> There are some things you are not really supposed to mess with in R... > Computing the index to $-constructs is one of them (trying to set up a > for loop as a call to `for` is another). It can be done, it's just > rather painful, and most likely not what you wanted in the first place. > Sorry, I was somewhat sloppy and in imprecise. For my class, I really need `$` to behave as usually [[ behaves in R. So to say, to evaluate the "name" argument. To be short, my "$" is part of an user interface (lots of checks, very slow), [[ and [ are left unattached and are part of "programing" interface for my classes.
There are not to many symbols in R to use as accessors of the internals of the objects. Wouldn't it be natural that the programmer to decide how to implement his "$" for himself? > The second argument to `$` and `$<-` is passed unevaluated and expected > to be of mode "name" (i.e., a symbol). Trying to compute it inline is > going to pass an unevaluated expression, which has mode "language". > I would expect the following to behave identically: > tv <- c(a="dsf", b="sss") > tl <- list(232) > `$<-`(tl, tv[[1]], "sdfdsfdsfsd") Error: invalid subscript type 'language' > tl$`tv[[1]]` <- "sdfdsfdsfsd" > tl [[1]] [1] 232 $`tv[[1]]` [1] "sdfdsfdsfsd" So what is relay going on? In one case the name is expected, in another case any "language" object would work? > If you insist, you can do things like > > eval(bquote(`$<-`(x, .(as.name(tv[[1]])), 4343))) > > or similar constructs using substitute(). > > However, the whole situation suggests that you are really looking for > methods for "[[<-". ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
