[plt-scheme] peek-char skip behavior

On Wed, Jun 14, 2006 at 12:17:08AM -0400, David T. Pierson wrote:
> I would like to skip chars.  I don't see a built-in function for doing
> this, so here's an attempt at rolling my own.  Comments welcome.

Of course I realize after sending that my tests did not include a skip-k
beyond eof.  Here's an implementation that checks for eof:

(define (peek-char/skip-chars iport skip-k)
  (let loop ((chars-to-skip skip-k)
             (bytes-to-skip 0))
    (let ((c (peek-char iport bytes-to-skip)))
      (cond
        ((eof-object? c)
         c)
        ((= 0 chars-to-skip)
         c)
        (else
         (loop (- chars-to-skip 1)
               (+ bytes-to-skip (char-utf-8-length c))))))))

David