> On Aug 29, 2019, at 1:24 PM, Kevin Forchione <lyss...@gmail.com> wrote:
> Hi guys,
> I’ve been working for a little while with the idea of being able to pass
> keyword arguments through a function that doesn’t define them. Additionally I
> wanted to allow the “pass-through” function to define its own keywords.
> Additionally didn’t want to have to pre-specify what function might be on the
> receiving end of the call. But finally, if both pass-through and called
> functions define the same keywords I didn’t want to have to differentiate
> between them.
> - This seems to involve some combination of make-keyword-procedure and
> - Since make-keyword-procedure expects a “vanilla” function (one without
> keywords specified) I decided to define a macro that would wrap the function
> in a let that with default bindings for each keyword defined by the
> pass-through. Inside the function I would then assign any values provided by
> the function call to those variables.
> - Additionally I would build a parameterized list of keywords defined by the
> pass-through chain. These would be used in conjunction with the keyword list
> produced by procedure-keywords and the keywords/values captured by the
> function call to “filter” the lists used by keyword-apply. The idea being to
> eliminate any keyword/values supplied to the pass-through and defined by the
> pass-through that were not defined by the called function. This would allow
> keywords not defined by either to be error by the called function.
> As you can see, it’s a convoluted approach and I’m not sure how robust it
> actually. I’m presenting working code (for my test cases…) but also wondering
> if someone hasn’t already crated that wheel. :)
A little syntactic sugar makes it appear more palatable with the addition of:
(define-syntax (keyword-apply/filter stx)
[(_ fn kw kv args)
(define-values (rkw akw) (procedure-keywords h))
(define-values (Δkw Δkv) (filter/kw (current-caller-kw) akw kw kv))
And now the definitions are somewhat clearer:
(define (h #:c c . x)
(list c x))
(def (g ((c 0)) . args)
(list c (keyword-apply/filter h kw kv args)))
(def (f ((a 0)(b 0)) n p . ns)
(list kw kv a b n p ns (keyword-apply/filter g kw kv ns)))
You received this message because you are subscribed to the Google Groups
"Racket Users" group.
To unsubscribe from this group and stop receiving emails from it, send an email
To view this discussion on the web visit