From mel at altk.com  Fri Jun  1 08:24:14 2007
From: mel at altk.com (mel)
Date: Fri, 01 Jun 2007 08:24:14 +0200
Subject: [Rd] Possible changes to connections
In-Reply-To: <Pine.LNX.4.64.0705311534280.27499@gannet.stats.ox.ac.uk>
References: <Pine.LNX.4.64.0705301726400.11532@gannet.stats.ox.ac.uk>
	<465E7B0B.2080005@altk.com>
	<Pine.LNX.4.64.0705311534280.27499@gannet.stats.ox.ac.uk>
Message-ID: <465FBB8E.1040400@altk.com>

Prof Brian Ripley a ?crit :

>> I use getConnection().
>> In the context in which I use it, the number of the connection is
>> known a priori.
> 
> I don't see how you can know it 'a priori': it is an implementation detail
> (and since R itself uses connections, those details could easily change).

(disclaimer : I don't claim its the best way to proceed)

Before launching my app, the connections context is :
 > showConnections(all=TRUE)
   description class      mode text   isopen   can read can write
0 "stdin"     "terminal" "r"  "text" "opened" "yes"    "no"
1 "stdout"    "terminal" "w"  "text" "opened" "no"     "yes"
2 "stderr"    "terminal" "w"  "text" "opened" "no"     "yes"

So, the call to socketConnections() creates always (at least
for all my experiments) a connection with number 3.
Btw, if (socketConnections(...) != 3) the application simply
don't launch.
So, if the application runs, it's sure that this is with a
connection number==3.
That's why I say that "the number of the connection is known a priori".

Of course, the connection number could also be retrieved eg using
the description field.



[Rd] Possible changes to connections
mel