Stop show with sound -- Keyboard shortcut: 'x'  Next slide in show -- Keyboard shortcut: 'n'  2 minutes, 52 secondsName binding, Recursion, Iteration, and Continuations - slide 23 : 42

Examples with recursion: string-of-char-list?
The function string-of-char-list? is a predicate (a boolean function) that finds out if a string is formed exclusively by characters from a particular alphabet.
(define (string-of-char-list? str char-list)
  (string-of-char-list-1? str char-list 0 (string-length str)))

(define (string-of-char-list-1? str char-list i lgt)
  (if (= i lgt)
      (and (memv (string-ref str i) char-list)
           (string-of-char-list-1? str char-list (+ i 1) lgt))))
Applications of string-of-char-list?.