R devel - Jul 2007 - Hook for running a function before evaluation

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
( ( ( ( (
..............................................................

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
> ( ( ( ( (
> ..............................................................
>
> ______________________________________________
> R-devel at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-devel
>

-- 
Byron Ellis (byron.ellis at gmail.com)
"Oook" -- The Librarian