On Sun, Jul 23, 2017 at 10:43 AM, Marc Nieper-Wißkirchen <xxxxxx@nieper-wisskirchen.de> wrote:

When mappings with different comparators are compared, it is an
error if the implementation's default comparator doesn't compare
comparators using <code>eq?</code> as the equality predicate and
doesn't provide a compatible ordering procedure or hash function, respectively.
(If an implementation's
default comparator doesn't handle comparators, an implementation of
this SRFI may still provide its own ordering of comparators.)

Aside from eq?, I think it is still overspecifying:

What about: "... doesn't compare comparators using an equality predicate at least as fine as <code>equal?</code>..."?

How about cutting the Gordian knot and leaving mapping=? alone, and adding a new predicate `mapping-equivalent?` that accepts both a key and a value comparator, and compares two mappings for equivalence based on them? That seems much more Schemely to me than providing a narrow special case in which mixed-comparator tests for equality will work.

John Cowan http://vrici.lojban.org/~cowan xxxxxx@ccil.org

Objective consideration of contemporary phenomena compel the conclusion

that optimum or inadequate performance in the trend of competitive

activities exhibits no tendency to be commensurate with innate capacity,

but that a considerable element of the unpredictable must invariably be

taken into account. --Ecclesiastes 9:11, Orwell/Brown version