;;; Examples of tallying.  Fun fun fun.

(define tally
  (lambda (pred? lst)
    (cond
      ((null? lst) 0)
      ((pred? (car lst)) (+ 1 (tally pred? (cdr lst))))
      (else (tally pred? (cdr lst))))))

(define make-tallier
  (lambda (pred?) ; The parameter to make-tallier
    ; Return a new procedure of one parameter, lst
    (lambda (lst)
      (tally pred? lst))))

(define count
  (lambda (pred?)
    (letrec ((counter
              (lambda (lst)
                (cond
                  ((null? lst) 0)
                  ((pred? (car lst)) (+ 1 (counter (cdr lst))))
                  (else (counter (cdr lst)))))))
      counter)))