On Fri, 20 May 2011, Aaron W. Hsu wrote:

> Indeed, I see no reason why an implementation should not be able to return
> no values when there are no "useful" values to consider, and R6RS moved
> *away* from overspecifying this to allow implementation to return as many
> different values as they felt like doing. I've mentioned before that this
> seems to be a much better thing than to force a single value.
>
> However, the votes came in and R5RS' semantics won out.

I think the R6RS approach here is superior.  It removes a useless postulate
regarding the behavior of portable programs and enlarges the space of conforming
implementations.  In removing this weakness/restriction, it seems to me more
Schemely, in the sense of the first paragraph of the introduction of R7RS.

I think that if R7RS wishes to go to the trouble of reintroducing this rather
useless restriction, it will need to accompany it by some very strong
justification.

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