scheme

问题 Note: this is a bonus for homework, but I have spent way too long on trying things to no avail. Help is much appreciated, but not necessary I suppose. Premise: generate a powerset for a list of numbers, but without using any helpers, explicit recursion, looping, or functions/constants other than cons , first , rest , empty? , empty , else , lambda , and cond , while using only one define on the language level Intermediate Student with Lambda . The order of the powerset does not matter. What I

问题 Note: This is kind of homework, kind of not -- the end goal is to have a function that produces a powerset of a set of numbers supplied to the function as a list of numbers. I have a recursive version of the function but I now need to find some ways of replacing each explicitly recursive function in the solution I have ( append , mapm etc.) with an equivalent lambda-only expression. As such, I am starting with smaller problems and hope to combine them all to write a full function. I've

问题 Note: This is kind of homework, kind of not -- the end goal is to have a function that produces a powerset of a set of numbers supplied to the function as a list of numbers. I have a recursive version of the function but I now need to find some ways of replacing each explicitly recursive function in the solution I have ( append , mapm etc.) with an equivalent lambda-only expression. As such, I am starting with smaller problems and hope to combine them all to write a full function. I've

问题 Okay, I am new with scheme/racket/lisp. I am practicing creating my own functions, syntax, and recursion, so I want to make my own foldl and foldr functions that do exactly what the predefined versions do. I can't do it because I just don't understand how these functions work. I have seen similar questions on here but I still don't get it. Some examples broken down would help! Here is my (incorrect) process: (foldl - 0 '(1 2 3 4)) I do 0 -(4-3-2-1) and get 2 which is the right answer (foldl -

问题 Okay, I am new with scheme/racket/lisp. I am practicing creating my own functions, syntax, and recursion, so I want to make my own foldl and foldr functions that do exactly what the predefined versions do. I can't do it because I just don't understand how these functions work. I have seen similar questions on here but I still don't get it. Some examples broken down would help! Here is my (incorrect) process: (foldl - 0 '(1 2 3 4)) I do 0 -(4-3-2-1) and get 2 which is the right answer (foldl -

问题 I am trying to learn Scheme and I am having a hard time understanding the difference between map and apply . As I understand, map applies the function to each element of the list, and apply applies something to the arguments of a procedure. Can they be used interchangeably? 回答1: They are not the same! Their names can actually help remember which does what. map will take as argument one procedure and one or more lists. The procedure will be called once for each position of the lists, using as

问题 I am trying to learn Scheme and I am having a hard time understanding the difference between map and apply . As I understand, map applies the function to each element of the list, and apply applies something to the arguments of a procedure. Can they be used interchangeably? 回答1: They are not the same! Their names can actually help remember which does what. map will take as argument one procedure and one or more lists. The procedure will be called once for each position of the lists, using as

问题 Suppose I have the following tree: In my program, this tree is represented using a list: '(+ (* 5 6) (sqrt 3)) . How do I get a subtree by its index? The index should start from 0 and be depth-first. In the picture above, I have labelled all the nodes with their index to show this. For example: (define tree '(+ (* 5 6) (sqrt 3))) (subtree tree 0) ; Returns: '(+ (* 5 6) (sqrt 3))) (subtree tree 1) ; Returns: '(* 5 6) (subtree tree 2) ; Returns: 5 (subtree tree 3) ; Returns: 6 (subtree tree 4)

问题 Suppose I have the following tree: In my program, this tree is represented using a list: '(+ (* 5 6) (sqrt 3)) . How do I get a subtree by its index? The index should start from 0 and be depth-first. In the picture above, I have labelled all the nodes with their index to show this. For example: (define tree '(+ (* 5 6) (sqrt 3))) (subtree tree 0) ; Returns: '(+ (* 5 6) (sqrt 3))) (subtree tree 1) ; Returns: '(* 5 6) (subtree tree 2) ; Returns: 5 (subtree tree 3) ; Returns: 6 (subtree tree 4)

问题 Suppose I have the following tree: In my program, this tree is represented using a list: '(+ (* 5 6) (sqrt 3)) . How do I get a subtree by its index? The index should start from 0 and be depth-first. In the picture above, I have labelled all the nodes with their index to show this. For example: (define tree '(+ (* 5 6) (sqrt 3))) (subtree tree 0) ; Returns: '(+ (* 5 6) (sqrt 3))) (subtree tree 1) ; Returns: '(* 5 6) (subtree tree 2) ; Returns: 5 (subtree tree 3) ; Returns: 6 (subtree tree 4)