ruby 1.7 feature:
Ƥʤ᥽åɤθƤӽФԤ줿Ȥȯޤ

        self.bar
        => -:1: undefined method `bar' for #<Object:0x401a6c40> (NoMethodError)

᥽åɸƤӽФηǤʤ NameError 㳰ȯޤ

        bar
        => -:1: undefined local variable or method `bar' for #<Object:0x401a6c40> (NameError)