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Re: Issue: CLOSED-STREAM-OPERATIONS (Version 4)
- To: Kent M Pitman <KMP@stony-brook.scrc.symbolics.com>
- Subject: Re: Issue: CLOSED-STREAM-OPERATIONS (Version 4)
- From: masinter.pa@Xerox.COM
- Date: 1 Dec 88 16:58 PST
- Cc: CL-Cleanup@sail.stanford.edu
- In-reply-to: Kent M Pitman <KMP@stony-brook.scrc.symbolics.com>'s message of Thu, 1 Dec 88 15:21 EST
In the implementations I've been most familiar with, INPUT-STREAM-P and
OUTPUT-STREAM-P are predicates on state rather than on "class".
That is, a "stream" can have one of several states: closed, open for input,
open for output, open for both input/output.
CLOSE transitions a stream from one of the "open" states to one to the
closed state.
Well, anyway, that's how I think of it. In Interlisp, OPENP was the
predicate, you could ask just (OPENP x) or (OPENP x 'INPUT) or (OPENP X
'OUTPUT) or (OPENP X 'BOTH).