(define longest-list-in-list
  (lambda (los)
    (let ((longer-list
           (lambda (left right)
             (if (<= (length right) (length left))
                 left
                 right)))
          (sam (display "Sam")))  ; Hack to see how many times let is executed.
      ; If there is only one list, that list must be the longest.
      (if (null? (cdr los))
          (car los)
          ; Otherwise, take the longer of the first list and the
          ; longest remaining list.
          (longer-list (car los) (longest-list-in-list (cdr los)))))))

(define longest-list-in-list2
  (let ((longer-list
         (lambda (left right)
           (if (<= (length right) (length left))
               left
               right)))
        (sam (display "Samuel"))) ; Hack to see how many times let is executed.
    (lambda (los)
      ; If there is only one list, that list must be the longest.
      (if (null? (cdr los))
          (car los)
          ; Otherwise, take the longer of the first list and the
          ; longest remaining list.
          (longer-list (car los) (longest-list-in-list2 (cdr los)))))))

; Format of a let
;   (let ((name exp))
;     body)
(define largest-in-list
  (lambda (los)
    (letrec ((kernel 
              (lambda (los)
                ; If there is only one list, that list must be the longest.
                (if (null? (cdr los))
                    (car los)
                    ; Otherwise, take the longer of the first list and the
                    ; longest remaining list.
                    (max (car los) (kernel (cdr los)))))))
      (if (not (list? los))
          (error 'largest-in-list "Expects a list")
          (kernel los)))))

(define largest-in-list
  (lambda (los)
    (let kernel ; The name of a procedure
      ((stuff los)) ; Param initial value
      (if (null? (cdr stuff))
          (car stuff)
          (max (car stuff) (kernel (cdr stuff)))))))