Thanks to you both for this extensive proposal. It contains many utility procedures that I would certainly find useful in my code. I have a few minor comments and questions (as a reader, not in my capacity as editor):

1. I don't understand this:


  (hash-table-set!

hash-table ( key value ) ...)

In particular, I don't understand the inner parentheses. Is this a macro?

2.  What's the reasoning for having some procedures take multiple keys as separate arguments and others take them together as a list?

(hash-table-set-entries! hash-table keys-list values-list)

(hash-table-delete! hash-table key ...)

  (hash-table-delete-keys! hash-table keys-list)
The former doesn't seem useful, and having both makes the API confusing.

3. In this description:

  (hash-table-extend!/default hash-table key default)
"Effectively invokes hash-table-ref/default with the given arguments and returns what it returns. If key was not found in hash-table, its association is set to the result being returned. Must execute in expected amortized constant time."
Doesn't it set the association's value to default in that case?
Similarly for:
  (hash-table-replace! hash-table key [ failure [ success ] ])

and:
  (hash-table-replace!/default hash-table key default)

4. The word "hash-table" appears immediately above the section header "Copying and conversion," apparently by accident.