(define (let->combination exp)
  (if  (named-let? exp)
       (let ((proc-name (let-named-var exp))
             (proc-body (let-named-body exp))
             (formal-params (let-named-formal-params exp))
             (real-params (let-named-real-params exp)))
         (sequence->exp
          (list (list 'define proc-name
                      (make-lambda formal-params proc-body))
                (list proc-name
                      real-params))))
       (let ((formal-params (map car (let-vars exp)))
             (real-params (map cdr (let-vars exp)))
             (lambda-body (let-body exp)))
         (list (make-lambda formal-params lambda-body)
               real-params))
           

(define (let-named-var exp)
  (cadr exp))

(define (let-named-formal-params exp)
  (map car (caddr exp)))

(define (let-named-real-params exp)
  (map cdr (caddr exp)))

(define (named-let? exp)
  (and (let? exp)
       (symbol? (cadr exp))))