Question

I’m looking to take in a list with strings and numbers, such as

'("Ben" 95 99 100 -1 "Bob" 90 40 66 -5 "Jerry" 95 90 0) 

and return the list with all negative numbers removed and the name and its subsequent number values place inside of a list within that list – for my example, the wanted return value would be

(("Ben 95 99 100) ("Bob" 90 40 66) ("Jerry" 95 90 0))

I can’t get it to place the parentheses in the right places, and I’m wondering how this can be done. Can anyone help?

Answer 1

Try this:

(define (refactor lst acc)
  (cond ((empty? lst) (list acc))
        ((and (number? (first lst)) (< (first lst) 0))
         (cons acc (refactor (rest lst) '())))
        (else (refactor (rest lst) (append acc (list (first lst)))))))

When tested with the sample input provided:

(define lst '("Ben" 95 99 100 -1 "Bob" 90 40 66 -5 "Jerry" 95 90 0))
(refactor lst '())

The returned value is as expected:

(("Ben" 95 99 100) ("Bob" 90 40 66) ("Jerry" 95 90 0))