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To try to make this concrete, if you have a program A that does bubble sort, and a program B that does selection sort: 1. VBB would be making it so you can't glean information about A or B by running VBB(A) or VBB(B) or examining them, for various definitions of "information". You can't tell A is a bubble sort at all, and you can't tell B is a selection sort at all. VBB is, as mentioned, impossible in the general case. 2. IO would be making it so if you are holding IO(A) and IO(B), you can't tell them apart, and can't tell if the original was A or B. So you can have functionally identical programs, and when you run them through IO, you can't tell whether the original was A or B. |