On Mon, May 24, 2010 at 4:22 PM, John Clements <cleme...@brinckerhoff.org> wrote: > > On May 24, 2010, at 1:11 PM, Matthew Flatt wrote: > >> At Mon, 24 May 2010 11:12:56 -0700, John Clements wrote: >>> Is there a good reason why port->lines doesn't close the input port? >> >> An eof-of-file doesn't necessarily mean an end-of-stream, and error >> handling usually requires extra effort to close a port, which is why we >> usually use functions like `with-input-form-file'. Probably, though, >> it's mostly that port-reading functions don't normally close the port. >> >>> Perhaps there >>> could be an optional argument that allowed this behavior? >> >> An optional keyword argument seems ok to me. > > > How about: > > (port->lines p #:close-on-eof? #t) > > implemented something like this: > > extra optional arguments in port.rkt: > ... > (define (port->lines [p (current-input-port)] #:line-mode [mode 'any] > #:close-on-eof? [close-on-eof? #f]) > (port->x-lines 'port->lines p mode read-line close-on-eof?)) > > (define (port->bytes-lines [p (current-input-port)] #:line-mode [mode 'any] > #:close-on-eof? [close-on-eof? #f]) > (port->x-lines 'port->bytes-lines p mode read-bytes-line close-on-eof?)) > ... > > additional explicit arg in portlines.rkt: > > (define (port->x-lines who p mode read-line close-on-eof?) > (unless (input-port? p) > (raise-type-error who "input-port" p)) > (check-mode who mode) > (let loop ([l null]) > (let ([line (read-line p mode)]) > (if (eof-object? line) > (begin0 (reverse l) > (when close-on-eof? > (close-input-port p))) > (loop (cons line l)))))) > > If this makes sense, I'll add docs (and a test case, if there are existing > rackety test cases for things like this). > > N.B.: Nothing here is committed yet, and I'm not proposing this for 5.0. > > John
John, If you want something consistent with existing functions, it sounds like a "with-input-from-url" would do what you want. We don't often have readers close a port, but we do have functions that open, use, and close a port all in one operation. --Carl _________________________________________________ For list-related administrative tasks: http://list.cs.brown.edu/mailman/listinfo/plt-dev
