯޤ

        Foo = Struct.new(:foo, :bar, :baz)
        obj = Foo.new('FOO', 'BAR', 'BAZ')

        p obj.values_at(0, :bar, 'baz')    # => ["FOO", "BAR", "BAZ"]

