return value of `string-set!'

[Alexandru Cojocaru]

Hi,
currently `string-set!' returns an unspecified value. What about making 
it return `str' instead?

Here is an example of its use:

; make a copy of `str' and replace its first character with `#\a'
(define (make-copy str)
 (string-set! (string-copy str) 0 #\a))

instead of:

(define (make-copy str)
 (let ((s (string-copy str)))
  (begin
    (string-set! s 0 #\a)
    s)))

or perhaps I am doing something wrong?

PS: the documentation of `list-set!' doesn't say what's its return value.

Best regards,
Alexandru Cojocaru