Re: with-open-stream and with-open-file

[Pavel.pa@Xerox.COM]

	Date: Fri, 16 Oct 87 11:33 EDT
	From: David C. Plummer <DCP@QUABBIN.SCRC.Symbolics.COM>

	CLtL says that the stream (file) scoped by with-open-stream
	(with-open-file) is closed when the form is exited, independent of
	exit-reason.  I would like people to consider the following allowance:
	that if the stream variable is NIL during the close operation, then the
	stream (file) is not closed.  Thus
		(with-open-stream (stream constructor)
		  (prog1 stream (setq stream nil)))
	would evaluate to an open stream.

	[More language supporting the above as an idiom.]

Surely I'm misunderstanding you.  Why use the above form instead of
simply `constructor'?  It must be that you mean to do more stuff before
the prog1, perhaps to "set up" the stream and/or some other structures
concerned with it.  The idea would be to have the implicit
unwind-protect around those set-up forms and then be able to leave the
unwind-protect with the stream still open.  Have I properly understood
your intent?

If so, then I must say that I would find the form you describe far less
clear than the equivalent explicit unwind-protect.  In general, I
dislike forms that pass information to invisible parts by the setting of
a lexical variable.  The information path is just too hidden.

	Pavel