How do I change the list using mutable lists in Racket or Scheme?

Posted by exOne on Stack Overflow See other posts from Stack Overflow or by exOne
Published on 2011-01-18T00:57:11Z Indexed on 2011/01/18 2:53 UTC
Read the original article Hit count: 199

Filed under:

Scheme

|

racket

I need your help Can anyone help me?

first question

This procedure should modify each element which’s index in the list is even. The value of the element should be equal to the new-element. For example: (define number-list (1 56 8 1 43 9 78)) (modify-even-indices number-list 10) The new list: 1 10 8 10 43 10 78

second question

This problem is the extended version of Question 1.

(modify-even-odd-indices my-list new-element modification-type) This procedure should modify each element according to the modification-type. The modification-type can be even or odd. For example: (define number-list (1 56 8 1 43 9 78)) (modify-even-odd-indices number-list 10 ‘even’) The new list: 1 10 8 10 43 10 78 (modify-even-odd-indices number-list 10 ‘odd’) The new list: 10 56 10 1 10 9 10

© Stack Overflow or respective owner

Related posts about Scheme

About "If.." in Scheme (plt-scheme)

as seen on Stack Overflow - Search for 'Stack Overflow'
I had a pretty simple requirement in my Scheme program to execute more than one statement, in the true condition of a 'if'. . So I write my code, something like this: (if (= 1 1) ((expression1) (expression2)) ; these 2 expressions are to be executed when the condition is true (expression3)… >>> More
Detecting EOF in a Binary File using Scheme

as seen on Stack Overflow - Search for 'Stack Overflow'
(define (read-all-input) (local ((define line (bytes->list (read-bytes 4)))) (if (eof-object? line) empty (cons line (read-all-input))))) (void (read-all-input)) The above code fails because bytes-list expects an argument of type byte string, but is given # >>> More
Scheme: Detecting duplicate elements in a list

as seen on Stack Overflow - Search for 'Stack Overflow'
Does R6RS or Chez Scheme v7.9.4 have a library function to check if a list contains duplicate elements? Alternatively, do either have any built in functionality for sets (which dis-allow duplicate elements)? So far, I've only been able to find an example here. The problem with that is that it doesn't… >>> More
Scheme implementations - what does it mean?

as seen on Stack Overflow - Search for 'Stack Overflow'
Hi, I'm a beginning student in CS, and my classes are mostly in Java. I'm currently going through "Little Schemer" as a self study, and in the process of finding out how to do that I have found numerous references to "implementations" of Scheme. My question is, what are implementations? Are they… >>> More
Traversing Scheme function as a list

as seen on Stack Overflow - Search for 'Stack Overflow'
Isn't it possible to treat functions in Scheme as any other list? Basically, what I want do to is something like this: (define (foo) "hello") (cdr foo) ; or similar, should return the list ((foo) "hello") I've found a similar discussion about this, and I feel a bit disappointed if this is not… >>> More

Related posts about racket

Racket list in struct

as seen on Stack Overflow - Search for 'Stack Overflow'
I just started programming with Racket and now I have the following problem. I have a struct with a list and I have to add up all prices in the list. (define-struct item (name category price)) (define some-items (list (make-item "Book1" 'Book 40.97) (make-item "Book2" 'Book 5.99) (make-item… >>> More
racket scheme get-argb-pixels

as seen on Stack Overflow - Search for 'Stack Overflow'
I have a 32 by 32 pixel png file. I'm trying to read the values within it using get-argb-pixels. My code is as follows: #lang racket/gui (require racket/gui/base) (define floor (make-object bitmap% "C:\\floortile.png")) (define pixels (make-bytes (* 32 32 4))) (send floor get-argb-pixels 0… >>> More
Racket: change dotted pair to list

as seen on Stack Overflow - Search for 'Stack Overflow'
I have a program that recursively calls a hashtable and prints out data from it. Unfortunately my hashtable seems to be saving data as dotted pairs so when I call the hashtable I get an error saying that there is no data for it because its tryign to search the hashtable for a dotted pair instead… >>> More
Using hash tables in racket

as seen on Stack Overflow - Search for 'Stack Overflow'
Im working on an Ngrams program and im having trouble filling out my hash table. i want to write out a recursive function that will take the words and add them to the hash table. The way its supposed to work is given the data set 1 2 3 4 5 6 7 the first entry in the hash table should have a key… >>> More
If Scheme is untyped, how can it have numbers and lists?

as seen on Programmers - Search for 'Programmers'
Scheme is said to be just an extension of the Untyped Lambda Calculus (correct me if I am wrong). If that is the case, how can it have Lists and Numbers? Those, to me, look like 2 base types. So I'd say Racket is actually an extension of the Simply Typed Lambda Calculus. No? Question: Is Scheme's… >>> More