Question

so i’m trying to write a procedure known as sort-nums so that i can get all the numbers and sort them like this

(define (sort-nums lst)
(if (null? lst) null
(if (number? (car lst)
i want this part to keep the number and then delete anything that isnt a number
(sort (cons (car lst) (sort-nums (cdr lst))))))

if possible would this work or would i need to write it in a different way an example to prove that it works would be like

(sort-nums (list ‘a ‘c 24 ‘f ‘g 16))
(16 24)

Answer 1

You can make your life easier by sorting and stripping numbers separately. Try

(sort (list-transform-positive '(a 2 b 1) 
                               number?) 
       <)

First we select only those things that are numbers (using list-transform-positive), then we sort them ascending (using sort).

As a general tip, you will find lisp much easier to work with if you indent intelligently.