On Sun, 14 Apr 2024, Matthew Kay wrote:
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Hi,
Short version of my question: Rf_applyClosure was marked
attribute_hidden in Oct 2023, and I am curious why and if there is an
alternative interface to it planned.
applyClosure has never been part of the API and was/is not intended
for use by packages. Keeping things like this internal is essential to
give us flexibility to make needed improvements to the basic engine.
Moving this out of the installed headers and marking it as not to be
exported merely clarifies that it is internal.
Long version:
I have been toying with building a package that makes it easier to do
non-standard evaluation directly using promises, rather than wrapping
these in a custom type (like e.g. rlang does). The advantage of this
approach is that it should be fully compatible with functions that use
the standard R functions for NSE and inspecting function context, like
substitute(), match.call(), or parent.frame(). And indeed, it works!
-- in R 4.3, that is. The prototype version of the package is here:
https://github.com/mjskay/uneval (the relevant function to my
question is probably do_invoke, in R/invoke.R).
While testing on R-devel, I noticed that Rf_applyClosure(), which used
to be exported, is now marked with attribute_hidden. I traced the
change to this commit in Oct 2023:
https://github.com/r-devel/r-svn/commit/57dbe8ad471c8a34314ee74362ad479db03c033a
However, the commit message did not give me clarity on the reason for
the change, and I have not been able to find mention of this change in
R-devel, R-package-devel, or the R bug tracker.
So, I am curious why this function is no longer exported and if there
is an alternative function planned to take its place.
Neither Rf_eval nor do.call can do what I need to fully support
rlang-style NSE using base R. The problem is that I need to be able to
manually set up the list of promises provided as arguments to the
function.
I fully understand that the answer to my question might be "don't do
that" ;).
That would be my advice: Don't do that. The API does not provide an
interface for working with promises; in fact the existence of promises
is not guaranteed in the future. Some packages have unfortunately made
use of some internal functions related to promises. For the ones on
CRAN we will work with the maintainers to find alternate
approaches. This may mean adding some functions to the API for dealing
with some lazy-evaluation-related features at a higher level.
Best,
luke
But I will humbly suggest that it would be really nice to be
able to do NSE that can capture expressions with heterogeneous
environments and pass these to functions in a way that is compatible
with existing R functions that do NSE. The basic tools to do it are
there in R 4.3, I think...
Thanks for the help!
---Matt
--
Matthew Kay
Associate Professor
Computer Science & Communication Studies
Northwestern University
matthew....@u.northwestern.edu
http://www.mjskay.com/
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--
Luke Tierney
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-tier...@uiowa.edu
Iowa City, IA 52242 WWW: http://www.stat.uiowa.edu/
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