scheme

问题 I am trying to translate some python code to scheme. def test(x): if x > 1: do something if x > 10: return if x == 4: do something test(11) I did not find the "return" in scheme. I want to quit from the test function when x >10. How can I simulate the "return" in scheme? (I am using guile) Thanks 回答1: In Scheme there isn't an explicit return keyword - it's a lot simpler than that, the value of the last expression in a sequence of expressions is the one that gets returned. For example, your

问题 having an issue with my perfect number function. The objective of the code is to determine if the number is a perfect number, meaning it is equal to the sum of its divisors. Ex:6. Im having trouble with my code. Here's my function: (define (is-perfect x) (define (divides a b) (= (modulo b a) 0)) (define (sum-proper-divisors y) (if (= y 1) 1 (if (divides y x) (+ y (sum-proper-divisors (- y 1))) (if (= x 1) #f (= (sum-proper-divisors (- x 1) x))))))) 回答1: You almost got it! there are a couple

问题 I want to do something like: (car '(. a)) and get . as a result. For example, if you type '. into the console you will get the output that I want. The problem is that I don't want to have an apostrophe infront of all of the . in a list. Any guidance? 回答1: In Scheme's read syntax, a standalone dot is special. '. won't get you a dot symbol; it's invalid syntax. (If it works in your implementation, then that's just a special quirk of your implementation.) Instead, you have to escape it. In most

问题 How would you define a function which takes one argument, which should be a list, and returns the elements in the list which are themselves lists? (check-expect (find-sublists ’(1 2 () (3) (a b c) a b c)) ’(() (3) (a b c))) 回答1: Do you have experience designing functions that can filter through a list? A simpler problem with the same flavor as the original is something like this: design a function that takes a list of numbers and keeps only the even numbers. Would you be able to do that

问题 I need to write a Scheme function (union s1 s2) that when given two sets, let's say s1 = ((1 3) (5 13) (25 100)) s2 = ((2 4) (17 26) (97 100)) will give (union s1 s2) ----> ((1 4) (5 13) (17 100)) Also if s1 = ((1 3) (5 13) (25 110) (199 300)) s2 = ((2 4) (17 26) (97 100) (110 200) (288 500)) then (union s1 s2) ----> ((1 4) (5 13) (17 500)) Can anybody suggest me how to do this? I have no idea how to start. 回答1: Instead of working with 2 sets, I would suggest merging the 2 sets into one

问题 I've written some code but it's not working because the add1 function I used in Scheme is not working with R5RS. What can replace add1 in R5RS? 回答1: The procedure add1 is very simple, you can implement it yourself: (define (add1 x) (+ x 1)) 回答2: late answer but an alternative is (making use of lambdas) .. (define add1 (lambda (x) (+ x 1))) 来源： https://stackoverflow.com/questions/13292094/add1-function-from-scheme-to-r5rs

问题 In Scheme or Racket is it possible to detect the caller of a function? For example, I can write a function to test if a list is a list of atoms as follows: (define atom? (lambda (x) (and (not (pair? x)) (not (empty? x))))) (define lat? (lambda (l) (define latt? (lambda (l) (cond ((null? l) #t) ((atom? (car l)) (latt? (cdr l))) (else #f)))) (if (null? l) #f (latt? l)))) but instead of the above, is there a function like "called-by" to do something like this: (define lat? (lambda (l) (cond (

问题 I'm currently looking into Scheme, and the way I have understood it, procedures can take an arbitrary number of arguments. I have been trying to play around with this, but I'm struggling to grasp the concept. For instance, say I want to write a welcome message, based on information provided by the user. If user provides a first and last name, the program shout write: Welcome, <FIRST> <LAST>! ;; <FIRST> = "Julius", <LAST>= "Caesar" Welcome, Julius Caesar! Otherwise, the program should refer to

问题 I'd like to know what this code means in Scheme: (define ((K x) y) x) (define (((S x) y) z) ((x z) (y z))) The whole file is here. Is this legal Scheme? Is (K x) a parametrized function, something like generic functions in Java? I looked up the MIT Scheme reference, there seems to be nothing mentioned for definition of this kind. 回答1: Trying it in MIT Scheme works (define ((K x) y) x) ;Value: k ((k 3) 4) ;Value: 3 Apparently, these are the definitions for K and S combinators from a

问题 Below is an attempt I've made to create a procedure that returns the function composition given a list of functions in scheme. I've reached an impasse; What I've written tried makes sense on paper but I don't see where I am going wrong, can anyone give some tips? ; (compose-all-rec fs) -> procedure ; fs: listof procedure ; return the function composition of all functions in fs: ; if fs = (f0 f1 ... fN), the result is f0(f1(...(fN(x))...)) ; implement this procedure recursively (define compose