Racket\Scheme compare and delete unwanted items in a list

Question

I have 2 lists:

(Define list1 '("xx1" "xx2" xx3" "xx4" "xx5"))
(Define list2 '("xx2" "xx4" "xx5"))

the items in the list above are just an example, but either way it will be a string item. What I need to do is compare both lists and remove the items in list1 that are found in list2.

is there a short map routine i can do?

this isn't some homework project, I wish there was a course here for programming classes though :/

possible duplicate of [Common elements in two lists with duplicates](http://stackoverflow.com/questions/18152062/common-elements-in-two-lists-with-duplicates) — Crembo, Jun 11 '15 at 09:52
Programming class following Racket language: [How to design programs](http://www.htdp.org/). Scheme standard [SICP](http://mitpress.mit.edu/sicp/full-text/book/book.html) and a [video course](https://www.youtube.com/watch?v=2Op3QLzMgSY&list=PL8FE88AA54363BC46) by the magicians on MIT opencourseware (R4RS, but mostly compatible with todays Scheme and `#!racket`. There is a [SICP compability package](http://stackoverflow.com/a/25096066/1565698)) — Sylwester, Jun 11 '15 at 14:28

score 1 · Answer 1 · answered Jun 12 '15 at 07:48

1

There's also remove*

An example:

#lang racket
(define list1 '("xx1" "xx2" "xx3" "xx4" "xx5"))
(define list2 '("xx2" "xx4" "xx5"))

(displayln (remove* list2 list1))

Prints:

(xx1 xx3)

answered Jun 12 '15 at 07:48

minikomi

8,363
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score 0 · Accepted Answer · answered Jun 11 '15 at 09:59

0

#lang racket
(define list1 '("xx1" "xx2" "xx3" "xx4" "xx5"))
(define list2 '("xx2" "xx4" "xx5"))

(for/list ([x (in-list list1)]
           #:unless (member x list2))
  x)

Result:

 '("xx1" "xx3")

answered Jun 11 '15 at 09:59

soegaard

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4
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Racket\Scheme compare and delete unwanted items in a list

2 Answers2