[Rd] Inconsistency in creating/opening/closing/destroying
Prof Brian D Ripley
Wed, 20 Dec 2000 13:14:56 +0000 (GMT)
On Wed, 20 Dec 2000 email@example.com wrote:
> I expected close() to be the opposite of open(), but
Why? It is not documented to be so, as far as I know.
> > # create a connection
> > con <- file("ex.data")
> > # open it
> > open(con, "w")
> > # close it
> > close(con)
> > # re-open it
> > open(con, "w")
> Error in open.connection(con, "w") : invalid connection
> > con
> Error in summary.connection(x) : invalid connection
> > # is obviously pointing to a non-existing connection
> help to showConnections obviously also was assuming that there may EXIST something like a CLOSED connection, as it says
> all logical: if true all connections, including CLOSED ONES and the standard ones are displayed. If false only open user-created connections are included.
> So this is at least a documentation bug, but what about having something like
Can you please elucidate here? I don't think any documentation says
open is the opposite of close. I think you are just assuming things that
are not said. Note: ?close says
`close' closes and destroys a connection.
not just closes it, so there can be closed and not destroyed connections.
> Is there any reason to have (as currently) OpenConnection seperated from CreateConnection but CloseConnection and DestroyConnection combined?
Yes. These are S4-type connections, and that is what S4 does.
Brian D. Ripley, firstname.lastname@example.org
Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/
University of Oxford, Tel: +44 1865 272861 (self)
1 South Parks Road, +44 1865 272860 (secr)
Oxford OX1 3TG, UK Fax: +44 1865 272595
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