demo map

dictionary.rkt

#lang racket

(provide
 (all-defined-out))


; new table
(define empty-table
  (lambda (name)
    '()))


(define all-keys
  (lambda (origin-table)
    (letrec [(search-all-keys
              (lambda (name value table)
                (println name)
                (table search-all-keys)))]
      (origin-table search-all-keys))))


; extend :: name -> value -> table -> table
(define extend
  (lambda (name value table)
    (lambda (search)
      (search name value table))))


; multi-extend :: [name] -> [value] -> table -> table
(define multi-extend
  (lambda (names values table)
    (if (null? names)
       table
       (extend (car names) (box (car values))
              (multi-extend (cdr names) (cdr values) table)))))


; lookup :: key -> table -> Maybe value
(define lookup
  (lambda (name table)
    (letrec [(search-by-name
              (lambda (name2)
                (lambda (name1 value table)
                  (cond
                    [(eq? name2 name1) value]
                    [else (table (search-by-name name2))]))))]
      (table (search-by-name name)))))


; debug-table :: table -> Nothing
(define debug-table
  (lambda (table)
    (letrec [( show-all
               (lambda (name value table)
                 (print name)
                 (print ":")
                 (println value)
                 (table show-all)))]
      (table show-all))))