keyword-apply-dict.rkt

#lang racket

;; proc : procedure? ; procedure to apply
;; dict : dict? ; dictionary of keywords and values
;;     A key can be either a keyword or a symbol that is turned into a keyword.
;; largs : list? ; positional arguments
;; Returns the result of the application of proc to the positional arguments and the keyword values.
(define (keyword-apply/dict proc dict largs)
  (define alist
    (sort
     (for/list ([(k v) (in-dict dict)])
       (cons
        (cond [(keyword? k) k]
              [(symbol? k) (string->keyword (symbol->string k))]
              [else (error "Not a keyword or symbol:" k)])
        v))
     keyword<? #:key car))
  (keyword-apply proc (map car alist) (map cdr alist) largs))

(define (f a b #:c c #:d d)
  (list a b c d))

(keyword-apply/dict f '((c . 3) (#:d . 4)) '(1 2)) ; -> '(1 2 3 4)