scheme

问题 Here's my data definition, (define-struct leaf ()) ;; interpretation: represents a leaf on a BT, a node with no children (define-struct node (word left right)) ;; interpretation: represents a node on a BT with a word, a left and a right ;; subtree ;; A BinaryTree (BT) is one of ;; - (make-leaf) ;; - (make-node String BT BT) ;; bt-has? : BT String -> Boolean ;; given a BT tree and a String w and returns true if w is in the tree ;; and false otherwise (define (bt-has? tree w) (cond [(leaf? tree

问题 c++ int loop(int x, int y, int z) { int result = 0; for ( int i = x; i < y; i+=z ) { result += i; } return result; } Just i try that by scheme (letrec ((my-loop (lambda (a b c) (begin (let ((i a) (s 0)) (if (< i b) (set! s (+ s i)) s))))))(my-loop (+ a c) b c)) please write correct code of scheme.... 回答1: Here's a straightforward translation to a do loop: (define (foo x y z) (do ((result 0 (+ result i)) (i x (+ i z))) ((>= i y) result))) However, many Schemers find do loops to be distasteful.

问题 I am trying to multiply in Scheme using recursion, and I am able to do so with positive numbers but not negatives (they get stuck in an infinite loop). I assume the problem comes in the 3rd and 4th lines, which I wrote in an attempt to be able to handle negatives. Any help would be appreciated :) (define Multiply(lambda (x y) (if (eq? x 0) 0 (if (eq? y 0) 0 ;if either x or y are zero, return 0 (if (> 0 x) (- 0 (+ x (Multiply x (- y 1)))) (if (> 0 y) (- 0 (+ x (Multiply x (- y 1)))) (+ x

问题 I am trying to write a procedure that takes a a symbol and a list and inserts the symbol at every possible position inside the given list (thus generating a list of lists). I have coded the following definitions, which I must implement: 1 (define (insert-at pos elmt lst) (if (empty? lst) (list elmt) (if (= 1 pos) (cons elmt lst) (cons (first lst) (insert-at (- pos 1) elmt (rest lst)))))) 2 (define (generate-all-pos start end) (if (= start end) (list end) (cons start (generate-all-pos (+ start

问题 i'm new in scheme syntax. this is the last part of the project i've been working on. i was able to find the max from a giving Collatz sequence, but this part of the project requires finding the max length from a multiple Collatz sequences lists. So for example giving this list : '((1 10) (10 200) (201 210) (900 1000) and the output should be like this : ‘(20 125 89 174) i need to find the maximum length between the number 1 to 10 and then from 10 to 200 ets here is my code : #lang racket ;

问题 I am currently trying to define a function that takes a list of lists, models that list as a square matrix and returns the diagonal of said matrix. For example, input ((a b c) (d e f) (g h i)) gives (a e i) . I have a vague idea of how to go about solving this (taking the last element of the last list then the second to last element of the second to last list etc.) but I am not really sure of how to go about programming this in Scheme. I would appreciate it if somebody could point me in the

问题 Consider the following procedure taken from SICP: (define (make-withdraw balance) (lambda (amount) (if (>= balance amount) (begin (set! balance (- balance amount)) balance) "Insufficient funds"))) Suppose I say: (define x (make-withdraw 100)) make-withdraw returns a procedure ( (lambda (amount) ... ) ) inside a new environment called e2 (enclosing the binding for the variable balance ), and binds that procedure to x in the global frame. Now, say I call: (f x) where (define (f y) (y 25)) 1 . I

问题 I am having problem to print out all the possible paths. Currently I am only able to print out one path, and if (path-demo "J" "I"), the program will shown this error mcdr: expects argument of type <mutable-pair> ; given #f (define net '(("A" "B") ("B" "A" "C") ("C" "B" "D") ("D" "C" "E" "F") ("F" "I" "D") ("I" "F") ("E" "D" "J") ("J" "E" "G") ("G" "J" "H"))) (define (path-demo start finish) (for-each (lambda (x) (display x) (display " ")) (cons "Route:" (shortest-path start finish net))))

问题 So I am familiar with the algorithm for creating a power set using Scheme that looks something like this: (define (power-set set) (if (null? set) '(()) (let ((power-set-of-rest (power-set (cdr set)))) (append power-set-of-rest (map (lambda (subset) (cons (car set) subset)) power-set-of-rest))))) So this, for (1, 2, 3, 4), would output: (() (4) (3) (3 4) (2) (2 4) (2 3) (2 3 4) (1) (1 4) (1 3) (1 3 4) (1 2) (1 2 4) (1 2 3) (1 2 3 4)) I need to figure out how to output the power set "in order",

问题 The puzzle, implemented in Scheme, is as follows: (let* ((yin ((lambda (cc) (display #\@) cc) (call-with-current-continuation (lambda (c) c)))) (yang ((lambda (cc) (display #\*) cc) (call-with-current-continuation (lambda (c) c))))) (yin yang)) The goal of the puzzle is to work out and understand the output of this code. I'm wondering if it's possible to implement code with the same semantics using C# 5.0's new async CPS features. The part that I'm having trouble grasping, is that the puzzle