Add exercise3-1 to 3-4.

Author: ramsayleung

README.org

@@ -21,3 +21,13 @@
   #+begin_src shell
     raco pkg install --auto --batch # 类似 JavaScript 的 npm install
   #+end_src
+* 运行
+  运行所有的习题
+  #+begin_src shell
+    raco test -t .
+  #+end_src
+
+  运行指定的习题:
+  #+begin_src shell
+    raco test chapter1/exercise1-10.scm 
+  #+end_src

chapter3/exercise3-1.rkt

@@ -0,0 +1,20 @@
+#lang racket
+(define (make-accumulator total)
+  (lambda (next)
+    (begin (set! total (+ total next))
+           total)))
+
+(module+ test
+  (require rackunit)
+  (require rackunit/text-ui)
+
+  (define acc (make-accumulator 5))
+  (define module-test
+    (test-suite
+     "Tests for make-accumulator"
+     (check-equal? (acc 5) 10)
+     (check-equal? (acc 10) 20)
+     (check-equal? (acc -30) -10)
+     ))
+
+  (run-tests module-test))

chapter3/exercise3-2.rkt

@@ -0,0 +1,27 @@
+#lang racket
+
+(define (make-monitored func)
+  (let ((count 0))
+    (lambda (input)
+      (cond ((eq? input 'how-many-calls?) count)
+            ((eq? input 'reset-count) (set! count 0) 'reset)
+            (else
+             (set! count (+ count 1))
+             (func input))))))
+
+(module+ test
+  (require rackunit)
+  (require rackunit/text-ui)
+
+  (define s (make-monitored sqrt))
+  (define module-test
+    (test-suite
+     "Tests for make-monitored"
+     (check-equal? (s 100) 10)
+     (check-equal? (s 100) 10)
+     (check-equal? (s 'how-many-calls?) 2)
+     (s 'reset-count)
+     (check-equal? (s 'how-many-calls?) 0)
+     ))
+
+  (run-tests module-test))

chapter3/exercise3-3.rkt

@@ -0,0 +1,37 @@
+#lang racket
+(define (make-account balance password)
+  (define (withdraw amount)
+    (if (>= balance amount)
+        (begin (set! balance (- balance amount))
+               balance)
+        "Insufficient funds"))
+
+  (define (deposit amount)
+    (set! balance (+ balance amount))
+    balance)
+
+  (define (dispatch pwd m)
+    (if (eq? pwd password)
+        (cond ((eq? m 'withdraw) withdraw)
+              ((eq? m 'deposit) deposit)
+              (else (error "Unknown request --MAKE_ACCOUNT" m)))
+        (error "Incorrect password")
+        ))
+  dispatch)
+
+(module+ test
+  (require rackunit)
+  (require rackunit/text-ui)
+  (define acc (make-account 100 'secret-password))
+
+  (define module-test
+    (test-suite
+     "Tests for make-account with password"
+     (check-equal? ((acc 'secret-password 'withdraw) 40) 60)
+     (check-equal? ((acc 'secret-password 'withdraw) 40) 20)
+     ;; Test that an exception is thrown with the correct message
+     (check-exn exn:fail? (lambda () ((acc 'invalid-password 'deposit) 40)))
+     (check-exn (regexp "Incorrect password") (lambda () ((acc 'invalid-password 'deposit) 40)))
+     ))
+
+  (run-tests module-test))

