(define call-arity-1
  (lambda params
    (display params)
    (newline)
    (if (null? params)
        0
        (+ 1 (call-arity-1 (cdr params))))))

(define call-arity-2
  (lambda params
    (let kernel ((remaining params))
      (if (null? remaining)
          0
          (+ 1 (kernel (cdr remaining)))))))

(define call-arity-3
  (letrec ((kernel (lambda (remaining)
                     (if (null? remaining)
                         0
                         (+ 1 (kernel (cdr remaining)))))))
    (lambda params
      (kernel params))))

(define call-arity-4
  (lambda params
    (length params)))