[Rd] :: and ::: as .Primitives?

[Peter Haverty]

Hi all,

I use Luke's "::" hoisting trick often. I think it would be fantastic
if the JIT just did that for you.

The main trouble, for me, is in code I don't own.  When common
Bioconductor packages are loaded many, many base functions are saddled
with this substantial dispatch and "::" overhead.

While we have the hood up, the parser could help out a bit here too.
It already has special cases for "::" and ":::". Currently you get the
symbols "pkg" and "name" and have to go fishing in the calling
environment for the associated values.  It would be nice to have the
parser or JIT rewrite base::match as doubleColon("base","match") or
directly provide the symbols "base" and "match" to the subsequent
code.

I think it's also kind of entertaining that the comments in
base/R/namespace.R note that they are using ":::" for speed purposes
only.
Pete

____________________
Peter M. Haverty, Ph.D.
Genentech, Inc.
phaverty at gene.com


On Thu, Jan 22, 2015 at 12:54 PM, Michael Lawrence
<lawrence.michael at gene.com> wrote:
> On Thu, Jan 22, 2015 at 11:44 AM,  <luke-tierney at uiowa.edu> wrote:
>>
>> For default methods there ought to be a way to create those so the
>> default method is computed at creation or load time and stored in an
>> environment.
>
> We had considered that, but we thought the definition of the function
> would be easier to interpret if it explicitly specified the namespace,
> instead of using tricks with environments. The same applies for
> memoizing the lookup in front of a loop.
>
> The implementation of these functions is almost simpler in C than it
> is in R, so there is relatively little risk to this change. But I
> agree the benefits are also somewhat minor.
>
>> For other cases if I want to use foo::bar many times, say
>> in a loop, I would do
>>
>> foo_bar <- foo::bar
>>
>> and use foo_bar, or something along those lines.
>>
>> When :: and ::: were introduce they were intended primarily for
>> reflection and debugging, so speed was not an issue. ::: is still
>> really only reliably usable that way, and making it faster may just
>> encourage bad practice. :: is different and there are good arguments
>> for using it in code, but I'm not yet seeing good arguments for use in
>> ways that would be performance-critical, but I'm happy to be convinced
>> otherwise. If there is a need for a faster :: then going to a
>> SPECIALSXP is fine; it would also be good to make the byte code
>> compiler aware of it, and possibly to work on ways to improve the
>> performance further e.g. through cacheing.
>>
>> Best,
>>
>> luke
>>
>>
>> On Thu, 22 Jan 2015, Peter Haverty wrote:
>>
>>
>>> Hi all,
>>>
>>> When S4 methods are defined on base function (say, "match"), the
>>> function becomes a method with the body "base::match(x,y)". A call to
>>> such a function often spends more time doing "::" than in the function
>>> itself.  I always assumed that "::" was a very low-level thing, but it
>>> turns out to be a plain old function defined in base/R/namespace.R.
>>> What would you all think about making "::" and ":::" .Primitives?  I
>>> have submitted some examples, timings, and a patch to the R bug
>>> tracker (https://bugs.r-project.org/bugzilla3/show_bug.cgi?id=16134).
>>> I'd be very interested to hear your thoughts on the matter.
>>>
>>> Regards,
>>> Pete
>>>
>>> ____________________
>>> Peter M. Haverty, Ph.D.
>>> Genentech, Inc.
>>> phaverty at gene.com
>>>
>>> ______________________________________________
>>> R-devel at r-project.org mailing list
>>> https://stat.ethz.ch/mailman/listinfo/r-devel
>>>
>>
>> --
>> 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-tierney at uiowa.edu
>> Iowa City, IA 52242                 WWW:  http://www.stat.uiowa.edu
>>
>>
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