Gambit's current Github source builds and installs a number of demos for
SRFI 231, which, after installation, can be run as

heine:~/programs/gambit/gambit> gsi srfi/231/demo
((palindrome? "") => #t)
((palindrome? "A") => #t)
((palindrome? "AA") => #t)
((palindrome? "AB") => #f)
((palindrome? "ABA") => #t)
((palindrome? "ABBA") => #t)
((palindrome? "ABCA") => #f)
((palindrome? "AManAPlanACanalPanama") => #t)

Demo source code:

(import (srfi 231))

(define (palindrome? s) ;;; is the string s a palindrome, ignoring case
   (let* ((n
           (string-length s))
          (a    ;; an array accessing the characters of s
           (make-array (make-interval (vector n))
                       (lambda (i) (string-ref s i))))
          (ra   ;; the characters accessed in reverse order
           (array-reverse a))
          (half-domain
           (make-interval (vector (quotient n 2)))))
     ;; when n is 0 or 1 the following extracted arrays are empty
     (array-every char-ci=?
                  (array-extract a half-domain)    ;; first half of s
                  (array-extract ra half-domain))));; reversed second
half of s

(for-each (lambda (s) (pretty-print `((palindrome? ,s) => ,(palindrome?
s))))
           '("" "A" "AA" "AB" "ABA" "ABBA" "ABCA" "AManAPlanACanalPanama"))

(print "\nDemo source code:\n\n" (read-file-string (this-source-file)))

;; Other demos: demo2 -- Conway's Game of Life.
;;              demo3 -- Matrix operations, Gaussian elimination
;;              demo4 -- Image processing, wavelet transform, denoising.

Similarly for srfi/231/demo2, etc.

Brad