[R] setting options only inside functions

[luke-tierney at uiowa.edu]

The Python solution does not extend, at least not cleanly, to things
like dev on/ dev off or to Hadley's locale example.  In any case if I
am reading the Python source correctly on how they handle user
interrupts this solution has the same non-robusness to user interrupts
issue that Bill's initial solution had.

As a basis I believe what we need is a mechanism that handles a
setup, an action, and a cleanup, with setup and cleanup occurring with
interrupts disablednand the action with interrupts enabled. Scheme's
dynamic wind is similar, though I don't believe the scheme standard
addresses interrupts and we don't need to worry about continuations,
but some of the issues are similar.  Probably we would want two
flavors, one in which the action has to be a function that takes as a
single argument the result produced by the setup code, and one in
which the action can be an argument expression that is then evaluated
at the appropriate place by laze evaluation.

This can be done at the R level except for the controlling of
interrupts (and possibly other asynchronous stuff)-- that would need a
new pair of primitives (suspendInterrupts/enableInterupts or something
like that).  There is something in the Haskell literature on this that
I have looked at a while back -- probably time to have another look.


On Thu, 28 Apr 2011, Jonathan Daily wrote:

> I would also love to see this implemented in R, as my current solution
> to the issue of doing tons of open/close, dev/dev.off, etc. is to use
> snippets in my IDE, and in the end I feel like it is a hack job. A
> pythonic "with" function would also solve most of the situations where
> I have had to use awkward try or tryCatch calls. I would be willing to
> help with this project, even if it is just testing.
>
> On Wed, Apr 27, 2011 at 5:43 PM, Barry Rowlingson
> <b.rowlingson at lancaster.ac.uk> wrote:
>>> but it's a little clumsy, because
>>>
>>> with_connection(file("myfile.txt"), {do stuff...})
>>>
>>> isn't very useful because you have no way to reference the connection
>>> that you're using. Ruby's blocks have arguments which would require
>>> big changes to R's syntax.  One option would to use pronouns:
>>
>>  Looking very much like python 'with' statements:
>>
>> http://effbot.org/zone/python-with-statement.htm
>>
>>  Implemented via the 'with' statement which can operate on anything
>> that has a __enter__ and an __exit__ method. Very neat.
>>
>> Barry
>>
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>>
>
>
>
>

-- 
Luke Tierney
Statistics and Actuarial Science
Ralph E. Wareham Professor of Mathematical Sciences
University of Iowa                  Phone:             319-335-3386
Department of Statistics and        Fax:               319-335-3017
    Actuarial Science
241 Schaeffer Hall                  email:      luke at stat.uiowa.edu
Iowa City, IA 52242                 WWW:  http://www.stat.uiowa.edu