From byron.ellis at gmail.com  Fri Jul  6 21:05:01 2007
From: byron.ellis at gmail.com (Byron Ellis)
Date: Fri, 6 Jul 2007 12:05:01 -0700
Subject: [Rd] Hook for running a function before evaluation
In-Reply-To: <468E4068.8020203@sciviews.org>
References: <468E4068.8020203@sciviews.org>
Message-ID: <7098abec0707061205p579157b3w64b55dd7c84e14a2@mail.gmail.com>

Hi Philippe,

This is exactly the approach being taken in RExecServer (which is in
turn possibly connected to front ends via distributed objects). It's
an OS X app so the model is

my_ReadConsole(...) {
 didFinishEvaluationForInterpreter(...);
 internalReadConsole(...); (usually start the run loop and wait for an
appropriate event)
 willBeginEvaluationForInterpreter(...);
}

technically there should also be shouldBeginEvaluationforInterpreter()
to let us bail out of evaluation and head back to the reader loop.

http://repo.or.cz/w/RExecServer.git

On 7/6/07, Philippe Grosjean <phgrosjean at sciviews.org> wrote:
> Hello,
> I like much addTaskCallback() and friends. However, there are situations
> were we would like to have a function run BEFORE, not after every
> top-level tasks. I think specifically to reset options(width = ) to
> accommodate to the current width of the console, using something like:
>
> options(width = system("tput cols"))
>
> I am sure there are many other situations where this could be useful.
> Combining tasks run before and after evaluation, one could design a
> system to (remotely) indicate when a given R kernel is
> starting/evaluating/ending evaluation of some code (with Rpad in mind,
> for instance).
>
> How difficult would it be to implement such Tasks run before top-level ones?
>
> Best,
>
> Philippe
> --
> ..............................................<?}))><........
>   ) ) ) ) )
> ( ( ( ( (    Prof. Philippe Grosjean
>   ) ) ) ) )
> ( ( ( ( (    Numerical Ecology of Aquatic Systems
>   ) ) ) ) )   Mons-Hainaut University, Belgium
> ( ( ( ( (
> ..............................................................
>
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-- 
Byron Ellis (byron.ellis at gmail.com)
"Oook" -- The Librarian



[Rd] Hook for running a function before evaluation
Byron Ellis