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Author: enochii

README.md

@@ -5,9 +5,9 @@ some codes about sicp
 
 - 过程也是一等公民。过程作为参数传递爽歪歪，在ch1的cons中看到的procedure表示法还是蛮神奇的，所谓过程即数据，在丘奇计数中也高潮不断，于是技痒在ch2的用树结构表示集合也用了list和procedure两种表示法。
 
-- 抽象的魔力。当我们用不同的底层去实现一种数据结构比如树时，我们不必在意其实现细节，屏蔽作用使得如果我们改变底层实现不必去改动高层的代码（前提是你在实现高层代码时不考虑底层的细节
+- 抽象。当我们用不同的底层去实现一种数据结构比如树时，我们不必在意其实现细节，屏蔽作用使得如果我们改变底层实现不必去改动高层的代码（前提是你在实现高层代码时不考虑底层的细节
 
-- 递归的魔力。说来最近写到ch2才回过头去品味迭代过程和递归过程，虽然scheme实现迭代时一般也是递归语法，但这和我们平时说的递归（计算）不甚相同。迭代只需常量栈空间，记录的只是常数个参数。其实递归讲道理也是一种美妙的抽象，它屏蔽了下一层的实现细节，你只需要考虑当前层和下一层的关系，再弄个出口就o**k了。
+- 递归。说来最近写到ch2才回过头去品味迭代过程和递归过程，虽然scheme实现迭代时一般也是递归语法，但这和我们平时说的递归（计算）不甚相同。迭代只需常量栈空间，记录的只是常数个参数。其实递归讲道理也是一种美妙的抽象，它屏蔽了下一层的实现细节，你只需要考虑当前层和下一层的关系，再弄个出口就o**k了。
 
 - 尾递归可以优化成循环，这也可以稍稍看出递归和循环的微妙关系。
 

chapter3/sicp_3.5.4.txt

@@ -1 +1,9 @@
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chapter5/5.2/5.2.1-basic-machine.ss

@@ -46,14 +46,18 @@
       ;
       (define (dispatch message)
         (cond ((eq? message 'start)
-               ...)
+               (set-contents! pc the-instruction-sequence)
+               (excute))
               ((eq? message 'install-instruction-sequence)
                (lambda (seq)
                  (set! the-instruction-sequence seq)))
-              ((eq? message 'allocate-register) ...)
-              ((eq? message 'get-register) ...)
+              ((eq? message 'allocate-register)
+               allocate-register)
+              ((eq? message 'get-register)
+               lookup-register)
               ((eq? message 'install-operations)
-               ...)
+               (lambda (ops)
+                 (set! the-ops (append ops the-ops))))
               ((eq? message 'stack) stack)
               ((eq? message 'operations) the-ops)
               (else

justforfun/_.ss

@@ -0,0 +1,23 @@
+(define (copy lis)
+  (if (null? lis)
+      '()
+      (cons (car lis) (copy (cdr lis)))))
+;
+(define a '(1 2 3))
+(define ca (copy a))
+(set-car! ca 'xixi)
+(display ca)
+(newline)
+(display a)
+;
+;use lambda to accumulate the elements
+(define (copy-1 lis)
+  (define (iter rest recieve)
+    (if (null? rest)
+        (recieve '())
+        (iter (cdr rest)
+              (lambda (cdr_)
+                (recieve (cons (car rest) cdr_))))))
+  (iter lis
+        (lambda (cdr_)
+          cdr_)))

justforfun/__/stack.ss

@@ -0,0 +1,44 @@
+;stack
+(define (make-stack)
+  (let ((stack '()))
+    (define (empty?)
+      (null? stack))
+    (define (pop)
+      (if (null? stack)
+          (error "stack is empty! -- POP")
+          (begin ;(display (car stack))
+                 ;(display "[pop operation] ")
+                  (set! stack (cdr stack)))))
+    (define (top)
+      (if (empty?)
+          (error "stack is empty! -- TOP")
+          (car stack)))
+    (define (push x)
+      (set! stack (cons x stack)))
+    (define (dispatch message)
+      (cond ((eq? message 'pop)
+             pop)
+            ((eq? message 'push)
+             push)
+            ((eq? message 'clear)
+             clear)
+            ((eq? message 'empty?)
+             empty?)
+            ((eq? message 'top)
+             top)
+            (else (error "no such operation! -- STACK"))))
+    (define (clear)
+      (set! stack '()))
+    dispatch))
+;
+(define (pop stack)
+  ((stack 'pop)))
+(define (push x stack)
+  ((stack 'push) x))
+(define (clear stack)
+  ((stack 'clear)))
+(define (_empty? stack)
+  ((stack 'empty?)))
+(define (top stack)
+  ((stack 'top)))
+;

justforfun/__/test.ss

@@ -0,0 +1,29 @@
+(define tree-1
+  (make-tree
+   'a
+   (make-tree 'b (make-tree 'c '() '()) '())
+   (make-tree 'd
+              (make-tree 'e
+                            (make-tree 'f '() '())
+                            (make-tree 'g '() '()))
+              (make-tree 'h
+                         (make-tree 'i '() '())
+                         (make-tree 'j '() '())))))
+;
+(define test-stack #f)
+(define stack (make-stack))
+(if test-stack
+    (begin
+      ;(define stack (make-stack))
+      (push 'a stack)
+      (push 'b stack)
+      (push 'c stack)
+      (push 'd stack)
+      (pop stack)
+      (push 'e stack)
+      ;(clear stack)
+      (pop stack)
+      (pop stack)
+      (pop stack)
+      ;(pop stack)
+      (pop stack)))

justforfun/__/tree.ss

@@ -0,0 +1,43 @@
+;(root left-child right-child)
+;interfaces
+(define (root tree) (car tree))
+(define (left tree) (cadr tree))
+(define (right tree) (caddr tree))
+;
+(define (preorder tree)
+  (if (null? tree)
+      'done
+      (begin
+        (display (root tree))(display " ")
+        (preorder (left tree))
+        (preorder (right tree))
+        )))
+(define (inorder tree)
+  (if (null? tree)
+      'done
+      (begin
+        (inorder (left tree))
+        (display (root tree))(display " ")
+        (inorder (right tree))
+        )))
+(define (postorder tree)
+  (if (null? tree)
+      'done
+      (begin
+        (postorder (left tree))
+        (postorder (right tree))
+        (display (root tree))(display " ")
+        )))
+;
+(define (make-tree a b c)
+  (list a b c))
+;
+(display "visit by recursion\n")
+(load ".//test.ss")
+(display "preorder\n")
+(preorder tree-1)(newline)
+(display "inorder\n")
+(inorder tree-1)(newline)
+(display "postorder\n")
+(postorder tree-1)(newline)
+(display "--------seperator--------\n")