Close! In math lingo, you can only have a bijective function for domains with equal cardinality. In other words, you couldn't have a bijective function between

Close! In math lingo, you can only have a bijective function for domains with equal cardinality. In other words, you couldn't have a bijective function between an integer and a boolean, because there are fewer possible boolean values than integer values. Demanding bijective functions is probably more restrictive than you want to be for building real-world systems. We discuss this a bit in the paper -- I think look for "convert".