Will Clinger posted to scheme-reports:
In my opinion, the R5RS, R6RS, and R7RS draft 9 all err when they say eq? is an equivalence predicate without alluding to the restricted domain of values for which it is an equivalence predicate.
John Cowan replied that eqv? is also an equivalence predicate only for a limited domain of Scheme values, because it doesn't work on operationally equivalent but unrelated procedures, and asked for a precise definition of "equivalence predicate" that would include eqv? but exclude eq?.