Exercise3.1～3.49

3 Modularity, Objects, and State

3.1 Assignment and Local State

3.1.1 Local State Variables

Exercise 3.1

(define (make-accumulator augend)
  (lambda (addend)
    (begin
      (set! augend (+ augend addend))
      augend)))

by iwk

Exercise 3.2

(define (make-monitored f)
  (let ((count 0))
    (define (how-many-calls?)
      count)
    (define (reset-count)
      (set! count 0)
      count)
    (define (counting-procedure x)
      (set! count (+ count 1))
      (f x))
    (define (dispatch m)
      (cond ((eq? m 'how-many-calls?) (how-many-calls?))
	    ((eq? m 'reset-count) (reset-count))
	    (else (counting-procedure m))))
    dispatch))

by iwk

Exercise 3.3

(define (make-account balance passwd)
  (define (withdraw amount)
    (if (>= balance amount)
	(begin
	  (set! balance (- balance amount))
	  balance)
	"Insufficient funds"))
  (define (deposit amount)
    (set! balance (+ balance amount))
    balance)
  (define (dispatch pass m)
    (if (eq? pass passwd)
	(cond ((eq? m 'withdraw) withdraw)
	      ((eq? m 'deposit) deposit)
	      (else (error "Unknown request -- MAKE-ACCOUNT"
			   m)))
	(error "Incorrect password" pass)))
  dispatch)

by iwk

Exercise 3.4

3.1.2 The Benefits of Introducing Assignment

Exercise 3.5

Exercise 3.6

3.1.3 The Costs of Introducing Assignment

Exercise 3.7

Exercise 3.8

3.2 The Environment Model of Evaluation

3.2.1 The Rules for Evaluation

3.2.2 Applying Simple Procedures

Exercise 3.9

3.2.3 Frames as the Repository of Local State

Exercise 3.10

3.2.4 Internal Definitions

Exercise 3.11

3.3 Modeling with Mutable Data

3.3.1 Mutable List Structure

Exercise 3.12

Exercise 3.13

Exercise 3.14

Exercise 3.15

Exercise 3.16

Exercise 3.17

Exercise 3.18

Exercise 3.19

Exercise 3.20

3.3.2 Representing Queues

Exercise 3.21

Exercise 3.22

Exercise 3.23

3.3.3 Representing Tables

Exercise 3.24

Exercise 3.25

Exercise 3.26

Exercise 3.27

3.3.4 A Simulator for Digital Circuits

Exercise 3.28

Exercise 3.29

Exercise 3.30

Exercise 3.31

Exercise 3.32

3.3.5 Propagation of Constraints

Exercise 3.33

Exercise 3.34

Exercise 3.35

Exercise 3.36

Exercise 3.37

3.4 Concurrency: Time Is of the Essence

3.4.1 The Nature of Time in Concurrent Systems

Exercise 3.38

3.4.2 Mechanisms for Controlling Concurrency

Exercise 3.39

Exercise 3.40

Exercise 3.41

Exercise 3.42

Exercise 3.43

Exercise 3.44

Exercise 3.45

Exercise 3.46

Exercise 3.47

Exercise 3.48

Exercise 3.49