(0) The indirection tax is not fine. I want both nice abstractions and efficient implementations. (1) and (2) Your proposal doesn't work, because different abs

(0) The indirection tax is not fine. I want both nice abstractions and efficient implementations. (1) and (2) Your proposal doesn't work, because different abstract data types are, well, different, even if they expose the same operations. (Perhaps you're confusing “abstract data types” with “abstract classes”?) If you don't believe me, try merging a binomial heap and a pairing heap.