◊(Local Yarn Code "Diff")

    [(? string? s) s]
    [_ ""]))

;; Return the first N words out of a list of txexprs. This function will unpack the strings out of
;; the elements of one txexpr at a time until it finds the requested number of words. It aims to be
;; both reliable and fast for any size of list you pass it, and smart about the punctuation it
;; allows through.
(define (first-words txprs words-needed)
  (define punc-allowed-in-word '(#\- #\' #\% #\$ #\‘ #\’ #\# #\& #\/ #\. #\!))

(define punc-allowed-in-word '(#\- #\' #\% #\$ #\‘ #\’ #\# #\& #\/ #\. #\!))
  
  (define (word-boundary? c) (or (char-whitespace? c) (equal? c #\null) (eof-object? c)))
  (define (word-char? c) (or (char-alphabetic? c) (char-numeric? c)))
  
(define (word-boundary? c) (or (char-whitespace? c) (equal? c #\null) (eof-object? c)))
(define (word-char? c) (or (char-alphabetic? c) (char-numeric? c)))

(define (first-words txprs words-needed)
  (define in (open-input-string (->text (car txprs))))
  (define out (open-output-string))
  
  (define words-found
    (let loop ([words-found 0] [last-c #\null] [last-c-in-word? #f])
      (define c (read-char in))