;;;;
;;;; Standard strings in Scheme are immutable.  There seems to be one
;;;; relatively easy ways around this problem:
;;;;
;;;;     1) Use what C++ would call an ostringstream:
;;;;
;;;;            (define s (open-output-string))
;;;;            (display "Hello, World!" s)
;;;;            (newline s)
;;;;            (display "Goodbye, Cruel World!" s)
;;;;            (newline s)
;;;;            (get-ouput-string s)
;;;;
;;;; Also see the dstring2.scm file for an equivalent class that is
;;;; implemented using lists of characters instead.
;;;;
;;;; WARNING: This implementation depends on open-output-string which
;;;; is not standard, but is available in at least chicken, guile, and
;;;; mzscheme.  If your scheme interpreter does not support
;;;; open-output-string, use the implementation in dstring2.scm which
;;;; is based on lists and should be portable to any scheme
;;;; interpreter.
;;;;

(define (dstring)
  (open-output-string))

(define (dstring->string s)
  (get-output-string s))

(define (dstring->list s)
  (string->list (dstring->string s)))

(define (dstring-append s x)
  (display x s))

(define (dstring-append-char s c)
  (display c s))

(define (dstring-append-line s . args)
  (if (not (null? args))
      (display (car args) s))
  (newline s))

;;(define (dstring-clear s)
;;  (file-position s 0))