palindrome-test.lisp

; palindrome-test.lisp is a (Common) LISP program by Chris Clarke
; version: removes spaces and punctuation from input string (30.07.2018)

(defun ispalindrome (txt)
   (setq txt1 (string-downcase txt)) ; convert to lower case
   ; punctuation set
   (setq punct '(vector #\SPACE #\COMMA #\. #\! #\- #\: #\; #\" #\' #\( #\) ))
   (loop for ch in punct
      do (setq txt1 (remove ch txt1)) ; remove punctuation characters from txt1
   )
   (return-from ispalindrome (string= txt1 (reverse txt1)))
)

(terpri)
(princ "Enter text: ")
(setq txt (read-line))
(terpri)
(princ #\")
(princ txt)
(princ #\")
(if (ispalindrome txt)
   (princ " is a palindrome.")
   (princ " is not a palindrome!")
)