Duncan Murdoch <murdoch.dun...@gmail.com> writes: > Vitaly S. wrote: >> Martin Morgan <mtmor...@fhcrc.org> writes: >> >>>> So, can I be sure that for such functions parent.frame(2) will always >>>> work? >>>> What are the additional rules? >>>> >>> callNextMethod() will cause additional problems; the idea that you'll >>> grab things from somewhere other than function arguments doesn't seem >>> like a robust design, even if it's used in some important parts of R. >>> >>> Martin >>> >>> >> >> That make it difficult to handle unevaluated expressions in methods. A >> solution >> would be to explicitly require the users to use quote() or expression(), and >> then to use the "expression" in the signature. Slightly unpleasant, though. >> >> > > You could use formulas for that. If you pass in > > formula = ~ x + y*z > > then environment(formula) will be the right evaluation environment, and > formula[[2]] will be the unevaluated x + > y*z. > > Duncan Murdoch
Thank you Duncan, I didn't know that. For programmatic use though, formula interface is slightly inconvenient. A specialized function and class would be desirable. With the advent of more and more complex S4 classes, unevaluated expressions in methods calls will became a necessity, that's my feeling. Thank you. Vitaly. > >> Standardised, simpler syntax like .() in ggplot and plyr, would be handy >> here. >> Hopefully .() is not grabbed for something else in meanwhile:). >> >> Vitaly. >> >> ______________________________________________ >> 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
