On 10/26/2006 6:28 AM, Philippe Grosjean wrote:
>
>> On 10/26/06, Duncan Murdoch <[EMAIL PROTECTED]> wrote:
> [...]
>>> Actually, there is a way, but it's undocumented (i.e., use at your own
>>> risk). It's the eval.with.vis function. This is an internal function
>
> Yes... and there are three problems here:
> 1) To spot the undocumented function one is looking for,
> 2) To figure out how to use it,
> 3) To rewrite your code regularly if you maintain packages that use
> several of such undocumented functions. This is the case of many R GUI
> projects... and one reason why staying up-to-date with the new versions
> of R (every 6 months) is a nightmare for these GUIs!
Those are definitely real problems.
At the last useR meeting, Thomas Baier made an excellent suggestion:
someone should put together an API specifically for R GUIs. I think
eval.with.vis would have to be part of such an API; there are dozens of
other currently undocumented or unavailable functions as well.
This is a difficult project, because it would have to get agreement on
what should be part of the API, and that will constrain future changes:
so there would be a lot of resistance to making it too constraining.
It will need to be flexible, so that R isn't required to supply services
that don't make sense in all contexts.
Duncan Murdoch
> For instance, I use eval.with.vis() in the latest version of svSockets
> package in the SciViews bundle, but I am afraid to release it on CRAN
> because I know of the nightware I will face if this function (silently)
> changes its behavior in subsequent versions of R.
>
> I guess there is no solution to this problem, since there is certainly a
> good reason for keeping portions of R code undocumented (and thus
> flagged as :" use-it-at-your-own-risk!"), but it does not eases our life!
>
> Best,
>
> Philippe Grosjean
>
>>> that is used within source() and capture.output(); you'll have to guess
>>> from the usage there what the args are. But here's an F that does
>>> something close to what you want:
>>>
>>> > fix(F)
>>> > f <- function() 1
>>> > g <- function() invisible(1)
>>> >
>>> > F <- function (expr)
>>> + {
>>> + expr <- substitute(expr)
>>> + pf <- parent.frame()
>>> + tmp <- .Internal(eval.with.vis(expr, pf,
>>> + baseenv()))
>>> + tmp
>>> + }
>>> > F(f())
>>> $value
>>> [1] 1
>>>
>>> $visible
>>> [1] TRUE
>>>
>>> > F(g())
>>> $value
>>> [1] 1
>>>
>>> $visible
>>> [1] FALSE
>>>
>>>
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