Sum base-10 digits of number in racket

test.rkt

#lang racket

;; Racket is a trip

;; ASCI-Value minus 48
(define (parseDigit c)
    (- (char->integer c) 48))

;; Sums a list of characters as integers
(define (addDigitString charList)
    (cond 
        [(= 1 (length charList)) 
         (parseDigit (first charList))]
        [ else ( + 
                (parseDigit (first charList)) 
                (addDigitString (rest charList)))]
    )
)

;; Sums the base-10 digits of a number
(define (addDigits num)
    (addDigitString (string->list (number->string num))))


(addDigits 123);; 6