Question

If I define a list in scheme like this

(define list '(when i type I 1 23 4 2))

What’s the type of the thing (car list) returns? And another question is: can I convert it to the string?

Answer 1

In the list shown in the question, the car is the symbol 'when. You can verify it, but first let’s change the name of the list to something else, for avoiding a name collision with the built-in list procedure:

(define lst '(when i type I 1 23 4 2))
(symbol? (car lst))
> #t

The #t (true) in the last line shows that indeed the first element is a symbol. If you need to convert it to a string, simply do this:

(symbol->string (car lst))
> "when"

EDIT :

Answering the question in the comments, this should work:

(define (isvariable? symbol)
  (and (symbol? symbol)
       (eqv? (string-ref (symbol->string symbol) 0)
               #\?)))