Bloodwolf
- 浏览: 88774 次
- 性别:
- 来自: 北京
-
最新评论
-
Bloodwolf：
gaowei52306 写道怎样在Linux中设置路由，用此方 ...
Loadrunner IP欺骗 -
gaowei52306：
怎样在Linux中设置路由，用此方法在Windows操作系统上 ...
Loadrunner IP欺骗
文章列表
Exercise 2.40. Define a procedure unique-pairs that, given an integer n, generates the sequence of pairs (i,j) with 1< j< i< n. Useunique-pairs to simplify the definition of prime-sum-pairs given above.
(define (unique-pairs n)
(accumulate append
'()
...
Exercise 2.39. Complete the following definitions of reverse (exercise 2.18) in terms of fold-right and fold-left from exercise 2.38:
(define (reverse sequence) (fold-right (lambda (x y) <??>) nil sequence))(define (reverse sequence) (fold-left (lambda (x y) <??>) nil sequence) ...
Exercise 2.38. The accumulate procedure is also known as fold-right, because it combines the first element of the sequence with the result of combining all the elements to the right. There is also a fold-left, which is similar to fold-right, except that it combines elements working in the opposit ...
Exercise 2.37. Suppose we represent vectors v = (vi) as sequences of numbers, and matrices m = (mij) as sequences of vectors (the rows of the matrix). For example, the matrix
is represented as the sequence ((1 2 3 4) (4 5 6 6) (6 7 8 9)). With this representation, we can use sequence operat ...
Exercise 2.36. The procedure accumulate-n is similar to accumulate except that it takes as its third argument a sequence of sequences, which are all assumed to have the same number of elements. It applies the designated accumulation procedure to combine all the first elements of the sequences, al ...
Exercise 2.35. Redefine count-leaves from section 2.2.2 as an accumulation:
(define (count-leaves t) (accumulate <??> <??> (map <??> <??>)))
(define (accumulate op initial sequence)
(if (null? sequence)
initial
(op (car sequence)
...
Exercise 2.34. Evaluating a polynomial in x at a given value of x can be formulated as an accumulation. We evaluate the polynomial
using a well-known algorithm called Horner's rule, which structures the computation as
In other words, we start with an, multiply by x, add an-1, multiply ...
Exercise 2.33. Fill in the missing expressions to complete the following definitions of some basic list-manipulation operations as accumulations:
(define (map p sequence) (accumulate (lambda (x y) <??>) nil sequence))(define (append seq1 seq2) (accumulate cons <??> <??>))( ...
Exercise 2.32. We can represent a set as a list of distinct elements, and we can represent the set of all subsets of the set as a list of lists. For example, if the set is (1 2 3), then the set of all subsets is (() (3) (2) (2 3) (1) (1 3) (1 2) (1 2 3)). Complete the following definition of a pr ...
Exercise 2.31. Abstract your answer to exercise 2.30 to produce a procedure tree-map with the property that square-tree could be defined as
(define (square-tree tree) (tree-map square tree))
(define (tree-map operation tree)
(map (lambda (sub-tree)
(if (pair? sub-tree ...
Exercise 2.30. Define a procedure square-tree analogous to the square-list procedure of exercise 2.21. That is, square-list should behave as follows:
(square-tree (list 1 (list 2 (list 3 4) 5) (list 6 7)))(1 (4 (9 16) 25) (36 49))
Define square-tree both directly (i.e., wit ...
Exercise 2.29. A binary mobile consists of two branches, a left branch and a right branch. Each branch is a rod of a certain length, from which hangs either a weight or another binary mobile. We can represent a binary mobile using compound data by constructing it from two branches (for example, u ...
Exercise 2.28. Write a procedure fringe that takes as argument a tree (represented as a list) and returns a list whose elements are all the leaves of the tree arranged in left-to-right order. For example,
(define x (list (list 1 2) (list 3 4)))(fringe x)(1 2 3 4)(fringe (list x x))(1 2 3 4 ...
Exercise 2.27. Modify your reverse procedure of exercise 2.18 to produce a deep-reverse procedure that takes a list as argument and returns as its value the list with its elements reversed and with all sublists deep-reversed as well. For example,
(define x (list (list 1 2) (list 3 4)))x((1 2) ...
Exercise 2.26. Suppose we define x and y to be two lists:
(define x (list 1 2 3))(define y (list 4 5 6))
What result is printed by the interpreter in response to evaluating each of the following expressions:
(append x y)(cons x y)(list x y)
求值结果分别是：
(append x y)->(1 2 ...