In Python, we can extract known keywords easily:
def f(a, *args, b=2, c=3, **kwargs):
return (a, args, b, c, kwargs)
print(f(42, 43, c=44, d=45)) #=> (42, (43,), 2, 44, {'d': 45})
Doing so in Racket is not as easy.
#lang racket/base
(provide lambda/kw define/kw)
(require racket/list
(for-syntax racket/base))
(define-syntax-rule (lambda/kw (kws kw-args . rst) body ...)
(let ([f (λ (kws kw-args . rst) body ...)])
(define-values (ignored used-kws) (procedure-keywords f))
(make-keyword-procedure
(λ (actual/kws actual/kw-args . actual/rest)
(define-values (used-kws+kw-args left-kws+kw-args)
(partition (λ (e) (member (car e) used-kws))
(map cons actual/kws actual/kw-args)))
(keyword-apply f
(map car used-kws+kw-args)
(map cdr used-kws+kw-args)
(list* (map car left-kws+kw-args)
(map cdr left-kws+kw-args)
actual/rest))))))
(define-syntax-rule (define/kw (f . rst) body ...)
(define f (lambda/kw rst body ...)))
(module+ test
(require rackunit)
(define/kw (f kws kw-args #:b b #:c [c 16] #:d [d 32] a . rst)
(list kws kw-args a b c d rst))
(check-equal? (f 1 2 #:b 4 #:c 8 #:e 64) '((#:e) (64) 1 4 8 32 (2))))
While I am happy with the above macro, I wonder if this could be a part of
`make-keyword-procedure`, so that we can simply use:
(define g (make-keyword-procedure
(λ (kws kw-args #:b b #:c [c 16] #:d [d 32] a . rst)
(list kws kw-args a b c d rst))))
(check-equal? (g 1 2 #:b 4 #:c 8 #:e 64) '((#:e) (64) 1 4 8 32 (2)))
--
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 racket-users+unsubscr...@googlegroups.com.
For more options, visit https://groups.google.com/d/optout.
