What do you think?
I didn't read that part of the spec, so I was confused, and I'll grant that
the cases may be out of scope.
Moreover, I think the hash specification is problematic.
(a) the representation seems to wish to hide the current size of the
hash vector, or at least that would be sensible, but it is exposed
in the printout and as an argument to the hash-function supplied to
hashx. The point at which the hash is resized is unpredictable from
the user's point of view. This is three flavors of rep exposure.
(b) if, as the doc says, "it's imperative that just one set is then used
consistently, or results will be unpredictable", then it makes sense
to enforce this. A common way to enforce it is to ask for the hash
function just once, at creation time. By requiring it everywhere,
we force the user to expose a representation, the hash function and
equality predicate, between one part of their program and another.
(c) the assoc requirement is a rep exposure of a third sort -- it exposes
the fact that buckets are alists. There is no reason for the user to
know this, and there is no reason it should be so. If a future
implementation wants to do something else, say hash with another
hash, they will have to emulate assoc-ability to make this API work.
Moreover, this forces the user to write the assoc function on top of
their equality predicate, which is neither fast (it's Scheme instead
of C) nor DRY (Don't Repeat Yourself -- a principle of not
duplicating code).
If the current set of decisions seems self-consistent and useful to the
community, then I guess I'd submit an enhancement request, for a new set of
fast functions:
(make-hashf-table one-arg-hash-function equality-predicate [size])
(hashf-set! hashf-table 'key value)
(hashf-ref hashf-table 'key [default])
(hashf-remove! hashf-table 'key)
(hashf-size hashf-table) ===> the number of keys stored
... [clear get-handle create-handle for-each for-each-handle map->list
"f" for the functions it stores.
Thanks,
Grem
--
------ __@ Gregory A. Marton http://csail.mit.edu/~gremio/
--- _`\<,_ .
-- (*)/ (*) Contents may have settled out of court.
~~~~~~~~~~~~~~~~-~~~~~~~~_~~~_~~~~~v~~~~^^^^~~~~~--~~~~~~~~~~~~~~~++~~~~~~~
