[Rd] Inconsistency in creating/opening/closing/destroying connections (PR#787)

[Prof Brian D Ripley]

On Wed, 20 Dec 2000 joehl@web.de 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.

> CreateConnection
>   OpenConnection
>   CloseConnection
> DestroyConnection
> 
> 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,                  ripley@stats.ox.ac.uk
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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