How do I find the number of lower case letters in Scheme Racket?

Question

I'm trying to find the number of lower/upper case letters in a string, but there is a problem with my code:

(define case
  (lambda (list)
    (if(char-lower-case? (car list))
       (case (cdr list))
       (+ 1 (case (cdr list)))
       )
    ))

(case (string->list "ScheMe"))

How can I solve this problem?

Answer 1

In your function you have two problems:

1. case is a predefined operator in racket/scheme

2. You don't test for an empty list.

Moreover, you use the parameter list, which is a primitive operator and should not be used as variable name.

Here is a working function:

(define (case1 lst)
    (cond ((null? lst) 0)
          ((char-lower-case? (car lst)) (case1 (cdr lst)))
          (else (+ 1 (case1 (cdr lst))))))

(case1 (string->list "ScheMe"))