Hi guys,
Apparently, with a desire to use keywords more in functions, I’ll have to wrap
my head around keyword-apply better. Two questions I have are:
1. Why must the kw-lst be sorted in keyword<? rather than having those
arguments appear in any order that makes sense to the caller, and then having
keyword-apply sort both kw-lst and kw-val-lst appropriately to keep the
key/value pairs synchronized?
2. The reference says:
(keyword-apply proc
kw-lst
kw-val-lst
v …
lst
#:<kw> kw-arg …)
After playing around a bit all of the following are equivalent:
(define (bar #:x x #:y y #:z z u v . w) (list x y z u v w))
(keyword-apply bar '() '() '(6 7 8 9 10) #:x 3 #:y 4 #:z 5)
(keyword-apply bar '(#:x #:y #:z) '(3 4 5) '(6 7 8 9 10))
(keyword-apply bar #:x 3 #:y 4 #:z 5 '() '() '(6 7 8 9 10))
(keyword-apply bar #:z 5 #:y 4 #:x 3 '() '() '(6 7 8 9 10))
(keyword-apply bar #:z 5 #:x 3 '(#:y) '(4) '(6 7 8 9 10))
(keyword-apply bar #:z 5 #:x 3 '(#:y) '(4) 6 7 '(8 9 10))
So it appears that ordering of keywords is only mandatory in the kw-lst. What’s
the advantage to using the kw-lst/kw-val-lst? If those lists are primarily
built using automation, rather than by hand, then question #1 is probably
explained by the idea that the automation is expected to sort the keywords
prior to the call?
-Kevin
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