Add chapter 3 part 1

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+#lang sicp
+(#%require (only racket/base print-as-expression print-mpair-curly-braces))
+(print-as-expression #f)
+(print-mpair-curly-braces #f)
+
+;; Chapter 3
+;; Modularity, Objects, and State
+
+;; 3.1
+;; Assignment and Local State
+
+(define balance 100)
+
+(#%provide withdraw)
+(define (withdraw amount)
+  (if (>= balance amount)
+    (begin
+      (set! balance (- balance amount))
+      balance)
+    "Insufficient funds"))
+
+(#%provide new-withdraw)
+(define new-withdraw
+  (let ((balance 100))
+    (lambda (amount)
+      (if (>= balance amount)
+        (begin
+          (set! balance (- balance amount))
+          balance)
+        "Insufficient funds"))))
+
+(#%provide make-withdraw)
+(define (make-withdraw balance)
+  (lambda (amount)
+    (if (>= balance amount)
+      (begin
+        (set! balance (- balance amount))
+        balance)
+      "Insufficient funds")))
+
+(#%provide make-account)
+(define (make-account balance)
+  (define (withdraw amount)
+    (if (>= balance amount)
+      (begin
+        (set! balance (- balance amount))
+        balance)
+      "Insufficient funds"))
+  (define (deposit amount)
+    (set! balance (+ balance amount))
+    balance)
+  (define (dispatch m)
+    (cond
+      ((eq? m 'withdraw) withdraw)
+      ((eq? m 'deposit) deposit)
+      (else (error "Unknown request -- MAKE-ACCOUNT" m))))
+  dispatch)
+
+#| 3.1 |#
+
+(#%provide make-accumulator)
+(define (make-accumulator sum)
+  (lambda (x)
+    (begin
+      (set! sum (+ sum x))
+      sum)))
+
+#| 3.2 |#
+
+(#%provide make-monitored)
+(define (make-monitored f)
+  (let ((call-count 0))
+    (lambda (arg)
+      (cond
+        ((and (symbol? arg) (eq? arg 'how-many-calls?))
+         call-count)
+        ((and (symbol? arg) (eq? arg 'reset-count))
+         (set! call-count 0))
+        (else
+          (set! call-count (+ call-count 1))
+          (f arg))))))
+
+#| 3.3 |#
+
+(#%provide make-account-pass)
+(define (make-account-pass balance secret-pass)
+  (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 secret-pass)
+      (cond
+        ((eq? m 'withdraw) withdraw)
+        ((eq? m 'deposit) deposit)
+        (else (error "Unknown request -- MAKE-ACCOUNT" m)))
+      (error "Incorrect password")))
+    dispatch)
+
+#| 3.4 |#
+
+(define (call-the-cops)
+  (display "WEEOOOWEEOOOWEEOOOOWEEOO")
+  (newline)
+  (display "STEP OUT OF THE VEHICLE")
+  (newline))
+
+(#%provide make-account-pass-cops)
+(define (make-account-pass-cops balance secret-pass)
+  (define fail-amount 0)
+  (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 secret-pass)
+      (begin
+        (set! fail-amount 0)
+        (cond
+          ((eq? m 'withdraw) withdraw)
+          ((eq? m 'deposit) deposit)
+          (else (error "Unknown request -- MAKE-ACCOUNT" m))))
+      (begin
+        (set! fail-amount (+ fail-amount 1))
+        (if (> fail-amount 7) (call-the-cops))
+        (error "Incorrect password"))))
+  dispatch)
+
+#| (define random-init 4) |#
+
+#| (define rand |#
+#|   (let ((x random-init)) |#
+#|     (lambda () |#
+#|       (set! x (rand-update x)) |#
+#|       x))) |#
+
+(#%provide estimate-pi)
+(define (estimate-pi trials)
+  (sqrt (/ 6 (monte-carlo trials cesaro-test))))
+
+(define (cesaro-test)
+  (= (gcd (random 10000) (random 10000)) 1))
+
+(define (monte-carlo trials experiment)
+  (define (iter trials-remaining trials-passed)
+    (cond
+      ((= trials-remaining 0)
+       (/ trials-passed trials))
+      ((experiment)
+       (iter (- trials-remaining 1) (+ trials-passed 1)))
+      (else
+       (iter (- trials-remaining 1) trials-passed))))
+  (iter trials 0))
+
+#| 3.5 |#
+
+(define (square x) (* x x))
+
+(define (random-in-range low high)
+  (let ((range (- high low)))
+    (+ low (random range))))
+
+(#%provide estimate-pi-integral)
+(define (estimate-pi-integral trials)
+  (*
+    4
+    (estimate-integral
+      (lambda (x y) (<= (+ (square x) (square y)) 1.0))
+      0 1.0
+      0 1.0
+      trials)))
+
+(define (estimate-integral P x1 x2 y1 y2 trials)
+  (*
+    (- x2 x1)
+    (- y2 y1)
+    (monte-carlo
+      trials
+      (lambda ()
+        (P
+          (random-in-range x1 x2)
+          (random-in-range y1 y2))))))
+
+#| 3.6 |#
+
+(define random-init 4)
+
+(define (rand-update x)
+  (modulo (+ (* 75 x) 74) 65537))
+
+(#%provide rand-new)
+(define rand-new
+  (let ((x random-init))
+    (lambda (sym)
+      (cond
+        ((eq? sym 'generate)
+         (set! x (rand-update x))
+         x)
+        ((eq? sym 'reset)
+         (lambda (new-value)
+           (set! x new-value)))
+        (else error "unknown symbol")))))
+
+(#%provide factorial)
+(define (factorial n)
+  (let
+    ((product 1)
+     (counter 1))
+    (define (iter)
+      (if (> counter n)
+        product
+        (begin
+          (set! product (* counter product))
+          (set! counter (+ counter 1))
+          (iter))))
+    (iter)))
+
+(#%provide factorial-bad)
+(define (factorial-bad n)
+  (let
+    ((product 1)
+     (counter 1))
+    (define (iter)
+      (if (> counter n)
+        product
+        (begin
+          (set! counter (+ counter 1))
+          (set! product (* counter product))
+          (iter))))
+    (iter)))
+
+#| 3.7 |#
+
+(#%provide make-account-pass-)
+(define (make-account-pass- balance secret-pass)
+  (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)
+    (if (eq? pass secret-pass)
+      (lambda (m)
+        (cond
+          ((eq? m 'withdraw) withdraw)
+          ((eq? m 'deposit) deposit)
+          (else (error "Unknown request -- MAKE-ACCOUNT" m))))
+      (error "Incorrect password")))
+    dispatch)
+
+(#%provide make-joint)
+(define (make-joint acc old-pass new-pass)
+  (define inner-account (acc old-pass))
+  (define (dispatch pass)
+    (lambda (m)
+      (if (eq? pass new-pass)
+        (inner-account m)
+        (error "Incorrect password"))))
+    dispatch)
+
+#| 3.8 |#
+
+(#%provide f)
+(define f
+  (let ((init false))
+    (lambda (x)
+      (if init
+        0
+        (begin (set! init true) x)))))