[racket] Apply proc with hasheq

The function I provided for hash->keyword-apply is unfortunately
broken; I forgot that there's a requirement on the order of the
keywords we pass to it.  Here's a revised version:


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(define (hash->keyword-apply f a-hash [rest-args '()])
  (define-values (keys vals)
    (for/fold ([keys '()] [vals '()])
              ([k (sort (hash-keys a-hash) string>? #:key symbol->string)])
      (values (cons (string->keyword (symbol->string k)) keys)
              (cons (hash-ref a-hash k) vals))))
  (keyword-apply f keys vals rest-args))
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