The current draft states:

  The library (srfi 146) described in this SRFI requires comparators

  to provide a comparison function.

I'm guessing this means the ordering predicate, and that the equality

predicate is not required/used, so that key equality is effectively

determined by

  (and (not (less? key1 key2)) (not (less? key2 key1)))

?  It's worth making this explicit.

I assume for mapping-adjoin, the previous key object is preserved.

For mapping-set/replace/intern/update we should state what the

behavior is, even if that behavior is unspecified.  Note in SRFI 113,

set/bag-replace specify that the new key object is used.

--