Fix the difference method on bit vectors #4546
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+1, xor is equivalent to the symmetric difference rather the difference |
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This was my fault. Thanks! |
catamorphism
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Fix the difference method on bit vectors
flip1995
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flip1995
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add rust-lang#4546 test changelog: none fixed rust-lang#4546 I notice rust-lang#4546 was fixed some time, I just add the tests.
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I was looking into the
differencemethod on the bit vector implementations, and I found that it didn't quite align with what I thought of as the difference between two sets.For
SmallBitv, the difference was just the xor of the two vectors, which I'm not really sure what it's supposed to represent. ForBigBitv, it almost did the difference except that it added in lots of bits which weren't related to the two bit vectors.I figured that the difference method should return the set-wise difference:
so I updated both of the difference methods to do that and added some tests to do that. If this isn't right, the two implementations (SmallBitv/BigBitv) appear to do different things, so they should probably be unified to one thing anyway.