スキームにput＆getプロシージャを実装する方法は？

Question

私はsicp本を読んでいます。私はセクション2.4.3、Data-Directed Programming and Additivityについています。

としては、テキストに言及し、の実装はとが手順は、第3章（3.3.3）に記載されている取得置きます。しかし、私はこれらの手順を見つけることができませんでした、多分プロシージャの名前はそこに異なるでしょう。

だから私は、下記のようにREPLがエラーを投げ、本の中で与えられたコード（例）を実行しようとしたとき：ここ

1 ]=> (make-from-mag-ang 4 5) 

;Unbound variable: get 
;To continue, call RESTART with an option number: 
; (RESTART 3) => Specify a value to use instead of get. 
; (RESTART 2) => Define get to a given value. 
; (RESTART 1) => Return to read-eval-print level 1. 

はコードです：

(define (attach-tag type-tag contents) 
    (cons type-tag contents)) 

(define (type-tag datum) 
    (if (pair? datum) 
    (car datum) 
    (error "Bad tagged datum -- TYPE-TAG" datum))) 

(define (contents datum) 
    (if (pair? datum) 
    (cdr datum) 
    (error "Bad tagged datum -- CONTENTS" datum))) 

(define (rectangular? z) 
    (eq? (type-tag z) 'rectangular)) 

(define (polar? z) 
    (eq? (type-tag z) 'polar)) 


(define (install-rectangular-package) 
    ;; internal procedure 
    (define (real-part z) (car z)) 
    (define (imag-part z) (cdr z)) 
    (define (magnitude z) 
    (sqrt (+ (square (real-part z)) (square (imag-part z))))) 
    (define (angle z) 
    (atan (imag-part z) (real-part z))) 
    (define (make-from-real-imag x y) (cons x y)) 
    (define (make-from-mag-ang r a) 
    (cons (* r (cos a)) (* r (sin a)))) 

    ;; interface to the rest of the system 
    (define (tag x) (attach-tag 'rectangular x)) 
    (put 'real-part '(rectangular) real-part) 
    (put 'imag-part '(rectangular) imag-part) 
    (put 'magnitude '(rectangular) magnitude) 
    (put 'angle '(rectangular) angle) 
    (put 'make-from-real-imag '(rectangular) (lambda (x y) (tag (make-from-real-imag x y)))) 
    (put 'make-from-mag-ang '(rectangular) (lambda (r a) (tag (make-from-mag-ang r a)))) 
    'done) 


(define (install-polar-package) 
    ;; internal procedure 
    (define (real-part z) (* (magnitude z) (cos (angle z)))) 
    (define (imag-part z) (* (magnitude z) (sin (angle z)))) 
    (define (magnitude z) (car z)) 
    (define (angle z) (cdr z)) 
    (define (make-from-real-imag x y) 
    (cons (sqrt (+ (square x) (square y))) (atan y x))) 
    (define (make-from-mag-ang r a) (cons r a)) 

    ;; interface to the rest of the system 
    (define (tag x) (attach-tag 'polar x)) 
    (put 'real-part '(polar) real-part) 
    (put 'imag-part '(polar) imag-part) 
    (put 'magnitude '(polar) magnitude) 
    (put 'angle '(polar) angle) 
    (put 'make-from-real-imag '(polar) (lambda (x y) (tag (make-from-real-imag x y)))) 
    (put 'make-from-mag-ang '(polar) (lambda (r a) (tag (make-from-mag-ang r a)))) 
    'done) 


(define (apply-generic op . args) 
    (let ((type-tags (map type-tag args))) 
    (let ((proc (get op type-tags))) 
     (if proc 
     (apply poc (map contents args)) 
     (error "No method for these types -- APPLY-GENERIC" (list op type-tags)))))) 

(define (real-part z) (apply-generic 'real-part z)) 

(define (imag-part z) (apply-generic 'imag-part z)) 

(define (magnitude z) (apply-generic 'magnitude z)) 

(define (angle z) (apply-generic 'angle z)) 

(define (make-from-real-imag x y) 
    ((get 'make-from-real-imag 'rectangular) x y)) 

(define (make-from-mag-ang r a) 
    ((get 'make-from-mag-ang 'polar) r a)) 

誰でも伝えることができます私は本の中で前進することができるように、これらの手順の実際の実装？どんな助けもありがとう。おかげ

Answer 1

は

https://mitpress.mit.edu/sicp/full-text/sicp/book/node63.html

(define (make-table) 
    (let ((local-table (list '*table*))) 
    (define (lookup key-1 key-2) 
     (let ((subtable (assoc key-1 (cdr local-table)))) 
     (if subtable 
      (let ((record (assoc key-2 (cdr subtable)))) 
       (if record 
        (cdr record) 
        false)) 
      false))) 
    (define (insert! key-1 key-2 value) 
     (let ((subtable (assoc key-1 (cdr local-table)))) 
     (if subtable 
      (let ((record (assoc key-2 (cdr subtable)))) 
       (if record 
        (set-cdr! record value) 
        (set-cdr! subtable 
          (cons (cons key-2 value) 
            (cdr subtable))))) 
      (set-cdr! local-table 
         (cons (list key-1 
            (cons key-2 value)) 
          (cdr local-table))))) 
     'ok)  
    (define (dispatch m) 
     (cond ((eq? m 'lookup-proc) lookup) 
      ((eq? m 'insert-proc!) insert!) 
      (else (error "Unknown operation - TABLE" m)))) 
    dispatch)) 

(define operation-table (make-table)) 
(define get (operation-table 'lookup-proc)) 
(define put (operation-table 'insert-proc!))