“typeof” is your friend here: > typeof(`[`) [1] "special" > typeof(mc[[1]]) [1] "symbol" > typeof(mc2[[1]]) [1] "special"
so mc[[1]] is a symbol, and thus not a primitive. - Lukas > On 28 Mar 2017, at 14:46, Michael Lawrence <lawrence.mich...@gene.com> wrote: > > There is a difference between the symbol and the function (primitive > or closure) to which it is bound. > > This: > mc2 <- as.call(list(`[`,iris,2,"Species")) > > Evaluates `[` to its value, in this case the primitive object, and the > primitive itself is incorporated into the returned call. > > If you were to do this: > mc2 <- as.call(list(quote(`[`),iris,2,"Species")) > > The `[` would _not_ be evaluated, quote() would return the symbol, and > the symbol would end up in the call. > > The two forms have virtually identical behavior as long as the call > ends up getting evaluated in the same environment. > > On Tue, Mar 28, 2017 at 3:03 AM, Joris Meys <jorism...@gmail.com> wrote: >> Dear, >> >> I have noticed this problem while looking at the following question on >> Stackoverflow : >> >> http://stackoverflow.com/questions/42894213/s4-class-subset-inheritance-with-additional-arguments >> >> While going through callNextMethod, I've noticed the following odd >> behaviour: >> >> mc <- call("[",iris,2,"Species") >> >> mc[[1]] >> ## `[` >> >> is.primitive(`[`) >> ## [1] TRUE >> >> is.primitive(mc[[1]]) >> ## [1] FALSE >> # Expected to be TRUE >> >> mc2 <- as.call(list(`[`,iris,2,"Species")) >> >> is.primitive(mc2[[1]]) >> ## [1] TRUE >> >> So depending on how I construct the call (using call() or as.call() ), the >> function `[` is or is not recognized as a primitive by is.primitive() >> >> The behaviour is counterintuitive and -unless I miss something obvious >> here- likely to be a bug imho. I immediately admit that my C chops aren't >> sufficient to come up with a patch. >> >> Cheers >> Joris >> >> -- >> Joris Meys >> Statistical consultant >> >> Ghent University >> Faculty of Bioscience Engineering >> Department of Mathematical Modelling, Statistics and Bio-Informatics >> >> tel : +32 (0)9 264 61 79 >> joris.m...@ugent.be >> ------------------------------- >> Disclaimer : http://helpdesk.ugent.be/e-maildisclaimer.php >> >> [[alternative HTML version deleted]] >> >> ______________________________________________ >> R-devel@r-project.org mailing list >> https://stat.ethz.ch/mailman/listinfo/r-devel > > ______________________________________________ > R-devel@r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-devel ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
