Keyword arguments

[Lalo Martins <lalo at hackandroll dot org>]

I suggest this is added to the FAQ somewhere:

Q:

How do I create a procedure that takes keyword arguments? Such
that both calls are legal (and work):

(my-proc "test" #:foo 1 #:bar 2)
(my-proc "test" #:bar 0)

A:

guile> (use-modules (ice-9 optargs))
guile> (define my-proc (lambda* (req #&key foo bar)
...   (display "req = ") (display req) (newline)
...   (if (bound? foo) (begin (display "foo = ") (display foo)
(newline)))
...   (if (bound? bar) (begin (display "bar = ") (display bar)
(newline)))
... )
... )
guile> (my-proc 1)
1
guile> (my-proc 1 2)
1
guile> (my-proc 1 #:foo 2)
1
foo = 2
guile> (my-proc 1 #:bar 2)
1
bar = 2
guile> (my-proc 1 #:bar 2 #:foo 3)
1
foo = 3
bar = 2
guile> (my-proc 1 #:bar 2 #:foo 3 #:bar 0)
1
foo = 3
bar = 0



Still, I think it would be useful if I could freely intermix
keyword and non-keyword arguments in the call, like
  (my-proc #:foo 1 #:bar 2 "test")
I can use a "rest" parameter, but optargs will fill it with the
keywords too, which is not good. For CDH I'm using the ugly
workaround of using the last element from "rest" and ignoring
anything else...

[]s,
                                               |alo
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