Garland Word length calculator in Common Lisp

garland.lisp

;; See https://www.reddit.com/r/dailyprogrammer/comments/3d4fwj/20150713_challenge_223_easy_garland_words/
;;
;; A Garland word is one that starts and ends with the same N letters in the same order, 
;; for some N greater than 0, but less than the length of the word. 
;; Eg. onion -> 2
;;     ceramic -> 1
;;     programmer -> 0
;;     alfalfa -> 4


(defun garland (str)
  "Calculate the garland word length of a string"
  (loop with len = (length str)
     for i from 1 below len
     when (string= (subseq str 0 i) (subseq str (- len i) len))
     maximize i))

(defun garland-file (filename)
  "Get the string with a largest garland length in a file.

The file has 1 word per line"
  (with-open-file (stream filename :direction :input)
    (loop for string = (read-line stream nil :eof)
       with max-garland = 0
       with garland-string = ""
       until (eq string :eof)
       do (let ((current-garland (garland string)))
	      (when (> current-garland max-garland)
		(setf max-garland current-garland)
		(setf garland-string string)))
       finally (return (values garland-string max-garland)))))