Thank you for your valuable comments!

Sudarshan S Chawathe <xxxxxx@eip10.org> schrieb am Do., 10. Aug. 2017 um 05:10 Uhr:

I enjoyed reading this SRFI very much. Below are a few comments, mostly
minor [Ref. "Draft #2 published: 2017/7/29"].

- In the test-tail-position example, should the "tail"s in the
let-syntax be "tail?"s?

I changed all occurrences of ‘tail?’ into ‘tail’.

- with-continuation-mark: I am not sure whether there is supposed to
be an ordering in the evaluation of <key> and <value>. I would
guess not, but an explicit statement either way would be helpful.

The Racket version evaluates ‘key’ and ‘value’ in order. This was also the intended meaning of my wording, which includes the adverb "finally" suggesting an order. I could add an "In order, ..." at the beginning of the sentence if you think this would make it clearer.

- In continuation-mark-set->list*, perhaps the fixed value of #f to
indicate a missing value for a mark could be replaced with a more
general default, similar to what is used for hash tables in SRFI 69,
etc. (so that programs may easily use #f as a mark's value). A
similar comment applies to continuation-mark-set-first and
call-with-immediate-continuation-mark.

Racket provides such default values. I stripped it down for simplicity so that SRFI 157 mainly includes the core concepts. You can still use #f as a mark's value as follows:

(with-continuation-mark <key> #f (with-continuation-mark 'dummy #t ...))

In ... you can then in (continuation-mark-set->list* <marks> '(<key> dummy)) whether #t shows up in the dummy slot.

Have you taken a look at the more general Racket procedures? If you think it is worthwhile I am adding default values to SRFI 157.

- In the sample implementation, file lib/inferior/expression.scm, the
four definitions immediately following the comment "Named let" are
duplicated.

Thanks! Copy and paste error.

- In the sample implementation, file lib/inferior/unspecified.scm,
"unspecified?" is used both as a predicate for the "<unspecified>"
record-type and as a name for a separately defined procedure. I am
not sure if this is allowed by R7RS. (Kawa complains, but Larceny
does not, in my very limited testing.)

Thanks! Fixed.

- Minor points:

- An earlier note that a continuation mark is conceptually a
key-value pair associated with a frame, with keys compared using
eq?, would be helpful (for better understanding of the examples, in
particular).

Added this to the abstract.

- current-continuation-marks: The description mentions
continuation-mark-set->list and continuation-mark-set-first, but not
continuation-mark-set->list*, which seems a bit odd, although the
implication is probably clear enough.

Added.

- Perhaps "continuation-mark-set" could be replace with
"continuation-marks" in the procedure names. I think the latter is
simpler and matches the names "current-continuation-marks" and
"continuation-marks?" better, though I can also see value in
sticking with the names used by Racket.

I agree with you but as long as there is no evidence for another established naming besides the Racket one, I think it is better to remain compatible with Racket.

- (very minor) In the factorial example (which is very nice), a
distinction could perhaps be drawn between "procedures and
processes they generate" (using terminology from the "Structure
and Interpretation of Computer Programs" book) in the context of
recursion v. iteration . Even more minor, the correspondence
between fact1 and fact2 could be made even more obvious by using a
named-let in fact1.

Added the named-let to make it more symmetric. With respect to procedures and processes they generate: Can you write a sentence or two which you like to be added?

Marc

Regards,

-chaw

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