Re: [Rd] Capturing environment associated with a promise
> Both of these are possible in C. See: > > https://stat.ethz.ch/pipermail/r-devel/2007-September/046943.html Cool, thanks. > It shows how to query an object to see if its a promise and but rather > than extract the environment it shows how to copy a promise without > evaluating it; however, it was also my experience that these two were > what was actually needed rather than being able to extract the > environment. > > I would also recommend you do some testing since I found that adding > promises did not always make as big a difference in performance as I > had hoped and the added complexity may not be worth it in all cases. > For example, I had a version of proto that supported promises but > ggplot2 only ran slightly faster with it so I did not pursue it any > further. On the other hand if you are doing it to support > self-referential structures then that is a different matter. I'm mainly interested in this for pedagogy - giving students some tools to inspect promises without evaluating them would be useful. Hadley -- RStudio / Rice University http://had.co.nz/ __ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
Re: [Rd] Capturing environment associated with a promise
> Promises are an implementation detail -- we need to be able to change > them, optimize them away, etc, so there is a limit on what we want to > expose. Allowing a query of whether a binding is delayed or not > should be OK but would want to think that through more carefully > before committing to this. Ok, thanks. Hadley -- RStudio / Rice University http://had.co.nz/ __ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
Re: [Rd] Capturing environment associated with a promise
On Mon, Oct 8, 2012 at 9:22 AM, Hadley Wickham wrote: > Hi all, > > It's possible to capture the expression associated with a promise > (using substitute). Is there any way to capture the environment > associated with a promise? Similarly, is there any way to tell if > something is a promise without accidentally evaluating it? > Both of these are possible in C. See: https://stat.ethz.ch/pipermail/r-devel/2007-September/046943.html It shows how to query an object to see if its a promise and but rather than extract the environment it shows how to copy a promise without evaluating it; however, it was also my experience that these two were what was actually needed rather than being able to extract the environment. I would also recommend you do some testing since I found that adding promises did not always make as big a difference in performance as I had hoped and the added complexity may not be worth it in all cases. For example, I had a version of proto that supported promises but ggplot2 only ran slightly faster with it so I did not pursue it any further. On the other hand if you are doing it to support self-referential structures then that is a different matter. -- Statistics & Software Consulting GKX Group, GKX Associates Inc. tel: 1-877-GKX-GROUP email: ggrothendieck at gmail.com __ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
Re: [Rd] Capturing environment associated with a promise
Promises are an implementation detail -- we need to be able to change them, optimize them away, etc, so there is a limit on what we want to expose. Allowing a query of whether a binding is delayed or not should be OK but would want to think that through more carefully before committing to this. luke On Mon, 8 Oct 2012, Hadley Wickham wrote: Hi all, It's possible to capture the expression associated with a promise (using substitute). Is there any way to capture the environment associated with a promise? Similarly, is there any way to tell if something is a promise without accidentally evaluating it? Thanks! Hadley -- Luke Tierney Chair, Statistics and Actuarial Science Ralph E. Wareham Professor of Mathematical Sciences University of Iowa Phone: 319-335-3386 Department of Statistics andFax: 319-335-3017 Actuarial Science 241 Schaeffer Hall email: luke-tier...@uiowa.edu Iowa City, IA 52242 WWW: http://www.stat.uiowa.edu __ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
Re: [Rd] Capturing environment associated with a promise
On 12-10-08 9:22 AM, Hadley Wickham wrote: Hi all, It's possible to capture the expression associated with a promise (using substitute). Is there any way to capture the environment associated with a promise? Similarly, is there any way to tell if something is a promise without accidentally evaluating it? Neither of those is possible in user-level code. The special functions get to see their arguments unevaluated, but users can't write specials, and there is no special to extract an environment from a promise. I think the reasoning is that it keeps the semantics simpler, but I can't remember the cases that make user-level promise handling problematic. Duncan Murdoch __ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
[Rd] Capturing environment associated with a promise
Hi all, It's possible to capture the expression associated with a promise (using substitute). Is there any way to capture the environment associated with a promise? Similarly, is there any way to tell if something is a promise without accidentally evaluating it? Thanks! Hadley -- RStudio / Rice University http://had.co.nz/ __ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
