Improved implementation of space intercalation for chatbot

ae.scm

(use-modules (srfi srfi-1))

(define (ae string)
  (if (string-null? string)
      string
      (let loop ((result (make-string (1- (* 2 (string-length string)))))
		 (index 0)
		 (len (string-length string))
		 (blank-line #t))
	(if (= index len)
	    (if blank-line
		(make-string 0)
		result)
	    (let ((char (string-ref string index)))
	      (string-set! result (* 2 index) char)
	      (when (< index (1- len))
		(string-set! result (1+ (* 2 index)) #\space))
	      (loop result (1+ index) len (not (or (not blank-line)
						   (not (char-whitespace? char))))))))))