chapter3/exercise3-4.rkt

@@ -0,0 +1,74 @@
+#lang racket
+(define (make-account balance password)
+  (let ((failed-count 0))
+    (define (withdraw amount)
+      (if (>= balance amount)
+          (begin (set! balance (- balance amount))
+                 balance)
+          "Insufficient funds"))
+
+    (define (deposit amount)
+      (set! balance (+ balance amount))
+      balance)
+
+    (define (call-the-cops)
+      (error "Calling 911"))
+
+    (define (dispatch pwd m)
+      (if (eq? pwd password)
+          ;; reset the failed count once the password is correct
+          (begin (set! failed-count 0)
+                 (cond ((eq? m 'withdraw) withdraw)
+                       ((eq? m 'deposit) deposit)
+                       (else (error "Unknown request --MAKE_ACCOUNT" m))))
+          (begin (set! failed-count (+ failed-count 1))
+                 (if (> failed-count 7)
+                     (call-the-cops)
+                     (error "Incorrect password")))
+          ))
+    dispatch))
+
+(module+ test
+  (require rackunit)
+  (require rackunit/text-ui)
+  (define acc (make-account 100 'secret-password))
+  (define acc2 (make-account 100 'secret-password))
+  (define acc3 (make-account 100 'secret-password))
+
+  (define module-test
+    (test-suite
+     "Tests for make-account with password and limited attempt"
+     (check-equal? ((acc 'secret-password 'withdraw) 40) 60)
+     (check-equal? ((acc 'secret-password 'withdraw) 40) 20)
+     ;; Test that an exception is thrown with the correct message
+     (check-exn exn:fail? (lambda () ((acc 'invalid-password 'deposit) 40)))
+     (check-exn (regexp "Incorrect password") (lambda () ((acc 'invalid-password 'deposit) 40)))
+
+     "Tests for make-account, 7 consecutive attmepts failed, call cops eventually"
+     (check-exn (regexp "Incorrect password") (lambda () ((acc2 'invalid-password 'deposit) 40)))
+     (check-exn (regexp "Incorrect password") (lambda () ((acc2 'invalid-password 'deposit) 40)))
+     (check-exn (regexp "Incorrect password") (lambda () ((acc2 'invalid-password 'deposit) 40)))
+     (check-exn (regexp "Incorrect password") (lambda () ((acc2 'invalid-password 'deposit) 40)))
+     (check-exn (regexp "Incorrect password") (lambda () ((acc2 'invalid-password 'deposit) 40)))
+     (check-exn (regexp "Incorrect password") (lambda () ((acc2 'invalid-password 'deposit) 40)))
+     (check-exn (regexp "Incorrect password") (lambda () ((acc2 'invalid-password 'deposit) 40)))
+     (check-exn (regexp "Calling 911") (lambda () ((acc2 'invalid-password 'deposit) 40)))
+
+     "Tests for make-account, 1 attempt succeeded, but subsequence attempt failed, call cops eventually"
+     (check-exn (regexp "Incorrect password") (lambda () ((acc3 'invalid-password 'deposit) 40)))
+     (check-exn (regexp "Incorrect password") (lambda () ((acc3 'invalid-password 'deposit) 40)))
+     ;; successful attempt reset the failed count
+     (check-equal? ((acc3 'secret-password 'withdraw) 40) 60)
+     (check-exn (regexp "Incorrect password") (lambda () ((acc3 'invalid-password 'deposit) 40)))
+     (check-exn (regexp "Incorrect password") (lambda () ((acc3 'invalid-password 'deposit) 40)))
+     (check-exn (regexp "Incorrect password") (lambda () ((acc3 'invalid-password 'deposit) 40)))
+     (check-exn (regexp "Incorrect password") (lambda () ((acc3 'invalid-password 'deposit) 40)))
+     (check-exn (regexp "Incorrect password") (lambda () ((acc3 'invalid-password 'deposit) 40)))
+     (check-exn (regexp "Incorrect password") (lambda () ((acc3 'invalid-password 'deposit) 40)))
+     (check-exn (regexp "Incorrect password") (lambda () ((acc3 'invalid-password 'deposit) 40)))
+     ;; call-the-cops after consecutive 7 failed attempts
+     (check-exn (regexp "Calling 911") (lambda () ((acc3 'invalid-password 'deposit) 40)))
+     )
+    )
+
+  (run-tests module-test))