SICP_3.25

(define false #f)
(define true #t)

(define (make-table)
  (let ((local-table (list '*table*)))

     (define (assoc key records)
      (cond ((null? records) false)
            ((equal? (caar records) key) (car records))
            (else (assoc key (cdr records)))))

    (define (lookup keys)
      (define (lookup-helper keys table)
        (let ((subtable (assoc (car keys) (cdr table))))
          (if subtable
              (if (null? (cdr keys))
                  (cdr subtable)
                  (lookup-helper (cdr keys) subtable))
              false)))
      (lookup-helper keys local-table))

    (define (insert! keys value)
      (define (insert-helper! keys table)
        (if (null? table)
            (if (null? (cdr keys))
                (cons (car keys) value)
                (list (car keys) (insert-helper! (cdr keys) '())))
            (let ((sub (assoc (car keys) (cdr table))))
              (if sub
                  (if (null? (cdr keys))
                      (set-cdr! sub value)
                      (insert-helper! (cdr keys) sub))
                  (if (null? (cdr keys))
                      (set-cdr! table (cons (cons (car keys) value) (cdr table)))
                      (set-cdr! table (cons
                                       (list (car keys)(insert-helper! (cdr keys) '()))
                                       (cdr table))))))))
      (insert-helper! keys local-table)
      'ok)
  
    (define (dispatch m)
      (cond ((eq? m 'lookup-proc) lookup)
            ((eq? m 'insert-proc) insert!)
            (else (error "Unknow operation --TABLE" m))))

    dispatch))

(define t1 (make-table))

((t1 'insert-proc) '(key1 key2 key4) 5)

((t1 'lookup-proc) '(key1 key2 key4))